read the selected sections and sumrise it in points in order to i can present it in presnration, there are emprical studies and theroies i hope you sumrise it. first articel,<\/p>\n
1.Language learning and language use in bilinguals
\n* language acquisition in bilingual children
\n* two languages in the mind
\n– lexical retrieval in bilinguals
\n– studies of verbal fluency
\n* Cognitive control and bilingual language processing
\n4. Implications of bilingualism for clinical practice
\n* Verbal fluency in clinical practice
\nthe second article just a cue about the second article.<\/p>\n
let me know if you need more than two papers or additional pages.<\/p>\n
Article
\nBilingual Minds
\nEllen Bialystok1, Fergus I.M. Craik2, David W. Green3, and
\nTamar H. Gollan4
\n1Department of Psychology, York University, 2Rotman Research Institute, Baycrest Centre, 3Department of Cognitive,
\nPerceptual, and Brain Sciences, University College London, 4University of California, San Diego
\nSummary
\nThe regular use of two languages by bilingual individuals has
\nbeen shown to have a broad impact on language and cognitive
\nfunctioning. In this monograph, we consider four aspects of this
\ninfluence.
\nIn the first section, we examine differences between monolinguals
\nand bilinguals in children\u2019s acquisition of language
\nand adults\u2019 linguistic processing, particularly in terms of
\nlexical retrieval. Children learning two languages from birth
\nfollow the same milestones for language acquisition as monolinguals
\ndo (first words, first use of grammar) but may use
\ndifferent strategies for language acquisition, and they generally
\nhave a smaller vocabulary in each language than do monolingual
\nchildren learning only a single language. Adult bilinguals
\ntypically take longer to retrieve individual words than monolinguals
\ndo, and they generate fewer words when asked to satisfy a
\nconstraint such as category membership or initial letter.
\nIn the second section, we consider the impact of bilingualism on
\nnonverbal cognitive processing in both children and adults. The
\nprimary effect in this case is the enhancement of executive control
\nfunctions in bilinguals.On tasks that require inhibition of distracting
\ninformation, switching between tasks, or holding information
\nin mind while performing a task, bilinguals of all ages outperform
\ncomparable monolinguals. A plausible reason is that bilinguals
\nrecruit control processes to manage their ongoing linguistic performance
\nand that these control processes become enhanced for
\nother unrelated aspects of cognitive processing. Preliminary evidence
\nalso suggests that the executive control advantage may even
\nmitigate cognitive decline in older age and contribute to cognitive
\nreserve, which in turn may postpone Alzheimer\u2019s disease.
\nIn the third section, we describe the brain networks that are
\nresponsible for language processing in bilinguals and demonstrate
\ntheir involvement in nonverbal executive control for
\nbilinguals. We begin by reviewing neuroimaging research that
\nidentifies the networks used for various nonverbal executive
\ncontrol tasks in the literature. These networks are used as a reference
\npoint to interpret the way in which bilinguals perform
\nboth verbal and nonverbal control tasks. The results show that
\nbilinguals manage attention to their two language systems
\nusing the same networks that are used by monolinguals
\nperforming nonverbal tasks.
\nIn the fourth section, we discuss the special circumstances
\nthat surround the referral of bilingual children (e.g., language
\ndelays) and adults (e.g., stroke) for clinical intervention. These
\nreferrals are typically based on standardized assessments that
\nuse normative data from monolingual populations, such as
\nvocabulary size and lexical retrieval. As we have seen,
\nhowever, these measures are often different for bilinguals, both
\nfor children and adults. We discuss the implications of these
\nlinguistic differences for standardized test performance and
\nclinical approaches.
\nWe conclude by considering some questions that have
\nimportant public policy implications. What are the pros and
\ncons of French or Spanish immersion educational programs,
\nfor example Also, if bilingualism confers advantages in
\ncertain respects, how about three languages\u2014do the benefits
\nincrease In the healthcare field, how can current knowledge
\nhelp in the treatment of bilingual aphasia patients following
\nstroke Given the recent increase in bilingualism as a research
\ntopic (sample nursing essay examples by the best nursing assignment writing service), answers to these and other related questions should be
\navailable in the near future.
\nIntroduction
\nAs the world becomes more interconnected, it is increasingly
\napparent that bilingualism is the rule and not the exception. Not
\nonly do some countries support bilingual populations because
\nof cultural and linguistic diversity within its citizenry, but also
\nincreased global mobility has enlarged the number of people
\nwho have become bilingual at all levels of society. For example,
\na recent survey of language use in the United States
\nobtained from the American Community Survey in 2007
\nreported that approximately 20% of the population spoke a
\nnon-English language at home, a proportion that has increased
\nby 140% since 1980 (Shin & Kominski, 2010). These numbers
\nare higher when considering world figures: Crystal (1997) estimates
\nbilingualism that includes English and another language
\nCorresponding Author:
\nEllen Bialystok, Department of Psychology, York University, 4700 Keele Street,
\nToronto, Ontario M3J 1P3, Canada
\nE-mail: ellenb@yorku.ca
\nPsychological Science in the
\nPublic Interest
\n10(3) 89\u2013129
\n\u00aa The Author(s) 2009
\nReprints and permission:
\nsagepub.com\/journalsPermissions.nav
\nDOI: 10.1177\/1529100610387084
\nhttp:\/\/psi.sagepub.com
\n89
\nrepresents about 235 million people worldwide and that two
\nthirds of the children in the world are raised in bilingual
\nenvironments.
\nRecently, evidence indicating that this common experience
\nhas a systematic and significant impact on cognitive functioning
\nhas accumulated. In this review, we examine the nature of that
\nimpact across the lifespan and consider what these effects contribute
\nto our understanding of cognition in general. We begin
\nby examining the linguistic dimensions of bilingualism in terms
\nof children\u2019s language acquisition and adult language processing.
\nIn the second section, we investigate the consequences of
\nbilingualism on nonverbal cognitive functioning. The third section
\ndescribes research documenting how the brain supports
\nbilingual functioning and how it changes in response to it. In the
\nfourth section, we review the clinical implications of bilingualism
\nfor diagnosis and intervention. We conclude by identifying
\nand discussing some specific issues for bilinguals in society. By
\nadopting this cognitive perspective, there are a number of topic (sample nursing essay examples by the best nursing assignment writing service)s
\nwe do not cover, such as reading, lexical and syntactic processing,
\nand linguistic consequences of brain damage, all of which
\nare beyond the scope of the present review.
\nThere are many ways to be bilingual: Some people are born
\nbilingual, some aspire to bilingualism, and others have bilingualism
\nthrust upon them later in life. Underlying these differences,
\na myriad of factors make the bilingual experience
\ndeeply heterogeneous and potentially alter its consequences.
\nSome of the reasons for bilingualism include immigration, a
\nfamily that speaks a heritage language, formal education in
\nanother language, temporary residence in another country, or
\na national situation in which the official language is different
\nfrom the community language. Each of these circumstances
\nis associated with a different set of social, cognitive, and personal
\nfactors, and these factors undoubtedly intervene in as
\nwell as determine any potential effect of bilingualism. Each
\nof the situations associated with multiple language use also carries
\ndifferent assumptions about expectations for education,
\nvalues around literacy, standards for language proficiency,
\nthe purposes for which one or both of the languages are used,
\nthe level of community support for the home language, and the
\nidentity of the individual as a member of a majority or minority
\nculture. Therefore, there can be no single outcome and no definitive
\nconsequence that follows from incorporating more than
\none language into daily life. And yet the consequences of
\nbilingualism affect educational policy, social organization, and
\nconceptions of mind.
\n1. Language Learning and Language Use in
\nBilinguals
\nLanguage acquisition in bilingual children
\nThe most striking feature of a young child\u2019s acquisition of
\nlanguage is the extraordinary ease withwhich the process appears
\nto progress. Perhaps more remarkable than this achievement,
\ntherefore, is that this facility for learning a complex symbolic systemis
\nnot diminishedwhen the child faces the task of learning two
\nof them. Bilingual language acquisition is as effortless, efficient,
\nand successful asmonolingual acquisition. It is nowclear that language
\nacquisition is not a simple matter of biological unfolding,
\nas some had previously believed, but rather a process that is finely
\ntuned to features of the environmental input, the child\u2019s attentional
\nand perceptual abilities, and the development of cognitive
\nand conceptual competencies. All of these factors conspire
\nas well to shape the process of acquiring two languages. Moreover,
\nas we describe later, the major milestones concerning
\ncompetence in sounds, words, and sentences that are the
\nfoundation of acquiring language are passed at equivalent
\ntimes for children growing up with one language in the home
\nand those growing up in a multilingual home.
\nThe acquisition of the phonological system by infants has
\nbeen well documented for the case of monolingual acquisition:
\nInfants can detect the contrasts that define the phonological
\nsystem for all human languages almost from birth (e.g., \/pa\/
\nvs. \/ba\/; Eimas, Siqueland, Jusczyk, & Vigorito, 1971), but
\ntheir ability to perceive these contrasts in languages that are not
\nheard in the environment (e.g., \/r\/ vs. \/l\/ for children being
\nraised in Japanese homes) begins to decline at about 6 months
\nof age (Werker & Tees, 1984; see also Kuhl et al., 2006). Thus,
\nuntil about 6 months old, there is no detectable difference in the
\nperception of phonetic contrasts by infants in monolingual and
\nbilingual environments but diverging patterns appear as bilingual
\nbabies maintain and develop the categorical distinctions
\nfor the phonetic system in both languages and monolingual
\ninfants lose the ability to detect contrasts that are not part of the
\nlanguage they are about to learn (Burns, Yoshida, Hill, &
\nWerker, 2007; Sebastian-Galles & Bosch, 2005). By about
\n14 months old, infants being raised in bilingual environments
\nhave established a clearly demarcated phonological representation
\nfor both languages. Therefore, bilingual infants develop
\nthe phonological basis for both languages on roughly the same
\nschedule as monolingual children do for their only language.
\nIt may be that it is this very early experience that leaves its lifelong
\ntrace as a foreign accent when childhood monolinguals
\nattempt to learn new languages later in life.
\nBeyond the phonetic constituents, infants also need to learn
\nthe more general phonological structure of language. Recently,
\nKovacs and Mehler (2009a) presented auditory stimuli to
\n12-month-old infants who were being raised in a monolingual
\nor bilingual environment. The stimuli were three-syllable
\ncombinations that had the syllabic structure of either ABA or
\nAAB. These stimuli were artificial creations and were not
\nwords in any language. The crucial manipulation was that each
\nstructure was associated with a different response\u2014namely,
\nlook either to the right or to the left to see an interesting toy.
\nThe experimental results showed that the monolingual babies
\ncould learn only one of the responses but that the bilingual
\nbabies learned both, a difference the researchers interpreted
\nas demonstrating more flexible learning in bilinguals. They
\noffer their results as part of the explanation for how bilingual
\nchildren can learn twice as much about language as monolingual
\nchildren in the same amount of time (although it is not
\nclear that they do, as will be discussed below), but the task was
\n90 Bialystok et al.
\n90
\nonly marginally linguistic. If anything, it is more similar to
\nword learning than to speech perception, a process that rests
\non different perceptual and cognitive processes than phonological
\ndevelopment (Burns et al., 2007). In fact, bilingual babies
\napply their developing phonological system to the learning of
\nnew words later than monolingual children do (Fennell,
\nByers-Heinlein, & Werker, 2007), although a recent study
\ntesting 17-month-old infants raised with French and English
\ndid not replicate this finding and attributed the difference
\nbetween studies to details of the phonetic input (Mattock,
\nPolka, Rvachew, & Krehm, 2010). Nonetheless, the results
\nreported by Kovacs and Mehler provide compelling evidence
\nfor different levels of performance in a phonological task in the
\nfirst year of life that can be traced to the experience of building
\nup two linguistic systems.
\nUndoubtedly the most salient evidence for children\u2019s
\nprogress in language acquisition is word learning, particularly
\nthe appearance of the child\u2019s first word. As with the developing
\nphonological system, the basic milestones associated with this
\nachievement are similar for children learning one or more
\nlanguages. The child\u2019s first word appears on average at about
\n1 year old, regardless of how many languages are in the
\nenvironment (Pearson, Fernandez, & Oller, 1993) and, more
\ndramatically, regardless of whether the languages are both
\nspoken or one is spoken and one is signed (Petitto et al.,
\n2001). However, two factors may be different for monolingual
\nand bilingual children: the strategies for word learning and the
\nrate and extent of vocabulary acquisition.
\nOne strategy that allows children to rapidly learn new words
\nis to assume that novel words signify unfamiliar objects,
\npresenting a simple pairing of word and concept. This strategy
\nof word\u2013meaning assignment follows from what Markman and
\nWachtel (1988) posit as the mutual exclusivity constraint\u2014the
\nassumption that a thing can only have one name\u2014although this
\nassumption need not be innately determined. The evidence for
\nmutual exclusivity is that children appear to create mappings
\nbetween new words and new objects\u2014for example, if a child
\nhears the word \u2018\u2018bik\u2019\u2019 while looking at a cup and an unknown
\nobject, the child will assume that the novel item is called a bik.
\nBut bilingual children already know that things can have more
\nthan one name\u2014the known object could be \u2018\u2018a cup\u2019\u2019 or \u2018\u2018une
\ntasse.\u2019\u2019 Do bilingual children follow the strategy of mapping
\nunknown words to unknown objects The evidence is mixed,
\nwith some studies reporting less reliance on this strategy for
\nbilingual children (Bialystok, Barac, Blaye, & Poulin-Dubois,
\n2010; Davidson & Tell, 2005) but others reporting
\nno difference between monolingual and bilingual children
\n(Au & Glusman, 1990; Merriman & Kutlesic, 1993). More convincing,
\nhowever, is evidence from a study by Byers-Heinlein
\nand Werker (2009) in which they compared the adherence to
\nthis strategy by children learning one, two, or three languages.
\nTheir results showed a systematic decline in the reliance on this
\nheuristic with the number of languages being learned. These
\nresults, in conjunction with those reported by Kovacs and
\nMehler (2009a) suggesting that phonological word structures
\nare perceived differently by monolingual and bilingual
\nchildren, are consistent with a view in which the actual
\nmechanisms of word learning used by monolingual children
\ndiffer from those used by bilingual children. Importantly,
\nhowever, the essential cognitive landmark that guides these
\nmechanisms, namely, the time at which the child is able to produce
\nthe first meaningful word, is comparable for all children.
\nThe second difference in word learning between monolingual
\nand bilingual children is in the size of their developing
\nvocabularies. As in phonological discrimination and first word
\nproduction, the timetable for the critical milestone is similar for
\nchildren with both types of experience. In this case, the crucial
\nlandmark is the establishment of a vocabulary of 50 words,
\nwhich is achieved by both monolingual and bilingual children
\nat about 1\u00bd years old (Pearson et al., 1993; Petitto, 1987;
\nPetitto et al., 2001), at least for total vocabulary across the two
\nlanguages. Beyond that, however, the evidence is compelling
\nthat, on average, bilingual children know significantly fewer
\nwords in each language than comparable monolingual children.
\nA careful investigation examining how many words children
\nbetween 8 and 30 months old knew in each language confirmed
\nthat, on average, this number was smaller in each language for
\nbilingual children than for monolingual learners of that
\nlanguage (Pearson et al., 1993). The number of words in the
\ntotal vocabulary of a bilingual child, however, is difficult to
\nestimate: Do proper names count for one language or two
\nDo cognates count once or twice, especially if the pronunciation
\nis unclear Do childish sounds that are not quite words
\ncount as words if they have a consistent meaning
\nA clearer illustration of the relative vocabulary size of
\nmonolinguals and bilinguals comes from a study of children
\nwho were older than those in the Pearson et al. (1993) analysis.
\nBialystok, Luk, Peets, and Yang (2010) measured the receptive
\nvocabulary of over 1,700 children between the ages of 3 and
\n10 years old. All the bilingual children spoke English and
\nanother language, with English being the language of the community
\nand school for all children. Across the sample and at
\nevery age studied, the mean standard score on the English Peabody
\nPicture Vocabulary Test (PPVT) of receptive vocabulary
\n(Dunn & Dunn, 1997) was reliably higher for monolinguals
\nthan for bilinguals. These results are shown in Figure 1. At least
\nin one of the two languages and, importantly, the language of
\nschooling, monolingual children had an average receptive
\nvocabulary score that was consistently higher than that of their
\nbilingual peers. It is important to note, however, that the disparities
\nwere not equivalent for all words. In a subset of 6-yearolds
\nin the sample, all children achieved comparable scores
\non words associated with schooling (e.g., astronaut, rectangle,
\nwriting) but bilinguals obtained significantly lower scores for
\nwords associated with home (e.g., squash, canoe, pitcher).
\nTherefore, the nature of the smaller vocabulary of bilingual
\nspeakers of each language than that of monolingual speakers
\nis in fact somewhat complex (Bialystok, Luk, et al., 2010).
\nThe hallmark of human language, however, is not sounds or
\nwords, but the grammatically constrained combinations of
\nunits to form utterances or sentences. Again, the transition into
\nthis stage of language acquisition occurs on the same timetable
\nBilingual Minds 91
\n91
\nfor children learning one or more languages: The first word
\ncombinations for all children appear at about 1\u00bd years old
\n(Pearson et al., 1993; Petitto et al., 2001), with utterances becoming
\nincrementally more complex on a similar trajectory (de
\nHouwer, 1995). The details of children\u2019s increasing grammatical
\nsophistication appear to be tied to the specific language, with
\nexamples for this point coming from children learning English
\nand Spanish (Gathercole, 1997), English and French (Paradis &
\nGenesee, 1996), and French and German (Meisel, 1990).
\nCurrent theories of language acquisition are based on the
\nidea that there is a deep connection between words and
\nstructure: Grammar is part of the linguistic system and emerges
\nseamlessly when the lexicon has reached a critical mass. The
\nfirst evidence for structure occurs when the child knows about
\n50 words, a relationship demonstrated for both monolingual
\n(Bates & Goodman, 1997) and bilingual (Conboy & Thal,
\n2006) children. In this sense, discussion of children\u2019s early
\ngrammar is not different in kind from the discussion of their
\nearly lexicon, but the issues in their development present themselves
\nin different ways. And if language acquisition is not
\nguided by dedicated modules equipped to detect and record
\ngrammatical structure, then what directs this process From the
\ncognitive perspective, the linguistic and cognitive systems are
\nintimately interconnected, each guiding the other and profiting
\nfrom the symbiotic relationship. What happens when a child is
\nlearning two languages
\nAcross the major linguistic features\u2014sounds, words,
\ngrammar\u2014the acquisition of language by monolingual and
\nbilingual children follows a similar timetable for milestones that
\nlargely reflect cognitive ability, but the linguistic competence
\nthat is developing is different. Partly because linguistic
\nknowledge for bilingual children is divided across two
\nlanguages, the organization and richness of the representational
\nsystem in each language is different from that acquired by a
\nmonolingual speaker of one of the languages. Similarities in
\ndeveloping cognitive abilities keep the process of language
\nacquisition on a common time course, but variation in input and
\nuse make the developing linguistic systems quite different
\nboth qualitatively and quantitatively. Understanding bilingual
\nlanguage ability and the bilingual mind more broadly requires
\nunderstanding these interfaces between the linguistic and
\ncognitive systems.
\nTwo languages in the mind
\nThe bilingual mind presents an intriguing set of puzzles. Are
\nthe two languages represented in separate or in overlapping
\nsystems Are concepts duplicated or shared across languages
\nDo interactions between languages facilitate or impede
\nlanguage production How are the selection of the target
\nlanguage and avoidance of the nontarget language achieved
\nHow does the bilingual switch between languages, both intentionally
\nand unintentionally None of these questions applies to
\nmonolingual language use, so from the outset, the presence of
\ntwo languages in mind changes fundamental aspects of language
\nprocessing. Moreover, these questions are all inherently
\nabout cognitive systems at least as much as they are about
\nlinguistic ones; switching between representational systems
\nand avoiding interference are processes routinely handled by
\nthe general executive control system. Therefore, bilingual
\nlanguage use must be intimately tied to a cognitive system in
\na way that is less essential for monolingual speech. It is those
\n70
\n80
\n90
\n100
\n110
\n120
\n130
\n3 years
\nM=91
\nB=40
\n4 years
\nM=78
\nB=72
\n5 years
\nM=155
\nB=143
\n6 years
\nM=272
\nB=458
\n7 years
\nM=109
\nB=116
\n8 years
\nM=71
\nB=85
\n9 years
\nM=16
\nB=37
\n10 years
\nM=20
\nB=15
\nAge Group
\nMean PPVT std. score
\nMonolinguals Bilinguals
\nFig. 1. Mean Peabody Picture Vocabulary Test (PPVT) standard score and standard error by age and language group
\n(monolinguals, M, vs. bilinguals, B). From Bialystok, Luk, Peets, and Yang (2010).
\n92 Bialystok et al.
\n92
\nrelations between language and cognition that will be examined
\nin this section: How is language processing different when there
\nare two fully elaborated linguistic systems available How does
\nthat situation change the cognitive processes whose responsibility
\nit is to manage those language systems There is an active
\nbody of research examining these questions, comparing how
\nbilinguals can carry out these tasks in their two languages (for
\nexcellent reviews of this literature, see Kroll & de Groot,
\n2005). However, the present question is not to compare processing
\nof the two languages of bilingual speakers but to compare
\nmonolinguals and bilinguals as they perform similar tasks.
\nTo understand how the simple act of speaking may be
\ndifferent for monolinguals and bilinguals, it is necessary to
\nacknowledge two crucial differences between these groups.
\nFirst, the knowledge base from which all language processing
\nproceeds is less rich or less interconnected for a bilingual in
\neach language than it is for a monolingual speaker of one of
\nthose languages. The most salient difference in the language
\ncompetence of monolingual and bilingual children is in the
\nvocabulary scores obtained in a given language, as described
\nearlier (Bialystok, Luk, et al., 2010)\u2014a pattern that may persist
\ninto adulthood. Although it is more difficult to attribute reliable
\ndifferences in adults\u2019 vocabulary size to bilingualism versus
\nmonolingualism than it is for that of children because of the
\nenormous variation in adults\u2019 knowledge of words, there is nonetheless
\nevidence that such systematic differences exist (e.g., Bialystok,
\nCraik, & Luk, 2008a; Portocarrero, Burright, &
\nDonovick, 2007). Gollan and colleagues argue that the essential
\nfeature of bilingual representations is the \u2018\u2018weaker links\u2019\u2019 that are
\nestablished within the network because of less frequent use of
\neach language (Gollan, Montoya, Cera, & Sandoval, 2008); simply
\nusing each language less often produces weaker connections
\nin the network than would emerge from greater use. In this view,
\nthe knowledge resources underlying language performance for
\nmonolinguals and bilinguals who are comparable on many other
\ncognitive abilities are not equivalent.
\nSecond, it is now well documented that both languages of a
\nbilingual are jointly activated even in contexts that strongly
\nbias towards only one of them. Evidence for this claim comes
\nfrom both behavioral (Beauvillain & Grainger, 1987; Colome\u00b4,
\n2001; Grainger, 1993; Hernandez, Bates, & Avila, 1996;
\nFrancis, 1999; Kroll & de Groot, 1997) and imaging studies
\n(Marian, Spivey, & Hirsch, 2003; Martin, Dering, Thomas, &
\nThierry, 2009; Rodriguez-Fornells, Rotte, Heinze, Nosselt, &
\nMunte, 2002). One of the first pieces of evidence for this
\nconclusion comes from an ingenious experiment by Guttentag,
\nHaith, Goodman, and Hauch (1984, Experiment 2). On each
\ntrial, bilingual participants viewed a word drawn from one of
\nfour semantic categories (e.g., metals, clothing, furniture, and
\ntrees); two categories were assigned to one response key and
\nthe other two categories to a second key. The participant\u2019s task
\nwas to press the designated key to indicate the category membership
\nof the target word as rapidly as possible. Each stimulus
\nword also had copies of a further word above and below it as
\nflanker items. These flankers were always in the participant\u2019s
\nother language and belonged to one of four categories:
\ntranslations of the target word, a different word drawn from the
\nsame semantic category as the target, a word from a different
\ncategory but requiring the same response, or a word from a
\ncategory requiring a different response. The crucial result is
\nthat response times were significantly longer in the second two
\nconditions, showing that participants were unable to ignore the
\nflankers and that some analysis of the flankers\u2019 categories
\n(and possibly responses) took place despite the fact that the
\nflankers were in the nonused language.
\nThis joint activation of the two languages creates a unique
\nneed for selection in bilinguals in which language processing
\nmust resolve competition not only from within-language
\nalternatives as monolinguals do to select among close semantic
\nneighbors (words that share semantic features, e.g., cup vs. mug;
\nLuce & Large, 2001; Mirman & Magnuson, 2008; Vitevitch,
\n2002) but also from between-language alternatives for the same
\nconcepts (e.g., cup vs. tasse). The predominant view is that language
\nselection does not normally occur prior to speech, making
\nthis selection part of bilingual speech production (Kroll, Bobb,
\n& Wodniecka, 2006). For this reason, a somewhat different set
\nof attention and control procedures is necessary for speech production
\nin bilinguals than is necessary for monolinguals (Green,
\n1998). However, there is less agreement on what those special
\nprocesses might be. Some studies have shown that the nontarget
\nlanguage is actually inhibited while using the other language
\n(e.g., Levy, McVeigh, Marful, & Anderson, 2007; Philipp &
\nKoch, 2009), but others indicate that correct selection can be
\nachieved by increasing the activation of the preferred response
\n(Costa, Santesteban, & Ivanova, 2006; see Costa, 2005, for a discussion
\nof these views). As we describe later, these alternatives
\nneed not be mutually exclusive: Selection depends on the activation
\nlevel of both the target item to be selected and that of the
\ncompeting items, incorporating as well views that reject the role
\nof competition and instead focus on selection (Caramazza, 1997;
\nLa Heij, 1988; Mahon, Costa, Peterson, Vargas, & Caramazza,
\n2007; Roelofs, 2003). Therefore, selection is facilitated by either
\npreferentially enhanced activation of the target, inhibition of the
\ncompetitor, or both. Whatever the mechanism, selection of
\nappropriate lexical items for bilinguals involves either
\ndifferent or additional processes than does the same activity for
\nmonolinguals. Taken together, the differences in the linguistic
\nrepresentations and differences in the selection mechanisms lead
\nto sustained differences between monolinguals and bilinguals in
\nfluent speech production.
\nAlthough ordinary conversation does not generally signal
\nobservable deficits in bilingual language processing, controlled
\nexperimental procedures can reveal more subtle differences
\nbetween these two groups. Two such features are the speed
\nwith which target words can be retrieved in response to a cue
\nand the number of words that can be generated to satisfy a
\ncriterion. Evidence for the first comes primarily from studies
\nof picture naming or semantic classification, and evidence for
\nthe second comes from studies of verbal fluency.
\nLexical retrieval in bilinguals. Much of the research in lexical
\nretrieval compares the relative ability of multilingual speakers
\nBilingual Minds 93
\n93
\nto perform such tasks as naming the pictures in their two (or
\nmore) languages (Costa & Santesteban, 2004; Hernandez,
\nMartinez, & Kohnert, 2000), making semantic classifications
\nfor words in the two languages (Dufour & Kroll, 1995), or
\ntranslating between languages (Kroll & Stewart, 1994). The
\npurpose is to compare lexical access to the two languages and,
\nin some cases, as in the study by Dufour and Kroll (1995), to
\ncompare bilinguals who are more or less fluent in the two
\nlanguages. The issue we are discussing here is different: to
\ncompare monolingual and bilingual speakers naming pictures
\nin the same language. The comparison is inherently fraught
\nwith difficulty: If we assume that bilinguals never have identical
\nproficiency in their two languages and, moreover, that even
\ntheir ability in their stronger language may not fully resemble
\nthe language competence of a monolingual speaker of that
\nlanguage, then any comparison of monolinguals and bilinguals
\nseems unfair. And yet, proficient bilinguals manage to function
\nperfectly well, belying the notion of an underlying handicap.
\nThus it may be that the task of rapidly accessing target lexical
\nitems is carried out differently by monolinguals and bilinguals,
\nan outcome that would be important in understanding
\nthe relation between language and cognitive systems in the
\nbilingual mind.
\nResearch shows that bilingual participants take longer and
\nmake more errors than monolinguals on naming tasks. Using
\nthe Boston Naming Task (Kaplan, Goodglass, & Weintraub,
\n1983), bilinguals produced fewer correct responses (Roberts,
\nGarcia, Desrochers, & Hernandez, 2002; Gollan, Fennema-
\nNotestine, Montoya, & Jernigan, 2007) and made more errors
\non a speeded version of the task (Bialystok et al., 2008a) than
\ndid monolinguals. On timed picture naming, bilinguals
\nperformed more slowly than did monolinguals (Gollan,
\nMontoya, Fennema-Notestine, & Morris, 2005). Similar results
\n(slower responses in bilinguals) are found in both comprehending
\n(Ransdell & Fischler, 1987) and producing words (Ivanova
\n& Costa, 2008), even when bilinguals respond in their first and
\ndominant language. The simple act of retrieving a common
\nword seems to be more effortful for bilinguals.
\nHealthy aging is frequently accompanied by a reduction in
\nproductive language abilities\u2014searching for words and names
\nbecomes a more salient part of every conversation. Consistent
\nwith this trend, picture naming is carried out more slowly by
\nolder adults than by younger adults, even for monolinguals
\n(e.g., Albert, Heller, & Milberg, 1988). Therefore, older
\nbilinguals should find lexical access particularly difficult, since
\nboth age and language status are associated with poorer
\nperformance. The situation is even more problematic for older
\nbilinguals who may have spent the majority of their adult lives
\nusing one of their two languages, usually the second language
\n(L2), and have been removed from a daily context that supports
\nthe first language (L1). The outcome of this situation can be
\nattrition of the L1. Therefore, difficulties in performance on
\ntests of lexical access such as picture naming can be attributable
\nto normal aging, L1 attrition, or both. These possibilities
\nwere evaluated in a study by Goral, Libben, Obler, Jarema, and
\nOhayon (2008) comparing younger and older Hebrew-English
\nbilinguals who lived in an English-speaking or Hebrewspeaking
\nsociety. Their conclusion was that the slower retrieval
\ntime for older bilingual adults in their L1 was caused primarily
\nby attrition of that language and not by aging. These results
\npoint to the importance of gauging proficiency level, such as
\nvocabulary knowledge, in linguistic processing and in performance
\non psycholinguistic tasks.
\nLinguistic differences between monolinguals and bilinguals
\ngo beyond vocabulary size. The consistent result showing
\nlonger picture-naming times for bilinguals suggests that word
\nretrieval is carried out differently for bilinguals than for
\nmonolinguals. To explore a possible explanation for this effect,
\nHernandez and Meschyan (2006) conducted a functional
\nmagnetic resonance imaging (fMRI) study in which Spanish-
\nEnglish bilinguals who learned the L2 in adolescence named
\npictures in both languages. The results showed that naming the
\npictures in the weaker second language produced greater
\nactivity in the executive control network, a system that will
\nbe described in more detail in Sections 2 and 3. Extrapolating
\nto monolingual performance, where naming is always carried
\nout in a strong language, it appears that this executive control
\nnetwork is involved in word retrieval for bilinguals in a way not
\nrequired by monolingual language production. We will return
\nto this idea later.
\nStudies of verbal fluency. The second experimental paradigm
\nin which reliable differences between monolinguals and
\nbilinguals have been reported is the verbal fluency task. The
\nbasic procedure is to ask participants to generate as many words
\nas possible in 60 seconds that satisfy a criterion determined
\neither by the category (semantic fluency) or the initial letter of
\nthe word (phonological fluency). There are standardized versions
\nof the task, such as in the Delis-Kaplan Executive Function
\nBattery (DKEFS; Delis, Kaplan, & Kramer, 2001) and the
\nControlled Oral Word Association Test (COWAT; Strauss,
\nSherman, & Spreen, 2006), that allow performance to be interpreted
\nin terms of normalized tables and used as an instrument
\nfor neuropsychological assessment. The clinical applications of
\nthis test are explained in Section 4, but in the present discussion
\nwe consider the task as an experimental tool. The semantic and
\nletter versions assess different aspects of competence and engage
\ndifferent processes. The demands of category fluency are
\ncongruent with normal procedures for word retrieval in that the
\nmeaning is cued and words associated with that meaning are
\nprimed and available. Thus, when asked to generate names of
\nfruits, the inherent associations among various fruits in semantic
\nmemory facilitate recall. In contrast, the letter fluency condition
\nimposes an arbitrary criterion on word generation: Conversation
\ndoes not normally require the generation of words by virtue of
\ntheir initial letter. Moreover, the letter fluency task additionally
\nimposes a set of restrictions that exclude repetitions of words in
\ndifferent forms and therefore requires more intensive monitoring
\nand working memory. Thus, category fluency is strongly indicative
\nof vocabulary size (how many types of fruit can you name)
\nand letter fluency requires additional and effortful procedures for
\nmonitoring and controlling attention (how well can you keep
\n94 Bialystok et al.
\n94
\ntrack of the words already produced and initiate a new search to
\nsatisfy a different criterion). Supporting this interpretation of
\ndistinct processes involved in each condition, Grogan, Green,
\nAli, Crinion, and Price (2009) related the results of structural
\nMRI scans of high-proficiency bilinguals to their performance
\non category and letter fluency tasks. They found that grey matter
\ndensity in a medial frontal region (the presupplementary motor
\narea) and one subcortical region (the left caudate; see Section
\n3 for the neural bases of language control) was related to letter
\nfluency performance whereas higher grey matter density in left
\ninferior temporal cortex was related to semantic fluency
\nperformance.
\nThe typical outcome of studies comparing monolingual and
\nbilingual adults performing verbal fluency tasks is for bilinguals
\nto generate fewer words than monolinguals, with greater
\ndisparity between groups in the category fluency task (Bialystok
\net al., 2008a; Gollan, Montoya, & Werner, 2002; Portocarrero
\net al., 2007; Rosselli et al., 2000). In a dramatic demonstration,
\nLinck, Kroll, and Sunderman (2009) reported that Englishspeaking
\ncollege students living in a Spanish-speaking environment
\nfor 1 year produced fewer words on a verbal fluency test in
\nEnglish than did monolinguals who did not travel abroad! The
\nscores of the students who had been abroad were restored shortly
\nafter returning home. Moreover, as with picture naming
\n(Connor, Spiro, Obler, & Albert, 2004), performance in verbal
\nfluency declines with healthy aging, so this task may be especially
\ndifficult for older bilingual adults (Brickman et al., 2005).
\nSeveral possible reasons for the difference in verbal fluency
\nbetween monolinguals and bilinguals have been suggested.
\nFirst, bilinguals may simply have a smaller overall vocabulary
\nthan monolinguals in each language, a deficit that would particularly
\naffect the category fluency test. Indeed, it is primarily on
\ncategory fluency that lower scores for bilinguals have been
\nmost often observed, with some researchers reporting no difference
\nbetween groups in letter fluency (e.g., Rosselli et al.,
\n2000). Second, as demonstrated in the research on picture
\nnaming, bilinguals take longer to retrieve each item, so the
\n60-second limit in a verbal fluency trial may curtail bilingual
\nperformance. One possible reason for slower word retrieval
\nin bilinguals is the need to deal with the competition from the
\nother language, as stated earlier. Managing this competition
\ntakes time, and this can delay word production for bilinguals and
\nresult in fewer words being generated. Note that both of these
\nreasons\u2014vocabulary limitations and competition resolution\u2014
\napply primarily to category fluency where multiple exemplars
\nfor the given category are activated, including exemplars from
\nthe nontarget language, and much less to letter fluency. In contrast,
\nletter fluency relies less on the richness of vocabulary in a
\nsemantic domain and the automatic activation of exemplars in
\nthe other language. Therefore, there is no reason to expect monolinguals
\nand bilinguals to perform differently on letter fluency
\ntasks. In fact, the additional requirements for working memory
\nand monitoring in the letter fluency condition should actually
\nfavor bilinguals who, as will be explained later in Section 2, are
\ngenerally better than monolinguals in tasks requiring working
\nmemory and monitoring.
\nA more detailed understanding of performance on the verbal
\nfluency task comes from examining the function showing the
\nproduction of words in real time across the 1 minute allotted
\nto each trial. Following the logic explained by Rohrer, Wixted,
\nSalmon, and Butters (1995), a deficit in vocabulary size should
\nmanifest itself in a function that shows very few words being
\nproduced toward the end of the time period because the potential
\nset of items has been exhausted. In this case, monolinguals
\nwould continue producing words later into the time course than
\nwould bilinguals. In contrast, slower time to produce each item,
\npossibly because of the need to resolve competition from the
\nnontarget language, would produce a function that continues
\nlonger into the time period than one representing faster retrieval
\nof the same total number of words. In this case, bilinguals
\nwould produce words later in the time course than
\nmonolinguals.
\nThese predictions were tested in two studies using timecourse
\nanalysis to compare monolinguals and bilinguals performing
\na verbal fluency task. A study by Sandoval, Gollan,
\nFerreira, and Salmon (2010) compared monolinguals and
\nSpanish-English bilinguals who reported high proficiency in
\nboth languages for their performance on several category and
\nletter fluency conditions in English, and in a second experiment
\nalso compared the time course of retrieval from bilinguals\u2019 two
\nlanguages (English vs. Spanish). In another study by Luo, Luk,
\nand Bialystok (2010), a standardized version of the category
\nand letter fluency tasks in English was administered to monolinguals
\nand bilinguals who were either matched on English
\nvocabulary or had a lower English receptive vocabulary. In
\nboth studies, the bilinguals produced words later into the
\nallotted time, indicating slower and more effortful retrieval for
\neach word produced, likely due to interference from the nontarget
\nlanguage (Sandoval et al., 2010). In addition, the comparison
\nbetween the two English proficiency groups in the study by
\nLuo et al. indicated a second effect attributable to vocabulary
\nsize. Once vocabulary was matched, the bilinguals with English
\nproficiency comparable to that of monolinguals performed
\nas well as the monolinguals on the category fluency task and
\nbetter than monolinguals on letter fluency. Having equated for
\ndifferences in vocabulary resources, the bilinguals were able to
\ndisplay better control than the monolinguals in the condition
\nthat required monitoring and working memory. Figure 2a displays
\nthe results for category fluency in which monolinguals and
\nhigh-vocabulary bilinguals show identical retrieval patterns
\nbecause performance is driven primarily by vocabulary size,
\nwhich in this case is matched. Figure 2b displays the results for
\nletter fluency; in this case, the high-vocabulary bilinguals maintain
\na higher production rate throughout the time course than do
\nthe other two groups because the task additionally requires high
\nlevels of executive control.
\nThese results point to the need to guarantee that participants
\nwho are performing a language task have linguistic resources
\nadequate to carry out the task. Without explicitly controlling
\nfor language proficiency, it is impossible to localize the effects
\nof bilingualism as opposed to the effects of weaker proficiency
\nin the language of testing. Moreover, when proficiency in the
\nBilingual Minds 95
\n95
\ntwo languages had been controlled by using receptive vocabulary
\nas a matching variable, a bilingual advantage emerged in
\nthe letter fluency task. This pattern was replicated in a
\ncomparison between monolinguals, bilinguals with matched
\nvocabulary, and bilinguals with lower vocabulary on a simple
\nbehavioral comparison of the number of words produced in
\neach of these fluency tasks (Bialystok, Craik, & Luk, 2008b).
\nClearly, not all tasks requiring processing of linguistic material
\nare performed more poorly by bilinguals.
\nControl over linguistic resources. To this point, the studies
\ndescribed have generally found more effortful (longer response
\nFig. 2. Number of items produced as a function of time in (A) category task and (B) letter task
\nfor monolinguals, high-vocabulary (HV) bilinguals, and low-vocabulary (LV) bilinguals. Best fit
\nlines are logarithmic functions. From Luo, Luk, and Bialystok (2010).
\n96 Bialystok et al.
\n96
\ntime, RT) or poorer (more errors) performance by bilinguals
\nthan by monolinguals when rapid retrieval of specific lexical
\nitems is required. When language proficiency is matched,
\nhowever, bilinguals perform as well as monolinguals in
\ncategory fluency (which depends on vocabulary) and better
\nthan monolinguals on letter fluency (which depends more
\nextensively on cognitive control). Therefore, at least some of
\nthe differences observed between monolinguals and bilinguals
\non language production tasks reflect a simple difference
\nin linguistic resources and may mask a potential advantage in
\ncontrol over those resources once proficiency has been equated.
\nIf bilinguals do have better control over linguistic resources
\nthan do monolinguals, then it should be possible to demonstrate
\nthis processing difference in tasks that require monitoring or
\nmanipulation of verbal stimuli. Two tasks meet these criteria.
\nThe first is a paradigm developed by Jacoby (1991), called the
\nprocess dissociation procedure (PDP), that is designed to
\ndistinguish between automatic (familiarity) and controlled
\n(recollection) aspects of memory. The second is a paradigm
\ncalled release from proactive inhibition (PI) that assesses the
\nability to monitor items for their source (e.g., Kane & Engle,
\n2000). Both paradigms have been widely used in studies of cognitive
\nprocesses involved in memory performance. Although
\nsubstantially different from each other, they share the feature
\nthat participants are asked to remember words for later recall
\nwhen an intervening event has made it difficult to keep track
\nof the source of the target words. In the case of PDP, words are
\npresented in two lists, or two formats (for example, visually or
\norally), and the crucial recall test requires responding only to the
\nwords presented in one of them (for example, visually) and
\nignoring the others. In the case of PI, lists of different words
\nfrom the same semantic category are presented successively and
\nparticipants are asked to report the words on the list just heard
\nwithout reporting words from the previous lists. \u2018\u2018Release\u2019\u2019 from
\nPI is observed when words from a different category are presented.
\nBoth tasks, therefore, require monitoring and control to
\nattend to the target words and inhibition to avoid making errors
\non the distractor words. As predicted, bilinguals obtained lower
\nscores than monolinguals on tests of receptive vocabulary but
\nperformed better than monolinguals on both PDP (Wodniecka,
\nCraik, Luo, & Bialystok, 2010) and release from PI tasks
\n(Bialystok & Feng, 2009). Again, separating verbal ability
\nfrom control over verbal processing produces a more complex
\npicture in which bilinguals demonstrate better processing in
\nthe context of poorer verbal performance.
\nCognitive control and bilingual language
\nprocessing
\nAll the illustrations of language acquisition and use described
\nin this section have demonstrated the importance of considering
\nthe interaction between language and cognitive systems in
\nexplaining outcomes for bilinguals. Bilingual children acquire
\nlanguage on the same timetable as monolingual children, largely
\nbecause this timetable is determined by the process of cognitive
\ndevelopment. As acquisition proceeds, however, bilingual
\nchildren develop different types of competence (e.g., smaller
\nvocabulary in each language) and probably use different
\nstrategies (e.g., phonemic cues and mutual exclusivity for word
\nlearning). In adulthood, the ability of bilinguals to effectively
\nuse language in such tasks as word retrieval and word generation
\ndepends on both linguistic competence and cognitive procedures
\nfor access and monitoring. Thus, levels of vocabulary
\ndetermine how many words can be associated with a meaningful
\ncategory but levels of control determine how many words can be
\nselected to fit an arbitrary restrictive criterion.
\nWhat is the source of these interactions One possibility is
\nthat the interacting systems are set in motion because the joint
\nactivation of the two languages for a bilingual creates a problem
\nnot experienced by monolinguals\u2014namely, the need to select
\nfrom the target system in the context of compelling and active
\nalternatives. There is substantial evidence, described in Sections
\n2 and 3, that the response to this conflict is to recruit the executive
\ncontrol system that has evolved to resolve conflict across all
\ndomains of perceptual and cognitive processing. The constant
\nuse of this executive control system for bilingual language management
\nopens the possibility that the system itself is modified,
\nchanging its valence or efficiency for all tasks. That is, the use of
\na set of executive control procedures to manage attention to language,
\nto avoid interference from the nontarget language, and to
\nmonitor two simultaneously active languages may alter the
\nnature or efficiency of those executive control processes more
\ngenerally. This possibility is examined in the next section. To
\nanticipate, the evidence suggests that whereas bilingual children
\nand adults have somewhat lower vocabulary levels than their
\nmonolingual counterparts, the bilinguals possess an advantage
\nin cognitive control that generalizes beyond language processing
\nto other aspects of cognitive functioning.
\n2. How Bilingualism Affects Cognitive
\nControl
\nFor many years it was assumed that while bilingualism might
\nbe an asset for adults\u2014in terms of culture, travel, and trade,
\nfor example\u2014it was a handicap for children in the educational
\nsystem. The idea was that learning in two languages imposed
\nan additional burden on schoolchildren who must learn two
\nvocabularies, two sets of grammar, and probably two sets of
\ncultural habits and expectations. This negative view of bilingualism
\nwas at least questioned by the results of a study by
\nPeal and Lambert (1962). They gave a battery of intelligence
\ntests to French-speaking children in Montreal who were also
\nfluent English speakers. They expected to find that monolingual
\nand bilingual children would be equivalent on measures
\nof nonverbal intelligence but that bilinguals would obtain
\nlower scores on verbal measures. To their surprise, however,
\nbilingual children outperformed their monolingual peers on
\nvirtually all of the tests, including tests of nonverbal intelligence.
\nFurther analysis revealed that there was little difference
\nbetween the groups on spatial-perceptual tests but that
\nthe bilingual children showed an advantage on tests requiring
\nsymbol manipulation and reorganization. This latter finding
\nBilingual Minds 97
\n97
\nhas the interesting implication that extra effort and more
\nextensive learning in the area of language apparently confers
\nbenefits to nonverbal mental abilities, refuting the idea that
\nlanguage is a separate module of mind and brain that relies
\non dedicated processes (e.g., Fodor, 1983); instead, language
\nmust be viewed as recruiting processes from the general cognitive
\nsystem. On the basis of their unexpected findings, Peal and
\nLambert suggested that bilingual children may show enhanced
\nmental flexibility, perhaps as a consequence of having to
\nswitch between their two languages.
\nThe study by Peal and Lambert (1962) may be criticized on
\nthe grounds that francophone children in Montreal in 1960 who
\nspoke English were likely of higher than average social class,
\nor at least were the children of intelligent and ambitious
\nparents, and were therefore less representative than their monolingual
\ncounterparts (Bialystok, 2001). Nevertheless, the study
\nwas important in showing both that bilingualism in children
\nmight help rather than hinder the development of other abilities
\nand also that language learning may influence nonverbal
\ncognitive processes supporting the view that language is not
\na separate and independent module of mind.
\nSome decades following the Peal and Lambert study, supporting
\nevidence for a bilingual advantage in general cognitive functioning
\nfor children was found in studies using a variety of
\nexperimental paradigms. For example, Bialystok (1992) reported
\nthat bilingual children performed better than their monolingual
\ncounterparts on the Embedded Figures Test. In this test, participants
\nmust find a simple visual pattern concealed in a larger complex
\nfigure. Bialystok suggested that the better performance of
\nbilingual children might reflect their superior ability to focus
\non wanted information and ignore misleading information. That
\nis, the advantage might be one of enhanced selective attention,
\ninvolving the ability to inhibit irrelevant or unwanted information
\nand the complementary ability to concentrate on relevant aspects.
\nThis interpretation was in line with another demonstration in
\nwhich children were asked to judge whether phrases were grammatically
\ncorrect, regardless of meaning. Bilingual children were
\nbetter than their monolingual age-mates at ignoring the misleading
\nmeaning in sentences such as \u2018\u2018Apples grow on noses\u2019\u2019 or
\n\u2018\u2018Why is the cat barking so loudly\u2019\u2019 and stating that the grammar
\nwas correct (Bialystok, 1988). More generally, research
\ndemonstrated enhanced metalinguistic awareness in bilingual
\nchildren compared to their monolingual peers (Ben-Zeev, 1977;
\nCummins, 1978; Galambos & Hakuta, 1988; Ricciardelli, 1992)
\nWhy might bilingual children show an advantage in the
\nability to inhibit attending to unwanted information and select
\nrelevant aspects The answer may follow from the surprising
\nfinding described earlier: that when bilingual speakers use one
\nlanguage, the other language is still active. However, this does
\nnot mean that a full analysis of incoming stimuli in the nonused
\nlanguage inevitably takes place, nor that formulating speech in
\none language fully activates the relevant words and grammar of
\nthe other language. It seems rather that the second language is
\npotentially active, that some analysis is typically carried out,
\nand that more analysis takes place when combinations of
\ncontext and meaning increase the likelihood that words and
\nphrases from the nonused language are in fact relevant to the
\nspeaker\u2019s or listener\u2019s concerns.
\nThe idea that the nonrelevant language is always potentially
\nactive accounts for another observation on bilingual speakers:
\nthat they occasionally intrude words from the alternate
\nlanguage during speech. Though such intrusions are rare
\n(Poulisse, 1997; Poulisse & Bongaerts, 1994; Sandoval et al.,
\n2010), these instances reflect occasions in which the appropriate
\nword in the language being used is difficult to locate or the word
\nor phrase in the nonused language is made particularly likely
\nbecause of the context or its salience. Bialystok (2001) commented
\nthat such intrusions are more common in bilingual children
\nthan in adults and are also more common (anecdotally at least)
\nin older than in younger adults (Sandoval, 2010). In turn, this
\nage-related pattern suggests that the brain mechanisms responsible
\nfor maintaining attentional set (in this casemaintaining attention
\non the selected language) are less effective in childhood and
\nin older adulthood. One candidate for such mechanisms is integrity
\nof frontal lobe functioning, since it is well established that
\nthe frontal lobes develop slowly in childhood and are among the
\nfirst parts of the brain to decline in efficiency in older adulthood
\n(Craik & Grady, 2002; Diamond, 2002; Raz, 2000).
\nOur suggestion is that bilingual speakers must develop an
\nunusually strong ability to temporarily inhibit access to the
\nnonrelevant language while maintaining attentional set
\n(\u2018\u2018maintaining concentration\u2019\u2019) on the language in current use.
\nThis ability may be mediated by the frontal lobes and may
\ntherefore exhibit a lifespan developmental trend that peaks in
\nyoung adulthood. The further suggestion is that the constant
\nnecessity to exercise this inhibitory control leads to the
\ndevelopment of particularly effective attentional functions that
\nare then drawn on to mediate good performance on a variety of
\nnonverbal tasks requiring inhibition of unwanted or misleading
\nmaterial and concurrent selection of relevant aspects.
\nInhibition or selection
\nWhat would it mean to have enhanced control over attentional
\nfunctions When Bialystok (2001) surveyed studies of the
\neffects of bilingualism on children\u2019s cognitive processes,
\nshe concluded that \u2018\u2018the most consistent empirical finding
\nabout the cognition of bilingual children is their advantage in
\nselective attention and inhibition\u2019\u2019 (Bialystok, 2001, p. 246).
\nThis conclusion was based on some of her own work (e.g.,
\nBialystok, 1988, 1992) as well as on a growing number of
\nstudies from other laboratories. An example that illustrates how
\nthese processes are used by children is the dimensional change
\ncard sort task (DCCS) developed by Zelazo, Frye, and Rapus
\n(1996). This is a game in which images that vary on two dimensions,
\nusually shape and color, are sorted according to one of
\nthem. For example, cards containing either red or blue circles
\nor squares are sorted into containers marked by an image of
\neither a red square or a blue circle. Children are asked to first
\nsort the cards by one dimension\u2014blues in this box and reds
\nin this box\u2014and then to switch to the other\u2014circles in this box
\nand squares in this box. The dramatic finding is that young
\n98 Bialystok et al.
\n98
\nchildren can easily state the new rule but continue to sort by the
\nfirst rule; they have great difficulty overriding the habit set up
\nin the first phase. When this experiment was repeated with
\nbilingual and monolingual children aged between 4 and 5 years,
\nthe bilingual children were markedly better at switching to the
\nnew rule (Bialystok, 1999; Bialystok & Martin, 2004). This
\nresult was obtained despite there being no difference in
\npre-switch performance. The researchers thus concluded that
\nthe constant need to inhibit the nonused language generalized
\nto more effective inhibition of nonverbal information.
\nThese demonstrations were followed by studies that
\nextended the investigation to adults and used other paradigms
\nin which a prepotent response tendency must be inhibited. One
\nsuch situation is embodied in the Simon task. The participant
\nviews a screen on which either a red or green square appears;
\nthere are two response keys, one for red squares and the other
\nfor green squares. The keys are positioned below the sides of
\nthe screen, and the squares can appear either immediately
\nabove their relevant response key (congruent condition) or
\nabove the other key (incongruent condition). Response latencies
\nare longer in the incongruent case, and the difference
\nbetween incongruent and congruent latencies is termed the
\nSimon effect. If participants are able to resist the misleading
\ninformation carried by spatial position in the incongruent situation,
\nthe Simon effect will be smaller, and we may conclude
\nthat they have well-developed inhibitory control mechanisms.
\nUsing this logic, Bialystok, Craik, Klein, and Viswanathan
\n(2004) tested groups of younger and older adults who were
\neither monolingual or bilingual on a version of the Simon task.
\nWhen the colored squares are presented centrally, there is no
\nconflict between the position of the stimulus and side of the
\nappropriate response, and in this case there were no differences
\nin reaction time between monolinguals and bilinguals, although
\nolder participants took longer to respond (Fig. 3a). When the
\ncolored squares appeared laterally, however, Simon effects
\nwere found, and these were larger for monolinguals\u2014especially
\noldermonolinguals (Fig. 3b).This evidence for a bilingual advantage
\nin inhibitory control in adults extended the results of previous
\nstudies on children. Moreover, the bilingual advantage was
\nespecially strong in older adults, suggesting that bilingualism
\nmay afford some protection against at least some forms of
\ncognitive aging.
\nTwo other unexpected results emerged from this study. The
\nfirst is that the bilingual advantage in response time was found
\nfor congruent as well as incongruent stimuli. This result was
\nobtained in all three experiments and has been consistently
\nobserved in subsequent studies (e.g., Costa, Herna\u00b4ndez, &
\nSebastian-Galles, 2008). Why should there be a bilingual
\nadvantage for congruent stimuli when there is no misleading
\ninformation to inhibit Most experiments of this sort are run
\nunder mixed conditions in that experimental runs contain both
\ncongruent and incongruent stimuli, so participants must keep
\nthe rule in mind throughout the experimental run and monitor
\neach trial for the type of processing needed (conflict or no
\nconflict). It may be that bilinguals are also better at these
\naspects of executive control. The test of this conjecture is to
\ncheck what happens in experiments containing pure runs of all
\ncongruent or all incongruent stimuli, and the finding there is
\nthat the bilingual advantage disappears (Bialystok, Craik, &
\nRyan, 2006).
\nThe second unexpected result found by Bialystok et al.
\n(2004) was that prolonged practice on the Simon task reduced
\nthe difference between monolinguals and bilinguals.
\nIn Experiment 3, participants performed the Simon task for
\n10 consecutive blocks of 24 trials; by the end of the session the
\nmonolingual disadvantage had disappeared and both groups
\nshowed minimal differences between congruent and incongruent
\nstimuli. It is interesting to speculate that everyone may be
\nable to inhibit the effects of misleading information in specific
\nsituations with sufficient practice but that bilinguals can learn
\nthis type of inhibition more rapidly.
\nThe Stroop effect may be considered the \u2018\u2018gold standard\u2019\u2019 of
\ntests of inhibition. In this paradigm, participants name colors as
\nrapidly as possible, both when the colors are presented as
\ncolored squares on a screen and when the stimuli are color
\nnames (e.g., \u2018\u2018red,\u2019\u2019 \u2018\u2018green,\u2019\u2019 \u2018\u2018blue\u2019\u2019) but presented in a different
\ncolored font (e.g., the word \u2018\u2018red\u2019\u2019 printed in green ink). The
\ndifference in speed between naming colored squares and the
\ncolor of words is the Stroop effect; again, a smaller Stroop
\neffect indicates a strong ability to inhibit the misleading
\ntendency to name the word rather than its color. Bialystok
\net al. (2008a) tested groups of 24 younger and older adults who
\nwere monolingual or bilingual on this paradigm. In four different
\nconditions, participants named the color of displays of Xs,
\nnamed a color word presented in black font, named the font
\ncolor of words printed in their own color (congruent condition),
\nand named the font color of words printed in a different color
\n(the incongruent Stroop condition). For the control conditions
\n(naming words and colored Xs), naming times were faster for
\nwords and for younger participants but there were no
\nlanguage-group differences. Response times for the congruent
\nand incongruent colored-word conditions are shown in Figure 4
\nas differences (positive or negative) from the time taken to
\nname colored Xs. The figure shows that congruent stimuli are
\nassociated with relatively faster response times (a facilitation
\neffect) and are indicated by positive RT differences in the
\nfigure, whereas incongruent stimuli show the classic Stroop
\npattern in which slower response times are indicated by negative
\nRT differences. Statistical analysis revealed a significant
\nthree-way interaction of age, language, and congruence; both
\nyounger and older bilinguals sustained smaller costs than their
\nmonolingual peers, but only the older bilinguals showed greater
\nfacilitation. We may thus conclude that the older bilinguals
\nexhibited greater degrees of cognitive control than their monolingual
\ncounterparts, in that they both took greater advantage of
\ncongruent conditions and at the same time were less impaired
\nby incongruent conditions. Younger bilinguals showed the
\nlatter effect but not the former.
\nOther results from the Bialystok et al. (2008a) study
\nincluded a bilingual advantage for the older participants in a
\nversion of the Simon task using directional arrows, but no bilingual
\nadvantage for either age group in a condition in which
\nBilingual Minds 99
\n99
\nparticipants were instructed to respond in the direction opposite
\nto that indicated by a single arrow. There was also no bilingual
\nadvantage on the Sustained Attention to Response Task
\n(SART; Robertson, Manly, Andrade, Baddeley, & Yiend,
\n1997), which involves withholding a response to the number 3
\nwhile responding rapidly to all other digits. In both these latter
\ntasks, the participant can encode a simple rule (e.g., \u2018\u2018press in the
\nopposite direction\u2019\u2019) and then follow that rule; there is essentially
\nno need to select one aspect of the stimulus and suppress other
\naspects, as with the Simon, Stroop or flanker tasks. This account
\nclaiming no need for control in these tasks is reinforced by other
\nresults showing no bilingual advantage in children who were
\ninstructed to respond \u2018\u2018day\u2019\u2019 when shown a picture of a dark
\nnight, and \u2018\u2018night\u2019\u2019 when shown a sunny day (Martin-Rhee &
\nBialystok, 2008). These investigators also replicated the finding
\nof no bilingual advantage in children given the reverse arrow
\ntask, even though the same children demonstrated a bilingual
\nadvantage when the arrows were placed in side positions on the
\ndisplay that created conflict.
\nThis pattern of presence and absence of advantages is in line
\nwith the distinction between interference suppression and
\n0
\n150
\n300
\n450
\n600
\n750
\n900
\n1050
\n1200
\n1350
\n1500
\n(a) Control Condition
\n(b) Simon Effect
\n30-39 40-49 50-59 60-69 70-79
\nMean RT (ms)
\nAge
\n30-39 40-49 50-59 60-69 70-79
\nAge
\nMonolingual Bilingual
\n0
\n100
\n200
\n300
\n400
\n500
\n600
\n700
\n800
\n900
\n1000
\nRT Difference (ms)
\nFig. 3. Mean reaction time (RT) on Simon task by decade for monolinguals and bilinguals.
\nGraph a shows mean RT for the control condition; Graph b shows mean RT cost as the
\ndifference between congruent and incongruent trials (Simon effect). From Bialystok, Craik,
\nKlein, and Viswanathan (2004).
\n\u2013300
\n\u2013250
\n\u2013200
\n\u2013150
\n\u2013100
\n\u201350
\n0
\n50
\n100
\n150
\nType of Difference Score
\nMean RT (ms)
\nFacilitation Cost
\nYoung Mono
\nYoung Biling
\nOld Mono
\nOld Biling
\nFig. 4. Mean reaction time (RT) and standard error for
\nfacilitation and cost for young monolinguals and bilinguals
\nand older monolinguals and bilinguals in the Stroop task.
\nThe values are mean differences from baseline (0 milliseconds)
\ncalculated as the average difference in the time
\ntaken to name colors from the time taken to name neutral
\nstimuli (Xs). From Bialystok, Craik, and Luk (2008a).
\n100 Bialystok et al.
\n100
\nresponse inhibition proposed by Bunge, Hazeltine, Scanlon,
\nRosen, and Gabrieli (2002). Interference suppression refers to
\nsituations in which misleading information evokes a faulty
\nresponse and must therefore be ignored or suppressed; this
\nappears to be the type of situation that bilinguals can deal with
\nparticularly well. Response inhibition is the ability to avoid
\nresponding in error to a habitual or highly salient cue, and bilinguals
\nshow no advantage under these circumstances. In other
\nwords, the bilingual advantage appears when there is conflict
\nbetween two potential responses, but not when there is a need
\nto withhold a single primed response.
\nAs a final converging point, Kimberg, D\u2019Esposito, and
\nFarah (1997) have commented that patients with lesions in the
\nprefrontal cortex are impaired on tasks in which the most
\nsalient cue evokes the wrong response and must therefore be
\nsuppressed to select the cue associated with the correct
\nresponse. If one effect of bilingualism is to boost frontal lobe
\nfunctions, it follows that bilingual children and adults should
\nbe adept at tasks involving interference suppression.
\nConverging evidence from other studies has supported the
\nconclusion that bilinguals show strong abilities to inhibit irrelevant
\nor interfering information. Zied and colleagues (2004)
\nfound that balanced bilingual adults of various ages responded
\nmore rapidly than unbalanced bilinguals on the Stroop task. In
\nan ingenious series of studies, Philipp and colleagues (Philipp,
\nGade, & Koch, 2007; Philipp & Koch, 2009) asked participants
\nwho were fluent in three languages (English, French, &
\nGerman) to switch among their languages in a number naming
\ntask; thus \u2018\u20182\u2019\u2019 was named either \u2018\u2018two,\u2019\u2019 \u2018\u2018deux,\u2019\u2019 or \u2018\u2018zwei\u2019\u2019
\ndepending on a concurrent instruction. The main finding was
\nthat naming in language A was slower on the third trial of a
\nsequence ABA than in a sequence CBA. That is, A (e.g.,
\nFrench naming) was slower on the third trial of a sequence
\nFrench, German, French than it was in the third trial of a
\nsequence English, German, French, suggesting that in the first
\nsequence French was subjected to a temporary global inhibitory
\neffect to permit access to German. When French was
\nneeded immediately after that, negative priming slowed access
\nto the target name. Although there is no bilingual advantage in
\nthis study\u2014monolinguals were not tested, and the study was
\nnot designed to test for bilingual advantages\u2014the results
\ndemonstrate the role of a general inhibitory process applied
\nto the nonused language in order to avoid interference effects
\nin the selected language.
\nNegative priming was also used in an experiment by
\nTreccani, Argyri, Sorace, and Della Sala (2009). Targets could
\nappear at one of four positions on a screen and participants
\nresponded by pressing one of four keys. When a target was
\naccompanied by a distractor stimulus in another location,
\nbilingual adults were better able to ignore it (interference
\nsuppression) and so made fewer errors than did theirmonolingual
\ncounterparts. However, the bilinguals were more negatively
\naffected (making more errors than monolinguals) when a target
\nappeared in the position previously occupied by a distractor item.
\nIn this situation, the better inhibition of the distractor carried over
\nto the next trial, providingmore negative priming to the bilingual
\nparticipants. The authors concluded that whether bilinguals show
\nan advantage or a disadvantage relative to monolinguals depends
\non task characteristics.
\nThe studies reviewed so far have endorsed the notion that the
\nbilingual advantage found in these studies is due to an advantage
\nin inhibition or suppression of interfering material, but there
\nremains the possibility that bilinguals show an advantage in the
\npositive selection of wanted information. The latter interpretation
\nis favored by a number of investigators. Costa, Miozzo, and
\nCaramazza (1999) argue that although lexical candidates in both
\nlanguages are active during the planning of an utterance, the
\nintention to speak in one language rather than another effectively
\nrestricts selection to words in the target language. Colzato and
\ncolleagues (Colzato et al., 2008) set out to compare what they
\ntermed \u2018\u2018active inhibition\u2019\u2019 with \u2018\u2018reactive inhibition.\u2019\u2019 By active
\ninhibition they mean general global suppression of the nonrelevant
\nlanguage (cf. inhibition in the study by Philipp & Koch,
\n2009) and by reactive inhibition they mean lack of suppression
\nof specific interfering stimuli. Evidence for the latter was found
\nin the attentional blink paradigm in which detection of a target
\nstimulus is impaired if the same stimulus was presented earlier
\nin a rapid sequence of events. The authors predicted that if bilinguals
\nshow more reactive inhibition, then they will process the
\nfirst presentation of the target to a greater extent and therefore
\nshow less suppression of intervening items. Without suppression,
\nthese items would then interfere more with the second
\npresentation of the target, creating a larger attentional blink
\neffect. This is what they found, and so they suggested that the
\nbilingual advantage is not due to constant exercise of inhibition
\nof the nonused language but rather to prolonged practice at
\nmaintaining the relevant attentional set, though they grant that
\nsuch selection may involve strong inhibition of competing items.
\nThe debate over inhibition versus selection may rest on a
\nfalse dichotomy: Inhibition may not be an all-or-none phenomenon
\nbut may rather be found to different degrees under some
\ncircumstances. One such factor that might influence the degree
\nof inhibition required to perform a task is the effect of context.
\nKroll, Bobb, Misra, and Guo (2008) describe work showing
\nthat cross-language cognates were activated (that is, naming
\na word in one language activated its cognate in bilinguals\u2019
\nsecond language) when a word was named out of context, but
\nthis cognate facilitation was eliminated in contexts that were
\nsemantically constrained in that the required word was more
\nclearly determined from the context (see also Schwartz &
\nKroll, 2006; van Hell & de Groot, 2008). One possibility, then,
\nis that the degree to which both languages are active may not be
\nconstant but may vary probabilistically with the contextual
\nconstraints provided by language, topic (sample nursing essay examples by the best nursing assignment writing service), and the external
\nenvironment.
\nAnother possible effect of context was suggested by Costa,
\nHerna\u00b4ndez, Costa-Faidella, and Sebastian-Galles (2009). They
\ntested monolinguals and bilinguals on versions of a flanker task
\nin which different conditions contained varying proportions of
\nincongruent trials: 8%, 25%, 50%, or 92% (therefore mixed with
\n92%, 75%, 50%, or 8% congruent trials, respectively). The bilingual
\nadvantage was strongly present in the 50%\/50% version,
\nBilingual Minds 101
\n101
\nreduced in the 75%\/25% version, and entirely absent in the 92%\/
\n8% version. The authors conclude that the bilingual advantage is
\nrelated to their greater ability to monitor the environment when
\nthe probability of change is high, as in the 50%\/50% condition.
\nUnder low-monitoring conditions, when most of the trials are of
\none type, there is little need to monitor and thus no bilingual
\nadvantage is found. The notion of monitoring is similar to the
\nidea of set maintenance described previously by Colzato et al.
\n(2008). Costa and his colleagues also make the interesting prediction
\nthat bilinguals who live in situations in which their two
\nlanguages are used in different contexts (e.g., Italian at home,
\nEnglish at work) rarely need to monitor language changes and
\nso may not develop strong monitoring abilities and thus show
\nno bilingual advantage.
\nFinally, the distinction between selection and inhibition was
\nexamined in a study by Herna\u00b4ndez, Costa, Fuentes, Vivas, and
\nSebastian-Galle\u00b4s (2010), in which participants rapidly judged
\nhow many items (letters or numerals) appeared on a screen. The
\nitems appeared either in a congruent form (1, 22, 333), an incongruent
\nform in which the displayed numerals did not match the
\nrequired response (e.g. 3, 11, 222), or a neutral form (Z, GGG,
\nMM). Relative to the neutral baseline, congruent stimuli were
\nassociated with faster response times (facilitation) and incongruent
\nstimuli with slower response times (interference). Bilingual
\nparticipants showed smaller interference effects but larger facilitation
\neffects than their monolingual counterparts (cf. Bialystok,
\nCraik, & Luk, 2008a), so their advantage may be described as
\none of better executive control of perception\/action processing.
\nThe conclusion of Costa and colleagues is that the bilingual
\nadvantage is reasonably high level, involving top-down working
\nmemory processes, and is manifested as enhanced set maintenance
\nor monitoring. This description suggests that the advantage
\nmay stem from enhanced frontal lobe effectiveness, as
\nsuggested by Bialystok (2001).
\nSelective attention and executive control
\nWe have seen in the previous section that research aimed at
\nassessing inhibitory abilities in bilinguals evolved to consider
\nsuch concepts as selection, set maintenance, and monitoring.
\nHowever, the distinction between these concepts and notions
\nof attention and executive control is difficult to discern.
\nIn many ways, all these concepts are simply aspects of attention
\nand executive control. Therefore, in this section we consider
\nwork that assesses group differences in attention and control
\nmore directly.
\nCosta et al., (2008) examined the performance of monolingual
\nand bilingual participants on the attentional network task
\n(ANT) developed by Fan, McCandliss, Sommer, Raz, and
\nPosner (2002). The bilinguals were young adults who spoke
\nCatalan and Spanish; the monolinguals were young adults who
\nspoke Spanish only. The ANT task assesses abilities on three
\ndifferent attentional networks: alerting, orienting, and executive
\ncontrol. The test is a flanker task in which the participant
\nresponds to the direction of a central arrow that is flanked by
\ntwo arrows on each side pointing in the same (congruent) or
\ndifferent (incongruent) direction as the central target arrow.
\nAlerting is studied by presenting a cue before the target stimulus,
\nand orienting is assessed by the presence or absence of a
\ncue signaling the future spatial position of the target. The
\nresults supported the hypothesis of greater attentional control
\nby bilinguals in the alerting and executive control networks.
\nThe bilingual participants responded faster than themonolinguals
\non all conditions and showed a smaller cost for the incongruent
\ntrials, indicating better conflict resolution. Two final results from
\nthis study were that this bilingual advantage disappeared by the
\nthird block of trials (cf. Bialystok et al., 2004, Study 3) and that
\nbilinguals had smaller switching costs between congruent and
\nincongruent trials, a point to which we will return.
\nSimilar results were obtained by Carlson and Meltzoff
\n(2008) with much younger participants. They administered a
\nbattery of executive function tests to 50 kindergarten children
\nwho were English-speaking monolinguals, English-Spanish
\nbilinguals, or children who were in a language immersion elementary
\nschool. The major finding was that the native bilingual
\nchildren performed better on the executive function battery
\nthan did both other groups, once differences in age, vocabulary,
\nand parents\u2019 education and income levels were statistically
\ncontrolled (recent work extends this finding that bilingualism
\ncan offset the negative effects of lower socioeconomic status
\non task switching to young adults; Prior & Gollan, 2010).
\nThe effects were specific to only some aspects of control: There
\nwere no bilingual advantages in suppressing a motor response
\non delay-of-gratification tasks (response inhibition) but
\nsignificant advantages on conditions requiring memory and
\ninhibition of attention to a prepotent response (interference
\nsuppression; cf. Martin-Rhee & Bialystok, 2008). The authors
\nconclude by endorsing the notion that \u2018\u2018language experiences
\ncan influence further development of frontal lobe functions such
\nas inhibition and the control of attention\u2019\u2019 (p. 293).
\nTask switching
\nThe features of executive control discussed to this point
\nare somewhat invisible in ordinary cognitive performance.
\nThe interference suppression that allows us to perform a Stroop
\ntask or ignore misleading flankers in the ANT seems to have
\nlittle role in everyday cognition. A more noticeable aspect of
\nexecutive control might be task switching\u2014the ability to move
\neasily between two tasks, keeping two protocols simultaneously
\nactive. Task switching might come closest to the special
\nprocesses bilinguals engage in as they switch between
\nlanguages.
\nIn one of the first studies to find positive things to say about
\nbilingualism, Peal and Lambert (1962) suggested, as we noted
\nearlier, that bilingual children may show an advantage in mental
\nflexibility\u2014an idea presumably stemming from the fact that
\nbilinguals must switch easily from one language to another. A
\nlarge body of research investigates task switching, typically by
\nasking participants to classify a long series of two-dimensional
\nstimuli by one criterion or the other as rapidly as possible. Such
\nsorting times are relatively short when successive trials
\n102 Bialystok et al.
\n102
\ncontinue with the same criterion (e.g., continue sorting by
\nshape), but local switching costs are incurred when instructions
\nchange to sort by the other dimension (e.g., switch and sort by
\ncolor). Some runs of trials involve only one dimension (e.g., all
\ntrials require sorting by color), so it is also possible to measure
\nmixing costs, defined as the difference in time taken to classify
\na set of trials under single- and dual-criterion conditions
\n(Meiran & Gotler, 2001; Pashler, 2000). Typically, sorting
\ntimes are longer when it is necessary to bear in mind the
\nrequirement to switch when the instruction changes.
\nSeveral studies have now explored monolingual\u2014bilingual
\ndifferences in such paradigms, with the prediction that
\nbilinguals should show reduced costs, owing perhaps to their
\nprolonged practice in switching languages and monitoring
\nwhich language may be spoken in which context. The
\nprediction with regard to which type of cost might be affected
\nby bilingualism is less clear. To take an analogous
\ndifference between individuals\u2014development and aging over
\nthe lifespan\u2014the typical finding is that younger adults have
\nsmaller mixing costs than children or older adults do, whereas
\nthe age groups do not differ markedly on local switch cost
\n(Reimers & Maylor, 2005; for review, see Mayr & Liebscher,
\n2001). The relatively large value for mixing costs in young
\nchildren and older adults was speculatively attributed to their
\ngreater difficulty in simultaneously maintaining two task sets.
\nGiven bilinguals\u2019 apparent advantage in maintaining task set
\n(Colzato et al., 2008), it should follow that they should also
\nshow reduced mixing costs. This result was indeed reported
\nby Bialystok et al. (2006) in an experiment in which participants
\nneeded to respond on the same or opposite side as a target
\ndepending on a cue. Participants performed single-task runs in
\nwhich only one cue was used and mixed runs in which either
\ncue might appear. Response times to the target were slower
\nunder mixed conditions, and mixing costs were greater for
\nmonolingual participants.
\nThree other task-switching studies investigating monolingual
\nand bilingual college students have yielded mixed results.
\nFirst, Prior and MacWhinney (2010) asked participants to classify
\nstimuli by color (red\/green) or shape (circle\/triangle). They
\nfound no mixing-cost advantage to bilinguals and no speed
\ndifferences between the two groups on non-switch trials, but
\nthe bilinguals were faster than monolinguals on switch trials
\nwhen instructions changed to sort on the alternate dimension.
\nThus, their study found a local switch-cost advantage to bilinguals
\nwith no mixing-cost advantage. Subsequent experiments
\nreplicated the switching advantage in bilinguals who reported
\nthat they frequently switched languages and no switching advantage
\nin a less balanced group, although this less-balanced group
\nexhibited significant associations between fluency in a nondominant
\nlanguage and switching and mixing costs (Prior & Gollan,
\n2010). These results suggest dissociations of switching and
\nmixing costs with respect to group differences and imply that
\nmultiple aspects of bilingualism may influence task shifting.
\nFrequent language switching may lead to task-switching advantages,
\nwhereas close monitoring of which language may be
\nspoken when (and avoiding switching) may lead to taskmixing
\nadvantages. A third study provides clues with respect
\nto the origin of the mixing advantage. In this study, Herna\u00b4ndez,
\nMartin, Barcelo, and Costa (2010) also used a color\u2013shape
\nswitching task to test young adult Spanish-Catalan bilinguals
\nand Spanish-speaking monolinguals. A rule was set at the beginning
\nof a run (e.g., classify by shape), then trials continued for an
\nunpredictable number without further cues until a second cue
\nwas presented. The second cue was either explicit (e.g.,
\nclassify by color) or implicit (e.g., switch to the other rule or
\nrepeat the previous rule). It was found that switching was slower
\nthan repeating the same criterion but that this effect did not
\ninteract with group. Implicit cues were associated with slower
\nresponse times thanwere explicit cues, and this effect did interact
\nwith language group; bilinguals were faster in the implicit version
\nbut not in the explicit version. The researchers also measured
\n\u2018\u2018restart costs\u2019\u2019\u2014slower RTs for the first trial than for the second
\ntrial after a repeat cue. Bilinguals had smaller costs thanmonolinguals
\non thismeasure too, but again only with implicit cues.These
\nresults suggest that the bilingual participants were better at maintaining
\nthe current set, monitoring the changing situation, and
\nupdating when necessary. Although the task was similar in many
\nrespects to that used by Prior and MacWhinney, the instructions
\nwere presented differently, and the bilinguals\u2019 use of two very
\nsimilar languages might account for the differences in results.
\nIf that is the case, one would need to be cautious about generalizing
\nabout differences in local and global task switching between
\nmonolinguals and bilinguals without considering further details
\nof the participants and task situation.
\nThere are still too few studies to conclude much that is
\ndefinitive on the effect of bilingualism on task switching.
\nBetter bilingual performance for mixing costs (Bialystok
\net al., 2006) and dealing with implicit cues (Herna\u00b4ndez et al.,
\n2010) suggests that the advantage is in monitoring or set maintenance,
\nbut the results of the Prior and MacWhinney (2010)
\nstudy speak more to the notion of greater mental flexibility
\nor greater inhibitory control. In addition, bilingual language use
\nmay require different underlying control processes and may
\ntherefore lead to different processing advantages (Prior &
\nGollan, 2010). The few current studies involve many differences
\nin methods and in participants, so the traditional cry of
\n\u2018\u2018more research is needed!\u2019\u2019 is very much the case before
\ndecisive conclusions can be drawn.
\nBilingualism and memory
\nSince being bilingual necessarily entails the management and
\nappropriate development of two language systems, it makes
\nsense that these special skills of mental management should
\nalso apply to aspects of attention, conflict resolution, and
\ncognitive control. But should bilingualism confer benefits on
\nother cognitive functions\u2014on memory, for example The
\nanswer may depend substantially on the type of memory being
\ninvestigated. Working memory (the manipulation of small
\namounts ofmaterial held briefly inmind) is generally considered
\nto be either part of, or closely related to, executive processes, so
\nbilingual advantages might be expected with such paradigms.
\nBilingual Minds 103
\n103
\nHowever, performance on semanticmemory tasks (tapping stores
\nof acquired knowledge) is likely to reflect experience with the
\ntype of information tested. Given that we have seen that bilingual
\nvocabulary levels are typically lower than those of comparable
\nmonolinguals, we might expect that retrieval of verbal information
\nwould be poorer in bilingual participants, and, as described
\nin the first section, performance on naming tasks and other tasks
\nof lexical retrieval do in fact show this pattern. Moreover, performance
\non episodicmemory tasks may again depend on the material
\nin question.
\nFor both working memory and episodic memory, the
\nevidence is mixed. In one condition of the Simon task reported
\nby Bialystok et al. (2004), color patches were presented centrally
\nand so required no cognitive control, and participants
\nresponded to the color by pressing one of two response keys.
\nIn one version, two possible colors mapped to the two keys, and
\nin the second version, four possible colors mapped to the two
\nkeys, with two colors associated with each key. The four-color
\nversion has greater demands on working memory, so working
\nmemory costs were taken as the difference between the
\ntwo-color and the four-color versions. Bilingual participants
\naged 30 to 80 years showed smaller costs than did their monolingual
\ncounterparts, and were therefore deemed to show a bilingual
\nadvantage in working memory. This advantage has
\nobvious similarities to the bilingual advantage in mixing costs
\nfound in some studies using the task-switching paradigm.
\nThe results of other studies are less clear. Bialystok, Craik,
\nand Luk (2008a) gave older and younger adult bilinguals and
\nmonolinguals two tests of working memory. The self-ordered
\npointing task requires participants to remember which of 12
\nabstract drawings have been selected previously; no
\nlanguage-group differences were found. The Corsi Block task
\nis a test of short-term spatial memory, and in this case there was
\na bilingual advantage for younger but not older adults. Feng
\n(2008) also presented various working memory tasks to monolingual
\nand bilingual children and young adults. In the latter
\ngroup, she found no bilingual advantage in either the Corsi
\nBlock task or in alpha span\u2014a word-span task in which participants
\nmust mentally rearrange a short list of words from a
\npresented order into alphabetic order. However, Feng did find
\na bilingual advantage for both children (Feng, Diamond, &
\nBialystok, 2007) and adults (Feng, 2008) in a test of spatial
\nworking memory in which items are presented in a random
\norder in a 3 3 matrix (for children) or on a 5 5 matrix (for
\nadults). The task is to recall the positions of the items in
\n\u2018\u2018matrix order\u2019\u2019\u2014that is, starting at the top left and progressing
\nthrough the matrix left to right, line by line.
\nWhether or not there is a bilingual advantage in working
\nmemory may depend on the type of material used and the way
\nin which working memory is tested. Working memory tasks
\nmay not be tapping one fixed cognitive mechanism but rather
\nreflect a family of related functions generally concerned with
\nholding and manipulating material that is in the focus of attention
\n(Cowan, 1999) or simply \u2018\u2018held in mind.\u2019\u2019 Tentatively, it
\nseems to us that a bilingual advantage should be found in working
\nmemory, given the previously reviewed evidence
\nsuggesting that bilinguals have an advantage in set maintenance
\n(e.g., Colzato et al., 2008) and in the related abilities
\nof monitoring (Costa et al., 2009) and updating (Herna\u00b4ndez
\net al., 2010).
\nThe effects of bilingualism on episodic memory are also
\nunclear at present, as only a few studies have been reported.
\nIn the studies described earlier, Fernandes, Craik, Bialystok,
\nand Kreuger (2007) found poorer word recall by bilinguals, but
\nWodniecka et al. (2010) reported that the disadvantage was
\novercome when monitoring the list was required, as in the
\nassessment of recollection. At present, therefore, there is little
\nclear evidence for a bilingual advantage in episodic memory,
\nsome tentative suggestions of an advantage in working memory,
\nand a clear disadvantage for bilinguals in the retrieval of
\nitems from semantic memory.
\nThe bilingual advantage across the lifespan
\nDoes the bilingual advantage in cognitive control change
\nthrough the lifespan It is well established that executive control
\nfunctions first increase in effectiveness from childhood to
\nyoung adulthood and then decline in the course of aging (Craik
\n& Bialystok, 2006; Dempster, 1992; Diamond, 2002), so it
\nseems possible that bilingualism might modify such functions
\nand that the bilingual advantage might also show the same
\nlifespan trajectory.
\nIf the bilingual advantage in cognitive performance we have
\nseen in this section is related to the enhancement of the
\nexecutive control function, how early might we expect these
\ndifferences to emerge given that the executive function system
\nis late to develop Similarly, if the cognitive advantage
\ndepends on protracted experience with two languages in which
\nattention to systems and switching between them becomes
\npracticed, could such advantages be found in children before
\nthey use language productively A recent study by Kovacs and
\nMehler (2009b) provides dramatic evidence for the very early
\nappearance of a bilingual advantage in 7-month-old infants.
\nThe infants who participated in the experiments were preverbal
\nbut were classified as bilingual if they had been exposed to two
\nlanguages from birth because one parent consistently spoke to
\nthem in one language and the other parent used a different
\nlanguage. The researchers reported three experiments in which
\nthe infants learned to look for a visually rewarding puppet at
\none of two squares on a screen in response to either a speech
\nstimulus (a trisyllabic nonsense word) or a visual pattern. After
\nthe learning phase, which was performed equally well by
\nmonolingual and bilingual infants, a new cue signaled the
\nappearance of the visual reward in the alternate square. Thus,
\ninfants had to inhibit their first learned response and switch
\nto a new response. The finding in all three experiments was that
\nthe bilingual infants learned to switch to the other square but
\nthe monolingual infants did not. The authors suggest that simply
\nperceiving and processing utterances from the two languages
\nduring the first few months of life serves to accelerate
\nthe development of general executive functions that can then
\nbe applied in a variety of cognitive situations. This interesting
\n104 Bialystok et al.
\n104
\nresult does not negate the notion that some forms of the
\nbilingual advantage are caused by inhibition of the nonused
\nlanguage but rather raises the interesting possibility that the
\nadvantage may have more than one causative mechanism.
\nWhat happens throughout life once bilingualism has
\nmodified these executive control systems Does the bilingual
\nadvantage simply increase as the person accumulates
\nexperience dealing with two or more languages And if
\nbilingualism offers some protection against age-related cognitive
\ndecline (Bialystok, Craik, & Freedman, 2007; Kave\u00b4, Eyal,
\nShorek, & Cohen-Mansfield, 2008), does an increase in the
\nbilingual advantage occur simply as a result of monolinguals
\nshowing a steeper decline in cognitive functioning than
\nbilinguals do
\nOne problem with assessing these possibilities is that most
\nstudies deal with just one age group, so the opportunity to make
\nlifespan developmental comparisons is limited. One exception
\nis an article by Bialystok, Martin, and Viswanathan (2005)
\nreporting studies on 5-year-olds and young, middle-aged, and
\nolder adults performing the same task, the Simon task. This
\nseries of studies showed a bilingual advantage (faster RTs) that
\nwas substantial in the 5-year-old children, virtually absent in
\n20-year-old undergraduate participants, but present again in
\ngroups of middle-aged (30\u201359) and older (60\u201380) adults. The
\nauthors suggested that the absence of an advantage in young
\nadults may reflect the fact that cognitive control is most
\nefficient at that time, so bilingualism provides no further boost.
\nThe two studies involving middle-aged and older adults were
\nconsistent in showing a larger bilingual advantage for the
\noldest (60\u201380) group, because the drop in efficiency from the
\nmiddle-aged to older participants was greater for monolinguals
\nthan for bilinguals. This pattern of an especially strong
\nadvantage for the oldest bilingual participants was also found
\nin three other studies by Bialystok and collaborators (Bialystok
\net al., 2004, 2006, 2008a; see Fig. 3b).
\nIn the first two sections of this report, we reviewed
\nbehavioral studies of language and cognition, presenting the
\ngeneral finding that bilingual children and adults have smaller
\nvocabularies and slower lexical access times than do their
\nmonolingual peers but that they also show enhanced cognitive
\ncontrol on a variety of tasks. What are the neural correlates of
\nthese effects Is it possible to detect these subtle differences
\nthrough neuroimaging techniques In the next section, we
\nsurvey the current evidence for structural and functional
\nchanges in the brain that result from bilingual experience.
\n3. Neural Bases of Language Control in
\nBilinguals
\nWhether one speaks just one language or more than one
\nlanguage, everyday use of language involves cognitive control.
\nBilingual speakers do not develop a separate control system;
\nrather, as we have argued above, the use of two languages
\nimposes on a single control system additional demands beyond
\nthose experienced by speakers of just one language. Our central
\nclaim is that this control system or network is used by both
\nmonolinguals and bilinguals but that the additional role in
\nbilingual language processing modifies it, changing its performance
\nfor all tasks. In Section 2 we examined the cognitive
\nconsequences of such enhanced control. Here we make explicit
\nthe components of the network involved in language control,
\ndemonstrate how they also mediate the cognitive advantages
\nshown by bilinguals, and explore the neural bases of control
\nusing many of the same tasks discussed in Section 2.
\nFigure 5 identifies the basic components of the control
\nnetwork, distinguishing it from the bilingual language system
\nthat it controls. We can think of the bilingual speaker as performing
\nmultiple language tasks such as speaking one language rather
\nthan another. A bilingual must also monitor the language in use
\nand either maintain it if the circumstance demands (e.g., when
\nspeaking to a monolingual speaker of that language)\u2014and so
\navoid inadvertently switching into the other language\u2014or, on
\noccasion, deliberately switch to the other language if the circumstance
\nchanges\u2014for example, when a monolingual speaker of
\nthe other language enters the conversation.
\nThe task-switching paradigm described in Section 2 can be
\nadapted to test language switching in bilinguals, and we use it
\nhere to illustrate the workings of the network for language control.
\nThe task is to name a presented numeral, for instance 4,
\nin L1 (e.g., French) or in L2 (e.g., English). The participant\u2019s
\nselection of one task rather than another governs the output
\nfrom the bilingual language system; if the task is to \u2018\u2018name in
\nFrench,\u2019\u2019 the person says \u2018\u2018quatre.\u2019\u2019 To be successful, the
\nactivation of the selected task (i.e., the mental representation
\nCognitive Control Network
\nExecutive
\nprocess
\nMonitoring
\nprocess
\nCompeting task
\nschemas
\nBilingual
\nlanguage
\nsystem
\nFig. 5. Basic components of the cognitive control network
\nfor bilinguals, distinguishing it from the bilingual language system
\nthat it controls. The bilingual language system refers to
\na person\u2019s mental representation of their languages; for
\npresent purposes, we leave this undifferentiated and focus
\non the components of the control system. A bilingual can
\nperform different language tasks: He or she can choose to
\nspeak one language rather than another, can switch between
\nlanguages, or can translate between them. Task schemas
\nconfigure the bilingual language system so as to achieve the
\nintended task, but these schemas are in competition to control
\nthe bilingual language system. Their activation must be
\nmonitored and, if necessary, adjusted by a higher-order
\nexecutive process. For example, a bilingual must either
\nmaintain the current language in use if the circumstance
\ndemands (e.g., when speaking to a monolingual speaker of
\nthat language)\u2014and so avoid inadvertently switching into
\nthe other language\u2014or, on occasion, deliberately switch
\nto the other language if the circumstance changes\u2014for
\nexample, when a monolingual speaker of the other language
\nenters the conversation.
\nBilingual Minds 105
\n105
\nof the task set, its \u2018\u2018task schema\u2019\u2019) must exceed and continue to
\nexceed that of the competing task. Therefore, the speaker must
\nmonitor the speech output, and where marked slowing is
\ndetected or an error is noticed (i.e., saying \u2018\u2018four\u2019\u2019 rather than
\n\u2018\u2018quatre\u2019\u2019) the speaker must make some adjustments. The
\nspeaker might increase the activation of the required task
\n(\u2018\u2018name in French\u2019\u2019) or suppress the activation of the alternative
\ntask (\u2018\u2018name in English\u2019\u2019)\u2014as discussed Section 2 when we
\nexamined selection versus inhibition. Executive and monitoring
\nprocesses are needed to establish new schemas (e.g., in the
\ncase of an experimental task) and invoke ones that are already
\npart of a person\u2019s repertoire. In this role, these processes work
\nproactively; in response to performance difficulties, they work
\nreactively (Green, 1998). A person may be conscious of the
\nneed to make such adjustments when an overt error is made, but
\non other occasions control adjustment may occur automatically,
\nas in the way a thermostat adjusts power output in
\nresponse to a deviation from the desired temperature (Green,
\n1998; Paradis, 2009; see Fernandez-Duque & Knight, 2008, for
\nwork suggesting that only conscious control leads to performance
\nbenefits across tasks).
\nWhat produces slower responses or overt naming errors
\nMarked slowing in naming in French, for example, may reflect
\nsuccessful inhibition of a strongly competing name in the other
\nlanguage (i.e., English), whereas naming in the wrong language
\nindicates a failure of control. Activation of the English name
\nmay also increase the activation of the task schema for English
\nand lead to increased competition with the task schema for
\nFrench. Resolving such competition requires suppression of the
\nEnglish task schema. In other words, when a bilingual speaks
\ntwo languages regularly, speaking in just one of these
\nlanguages requires use of the control network to limit interference
\nfrom the other language and to ensure the continued
\ndominance of the intended language.
\nWould there be a difference in the switch cost if the bilingual
\nwere more fluent in French (L1) than in English (L2) In that
\ncase, French would be the easier task and English the more
\ndifficult task, and the interesting finding is that it takes longer
\nto switch into the easier task (143 milliseconds, ms) than it does
\nto switch into the more difficult task (85 ms; Meuter & Allport,
\n1999). A plausible explanation for this seemingly paradoxical
\nasymmetry of switch costs is that in order to name in English (the
\nmore difficult task), the easier task (naming in French) must be
\nstrongly inhibited, and it takes more time to reinstate the easier
\ntask, producing an asymmetry in the switching cost. Similar
\nresults were obtained in a study by Misra, Guo, Bobb, and Kroll
\n(2007). Participants were asked to name pictures in L1 or L2
\nunder either mixed conditions, when either L1 or L2 could be
\nrequired, or in blocked conditions, when only one language was
\nused. Their results showed that naming in L1 was slower under
\nmixed conditions than it was under blocked conditions and that
\nL1 naming was slower than L2 naming in the mixed conditions
\n(an effect of reversed language dominance), supporting the
\ninterpretation that L1 was inhibited to permit the possibility of
\nL2 naming. No asymmetry of switch costs is found when
\nbilinguals switch languages voluntarily, yet a complete reversal
\nof language dominance is found\u2014again suggesting some form
\nof inhibition of the L1 (Gollan & Ferriera, 2009).
\nNot all the research is consistent on this point. Finkbeiner,
\nAlmeida, Janssen, and Caramazza (2006) had bilingual
\nparticipants name digits in either L1 or L2 and then perform
\na picture-naming task in their dominant language. Following
\nthe argument for greater inhibition of the dominant language,
\nthe hypothesis is that it should take longer to name pictures
\nin L1 if the digit naming had been performed in L2. However,
\nFinkbeiner et al. found no difference in picture-naming latency
\nand so concluded that no inhibition of the nonused language
\ntook place. Their conclusion, though, is difficult to reconcile
\nwith evidence of global language inhibition identified in the
\nlater study by Philipp and Koch (2009). A more complete
\nreview of these issues is presented by Kroll et al. (2006).
\nThe experimental research on bilingual task switching
\ngenerally uses explicit cues to signal the language required
\non the current trial. Deliberate language switching in real life
\nalso requires a speaker to monitor the context for cues as to
\nwhich language to speak (e.g., this person speaks L1 but not
\nL2) and ensure correct language selection and suppression of
\nany competing responses. Our premise, then, is that the additional
\ndemands on bilingual speakers relative to monolingual
\nspeakers entail greater use of this control network. The particular
\ntasks that are subject to control are varied (e.g., naming
\npictures in one language, describing a scene in a second
\nlanguage, translating from one language to another). However,
\nthe components involved in monitoring performance and
\nensuring correct selection of the intended language task are
\napplicable to other nonlanguage tasks, and, as we saw in the
\nprevious section, they appear to generalize to nonverbal tasks.
\nNeural bases of cognitive control
\nFigure 6 identifies the cortical and subcortical structures that
\nare components of the cognitive control network in Figure 5.
\nWe follow others in separating the neural structures mediating
\ncontrol from those that process linguistic or other kinds of sensory
\nor motor data (Posner & Petersen, 1990). The idea is that
\nthese cortical and subcortical structures work together to limit
\nthe effects of interference and to switch between tasks.
\nFor example, they may function as a control loop that continually
\nmonitors attention to the required task (e.g., Botvinick,
\nBraver, Barch, Carter, & Cohen, 2001; Kerns et al., 2004).
\nIn its monitoring role, the anterior cingulate cortex may detect
\nand help resolve interference (Lau, Rogers, & Passingham,
\n2006) and signal the prefrontal cortex, with its widespread
\nconnections to other regions (Dehaene & Changeux, 1991;
\nDesimone & Duncan, 1995; Miller & Cohen, 2001), to alter the
\nactivation of the task schemas. Another region in the medial
\nfrontal cortex superior to the anterior cingulate cortex, the presupplementary
\nmotor area (pre-SMA), is also implicated in the
\ncontrol of action but seems linked more closely to spontaneously
\nchosen actions than to response conflict (Lau et al., 2006).
\nThe parietal cortex is involved in representing the task,
\nthrough its connection to the prefrontal cortex, and in selecting
\n106 Bialystok et al.
\n106
\namong competing responses, through its connection to the
\nbasal ganglia (Bunge et al., 2002). The basal ganglia are particularly
\nimportant in task switching. Whereas traditional
\nviews (Alexander & Crutcher, 1990; Mink, 1996) emphasize
\nthe role of the basal ganglia in the control of movement,
\nrecent work emphasizes their key role in cognitive control too
\n(e.g., Graybiel, 2000; Kotz, Schwartze & Schmidt-Kassow,
\n2009). Both cortical and subcortical structures are therefore
\nimportant in understanding how interference is controlled and
\ntask switching achieved, so it is necessary to understand their
\nrole in language control. We shall examine the involvement of
\nthese regions in two broad categories of tasks: those requiring
\nthe control of interference and those based on switching
\nbetween tasks and languages.
\nThe control of interference
\nUsing neuroimaging studies, we now consider the neural bases
\nfor controlling interference. These studies mostly rely on functional
\nmagnetic resonance imaging (fMRI) to assess the response
\nof different neural structures when there is an increased demand
\nto control interference. The basic data are the relative activation
\nof different neural regions as detected by fMRI. A common
\nassumption is that an increase in activation reflects an increase
\nin difficulty. There is more extensive research on the control
\nof interference in monolingual speakers, so our review makes
\nuse of meta-analyses of data from a number of studies.
\nInterference control in monolinguals. The argument being
\ndeveloped here is that bilinguals use the cognitive control
\nnetwork shown in Figure 6 to control interference from the
\ncompeting language. Therefore, it is necessary to establish that
\nthese regions are recruited when monolinguals perform tasks
\ninvolving response conflict. We consider work that has looked
\nat the neural regions involved in controlling interference in
\nthree different tasks that, as described in Section 2, show a
\nbilingual advantage: a nonverbal flanker task, a Simon task,
\nand a Stroop task.
\nAlthough studies have examined these tasks separately, the
\nstrongest evidence for a common set of regions involved in
\ncognitive control comes from studies testing two or more of
\nthem in the same individuals (Fan, Flombaum, McCandliss,
\nThomas, & Posner, 2003; Liu, Banich, Jacobson & Tanabe,
\n2004; Peterson et al., 2002). Fan et al. (2003) contrasted performance
\non a flanker task, a Simon task, and a manual version of
\nthe Stroop task in which individuals pressed one of four buttons
\ncorresponding to the font color of a presented word. In all the
\ntasks, individuals responded faster in congruent trials than in
\nincongruent trials. Fan et al. identified two regions that showed
\na common effect of conflict: one in the anterior cingulate cortex
\nand one in the left prefrontal cortex (see Roberts & Hall,
\n2008, for a review).
\nNee, Wager, and Jonides (2007) examined data from
\n47 papers using different interference tasks. Their review confirmed
\nthe importance of the left prefrontal cortex (dorsolateral
\nAnterior Cingulate Cortex
\n\u2022 Attention
\n\u2022 Conflict monitoring
\n\u2022 Error detection
\nInferior Parietal Lobule
\n\u2022 Maintenance of
\nRepresentations
\n\u2022 Working memory
\nBasal Ganglia, Caudate
\n\u2022Language selection
\n\u2022 Set switching
\n\u2022 Language planning
\n\u2022 Lexical selection
\n\u2022 Executive functions
\n\u2022 Decision-making
\n\u2022 Response selection
\n\u2022 Response inhibition
\n\u2022 Working memory
\nPrefrontal Cortex
\nFig. 6. Principal brain structures involved in cognitive control, and their putative functions. From Abutalebi and
\nGreen (2007).
\nBilingual Minds 107
\n107
\nregion) and the anterior cingulate cortex, along with a region in
\nthe left posterior parietal cortex, in overcoming Stroop conflict.
\nNeuropsychological data also support the importance of a
\nfrontal region in verbal control. Hamilton and Martin (2005)
\nfound that a patient with damage to a left inferior frontal region
\nshowed a large interference effect in the Stroop task but
\ninterference within the normal range for a spatial-conflict task.
\nThe analyses of Nee et al. also showed that different kinds of
\nconflict induce slightly different patterns of neural response.
\nIn resolving conflict based on resisting responding to an
\ninfrequent stimulus, frontal and parietal regions in the right
\nhemisphere, in addition to the left dorsolateral prefrontal cortex
\nand the anterior cingulate cortex, were activated.
\nMuch research on the control of interference has examined
\nthe role of cortical structures but ignored the role of subcortical
\nstructures, such as the caudate, that, as indicated in Figure 6,
\nshould be involved in selecting among competing responses.
\nHowever, there is some relevant research on these subcortical
\nstructures. The left head of the caudate activates when a previously
\nlearned movement has to be inhibited (Shadmeher &
\nHolcomb, 1999; Parsons, Harrington, & Rao, 2005) and when
\na prepotent response has to be blocked (Li, Yan, Sinha, & Lee,
\n2008). The caudate is also active in controlling interference in
\nthe Stroop task (Ali, Green, Kherif, Devlin, & Price, 2010). A
\nreasonable supposition, then, is that the caudate is involved in
\nthe inhibition of plans of action and therefore controls both verbal
\nand nonverbal types of interference.
\nTo summarize, neuroimaging research with monolinguals
\nconfirms that a network involving the prefrontal cortex,
\nanterior cingulate cortex, and caudate is recruited in tasks that
\nrequire resolution of conflict from competing responses.
\nInterference control in bilinguals. We argue that bilinguals
\nuse this same network to control conflict from two languages.
\nTherefore, if retrieving the name of a picture is effortful for
\nbilinguals because of the need to overcome interference from
\nthe other language, then we would expect to find evidence for
\nthe involvement of this control network in a picture naming
\ntask. De Bleser et al. (2003) examined covert picture naming
\nin an L1 and a later-acquired L2. (For technical reasons,
\nneuroimaging studies sometimes adopt the expedient of asking
\nparticipants to mouth picture names or to name pictures only
\ncovertly, so they will not move.) Participants were native
\nspeakers of Flemish\/Dutch who had learned French from the
\nage of 10. In one condition the picture names were cognates
\n(i.e., the translation equivalents were phonological and
\northographically similar), and in another condition they were
\nnoncognates. For pictures with noncognate names, naming in
\nthe L2 showed more activation in regions responsible for linking
\nconceptual information and word form than did naming in
\nthe L1. The more important result is that activation increased in
\ntwo inferior frontal regions associated with more effortful lexical
\nand semantic retrieval. Therefore, data from this study,
\nalong with others (e.g., Abutalebi, Cappa, & Perani, 2001;
\nRodriguez-Fornells et al., 2005), suggest that naming in the
\nL2 is associated with more effortful processing, an idea
\nconsistent with the involvement of cognitive control processes.
\nMoreover, as proficiency in the L2 increases, the relative
\ndifference in activation between L1 and L2 decreases, again
\nconsistent with the idea that there is a decrease in effort
\n(Abutalebi & Green, 2007).
\nEven early and highly proficient bilingual speakers show
\nevidence of more effortful processing in their L2 and recruitment
\nof control regions, despite demonstrating a processing
\nprofile that is similar to that of native speakers. Kovelman,
\nBaker, and Petitto (2008) asked Spanish-English bilinguals and
\nEnglish monolingual speakers to judge whether visually presented
\nsentences were plausible or not. For the bilinguals, the
\nsentences were presented in separate experimental blocks for
\neach language. The English sentences (and their Spanish
\ntranslations) varied in their syntactic complexity, being either
\nsubject\u2013object relatives (e.g., \u2018\u2018The child spilled the juice that
\nstained the carpet\u2019\u2019) or arguably more complex object\u2013subject
\nrelatives (e.g., \u2018\u2018The juice that the child spilled stained the carpet\u2019\u2019).
\nAs expected, bilingual speakers showed a differential
\nresponse to complexity as a function of the presented language.
\nSpanish relies more on morphological marking than
\nword order to signal grammatical relations. Like the English
\nmonolinguals, bilingual speakers showed increased left inferior
\nfrontal activation for the more complex English sentences.
\nIn contrast, they showed no differentiation as a function of
\ncomplexity when processing the Spanish sentences. However,
\nthe study also showed that bilingual speakers processing
\nEnglish showed more activation in the left frontal region than
\nmonolingual English speakers did. In other words, processing
\neven in a language in which they are highly fluent is more
\neffortful for bilingual speakers and engages regions associated
\nwith cognitive control.
\nIncreased proficiency in the L2 may also alter processing in
\nthe L1 precisely because of increased competition. In reading,
\nthe mappings between letters and sounds differ between languages,
\nso the same string of letters can give rise to conflicting
\npronunciations. For example, what happens when native readers
\nof Italian (which has a regular relationship between letters
\nand sounds) read in their L1 after learning English, in which the
\nrelationship is irregular As vocabulary knowledge in English
\nincreases, native Italian readers reading Italian show a linear
\nincrease in activation in a left frontal region associated with
\nmapping letters to sounds (Nosarti, Mechelli, Green, & Price,
\n2010). Such an outcome indicates increased competition. More
\nto the point, there is a linear increase in activation in a left
\nfrontal region used to resolve irregular pronunciations in
\nmonolingual native English readers. Interestingly, this region
\nis also one that helps resolve lexical competition (e.g., de
\nZubicaray, McMahon, Eastburn, & Pringle, 2006). These data
\nagain suggest that bilingual speakers and readers, at least in
\ncontexts where both languages are active, experience increased
\nverbal conflict and recruit a left frontal region to resolve it.
\nOther research allows us to see both cortical and subcortical
\nregions involved in controlling interference. Van Heuven,
\nSchriefers, Dijkstra, and Hagoort (2008) made use of a special
\nrelationship that exists between words in two languages such as
\n108 Bialystok et al.
\n108
\nEnglish and Dutch. Their participants were highly proficient
\nDutch-English university students who had learned English at
\nthe age of 10 to 12 years. Van Heuven et al. asked participants
\nto decide whether a presented word was a real English word or
\nnot\u2014an English lexical decision task. Some English words,
\ntermed interlingual homographs, are also real words in Dutch;
\nfor example, room means \u2018\u2018cream\u2019\u2019 in Dutch. In an English lexical
\ndecision task, \u2018\u2018room\u2019\u2019 elicits a competing \u2018\u2018No\u2019\u2019 response
\nbecause it is a word in Dutch, and in an English lexical decision
\ntask Dutch words should receive a \u2018\u2018No\u2019\u2019 response. Relative to
\ncontrol words, therefore, correctly deciding that an interlingual
\nhomograph was a real English word elicited increased
\nactivation in three regions displayed in Figure 6: the left inferior
\nprefrontal regions, the anterior cingulate cortex (together
\nwith another region we have noted previously in the medial
\nfrontal cortex, the pre-SMA) and the left caudate. As expected,
\nvan Heuven et al. observed no differential activation for
\ninterlingual homographs in a group of monolingual English
\nspeakers. This experiment left unresolved whether the
\nactivated regions were signaling conflict arising from the
\nstimulus itself (i.e., \u2018\u2018room\u2019\u2019 elicits two meanings in Dutch-
\nEnglish bilinguals) or conflict arising from ambiguities associated
\nwith the response (i.e., is \u2018\u2018room\u2019\u2019 a word in English).
\nTo determine which regions responded to stimulus-based
\nrather than response-based conflict, the researchers performed
\nanother experiment on a separate group of bilinguals
\nfrom the same population. In this case, participants knew that
\nsome of the words might be Dutch words and responded
\n\u2018\u2018Yes\u2019\u2019 to each real English word regardless of whether it was
\nalso a Dutch word. In this case, interlingual homographs
\nelicited increased activation only in left prefrontal regions,
\nsuggesting that the left prefrontal regions are sensitive to
\nstimulus-based conflict. In contrast, the response profile of
\nthe anterior cingulate cortex (and the pre-SMA) and left caudate
\nreveals regions that are either sensitive to, or help
\nresolve, response-based conflict.
\nThe precise impact of the other language might depend on
\nhow active it is. It is reasonable to expect that it will be most
\nactive when it is being used at the same time when bilinguals
\nare in what Grosjean (1998) termed a bilingual mode and they
\nare switching between languages. We consider the response of
\nthe control regions in the section on language switching.
\nTask switching
\nThe second paradigm within which to examine the neural
\nbases of cognitive control is task switching. Different types
\nof data can help identify the structures recruited in switching
\nbetween languages or between other types of tasks. Stroke
\ndamage to a specific structure can lead to difficulties in task
\nperformance and so provide evidence of its causal role in cognitive
\ncontrol that complements the data from neuroimaging
\nstudies. Again, we begin by establishing the neural basis of
\ntask switching in monolinguals and then compare those patterns
\nto data from bilinguals performing task switching and
\nlanguage switching.
\nTask switching in monolingual speakers. The occurrence of
\na stroke is a tragic and dramatic event that helps to explicate the
\nrole of regions in Figure 6 for task switching. Greater damage
\nto the left frontal cortex leads to increases in switch costs and so
\nreflects difficulty in holding the current task in mind or in
\nselecting the correct response, although inhibition of inappropriate
\ntasks or associated responses might be more closely
\nlinked to the right frontal cortex (Aron, Monsell, Sahakian, &
\nRobbins, 2004). The anterior cingulate cortex is less susceptible
\nto stroke, but it is sometimes necessary to ablate part of it
\nsurgically. Postoperatively, such patients have difficulty
\nresponding to a cue that requires them to switch the direction
\nin which they move a joystick (Williams, Bush, Rauch,
\nCosgrove, & Eskandar, 2004). Damage to the basal ganglia
\nalso severely impairs a person\u2019s ability to switch between tasks
\nand to overcome the interference from the prior task. We illustrate
\nwith a nonverbal task (Yehene, Meiran, & Soroker, 2008).
\nYehene et al. asked their patients to press one of two keys in
\nresponse to the position of a target schematic face in a 2 2
\nmatrix on the basis of one of two rules. In the top-down task
\nthey had to press Key 1 if the target was in the top half of the
\ngrid and Key 2 if it was in the bottom half. In the left\u2013right task
\nthey pressed Key 1 if it was on the left side of the grid and Key
\n2 if it was on the right. The rule was cued on each trial. On critical
\ntrials, the correct response depended on the application of
\nthe correct rule, because Key 1 designated a target that was up
\nor left and Key 2 designated a target on the bottom or right.
\nTherefore, if a target was in the upper right cell of the grid,
\npressing Key 1 was correct for the top-down task but Key 2 was
\ncorrect for the left-right task. Basal ganglia patients were
\nseverely impaired when the rule switched in this task, signaling
\nthe importance of that structure in such tasks.
\nIn a meta-analysis of data from neuroimaging studies involving
\ndifferent types of task switches (e.g., rule switching, changes
\nin target locations, and different response sets), Wager, Jonides,
\nand Reading (2004) confirmed that the regions in Figure 6 are
\nreliably activated on task-switch trials. The prefrontal cortex is
\nsensitive to changes in demands involved in switching between
\ntasks (Christoff & Gabrieli, 2000; MacDonald, Cohen, Stenger,
\n& Carter, 2000) with more complex working memory demands
\nassociated with right frontal activation (Simmonds, Pekar, &
\nMostofsky, 2008). The anterior cingulate cortex is sensitive to
\nchanges in tasks and to errors consistentwith its role inmonitoring
\nand in adaptive control in response to errors (e.g., Hyafil,
\nSummerfield,&Koechlin, 2009). Parietal areas are also involved
\nin remapping stimuli to response according the new task (e.g.,
\nCorbetta & Shulman, 2002; Dosenbach et al., 2006). Finally, the
\nbasal ganglia play a role in shifting response. In a study in which
\nparticipants tracked a continuous sine wave by controlling a
\ncursor, activation increased in the left caudate when the current
\ntrial required a movement opposite to that used previously
\n(Lungu, Binenstock, Pline, Yeaton, & Carey, 2007).
\nLanguage switching in bilinguals. In monolingual participants,
\nthe regions identified in Figure 6 were shown to contribute to
\ntask switching. Do they also contribute to language switching
\nBilingual Minds 109
\n109
\nand interfere with linguistic behavior in bilingual patients
\nPatient reports indicate that damage to the prefrontal cortex,
\ninferior parietal cortex, or basal ganglia structures affect the
\nability of bilingual patients to voluntarily switch from one
\nlanguage to another. As the anterior cingulate cortex is less
\nsusceptible to stroke, there are fewer reports for this structure,
\nbut all the other regions indicated in this control network
\nshow a clear role in language switching. Damage to either the
\nleft prefrontal lobe (Stengel & Zelmanowitz, 1933; Zatorre,
\n1989; Fabbro, Skrap, & Aglioti, 2000) or left inferior parietal
\nlobe (Herschmann & Po\u00a8tzl, 1920; Po\u00a8tzl, 1925, 1930; Leischner,
\n1948\/1983) can yield pathological switching, that is, unintended
\nor inappropriate switching between languages. Lesions to the
\nhead of the caudate elicit either selective recovery of the current
\nlanguage, as if it is no longer possible to disengage fromit (Aglioti
\n& Fabbro, 1993; Aglioti, Beltramello, Girardi, & Fabbro, 1996),
\nor pathological switching between languages (Abutalebi,
\nMiozzo, & Cappa, 2000; Marie\u00a8n, Abutalebi, Engelborghs, &
\nDe Deyn, 2005). In the case reported by Abutalebi et al., A.H.,
\na trilingual speaker of Armenian (L1), English (L2), and Italian
\n(L3), was unable to avoid switching languages when naming
\nsimple pictures. For example, although he named the picture of
\na clock correctly in Armenian in an Armenian testing session,
\nhe named it in Italian in theEnglish naming session and inEnglish
\nin the Italian naming session.
\nThat the circuits underlying language switching are
\nwidespread is also indicated by data from transient cortical and
\nsubcortical electrical stimulation of the brain during surgery for
\ntreating glioma tumors or epileptic foci when the patient is
\nawake. In the case of bilingual speakers, this stimulation can
\nlead to involuntary switching from naming pictures in one
\nlanguage to naming them in another, reflecting the temporary
\ndisruption of control (Moritz-Gasser & Duffau, 2009a, b).
\nNeuroimaging studies of bilinguals without brain damage
\nprovide complementary data. In a study with early Spanish-
\nEnglish bilingual speakers, Hernandez et al. (2000) reported
\nmore activation in left dorsolateral prefrontal cortex when
\nswitching between naming pictures in English and Spanish
\nthan when naming pictures in just one language (see also
\nHernandez, 2009; Hernandez, Dapretto, & Bookheimer,
\n2001; Chee, Soon, & Ling Lee, 2003). Price, Green, and von
\nStudnitz (1999) used single words and found that switching
\nbetween languages increased activation in regions associated
\nwith phonological processing (a left inferior frontal region,
\nBroca\u2019s area, and parietal cortices). Taken together, these data
\nindicate that language switching or mixing induce increased
\nfrontal and parietal activity consistent with the requirement
\nto inhibit ongoing activity associated with one task and select
\na relevant response in the face of competition.
\nMore recent research provides a fuller picture of the control
\nregions involved in language switching. Abutalebi and
\ncolleagues (2008) studied German-French bilinguals who
\nlearned French relatively late (around 12 years of age) and were
\nenrolled in a translation course. The task was to name pictures
\nin their L1 under one of two conditions. In the single-language
\ncondition, a cue signaled whether they were to name the picture
\n(e.g., \u2018\u2018cup\u2019\u2019) or generate an associated verb (e.g., \u2018\u2018drink\u2019\u2019). In
\nthe dual-language condition, the cue signaled whether they
\nwere to name the picture in their L1 or in their L2. In this dual
\ncondition, the nontarget language is very active. The key
\nanalysis is the contrast between naming a picture in L1 in the
\nsingle-language condition and naming it in L1 in the
\ndual-language condition. Abutalebi et al. found that naming
\npictures in the dual-language condition induced more extensive
\nactivation in the left prefrontal cortex, the anterior cingulate
\ncortex, and the left caudate nucleus than did naming the
\nsame pictures in the single-language condition. Furthermore,
\nthe study confirmed more extensive activation in these regions
\nwhen individuals were using their weaker L2. These results are
\nstrong support for the importance of these regions in selecting
\na language in the face of interference.
\nOther studies have used neuroimaging to examine the neural
\nbasis of the asymmetric cost in switching between a language
\nin which one is more proficient and a language in which one
\nis less proficient (Meuter & Allport, 1999). We illustrate this
\nwith a functional imaging study, but there is other work using
\nevoked reaction potentials that is consistent with the idea that
\nswitching between languages involves a process of actively
\ninhibiting the other language (Jackson, Swainson, Cunnington,
\n& Jackson, 2001) even if that does not invariably lead to an
\nasymmetry in switching cost (e.g., Christoffels, Firk, &
\nSchiller, 2007; Verhoef, Roelofs, & Chwilla, 2009, 2010).
\nWang, Xue, Chen, Xue, and Dong (2007) examined the cost
\nof switching into L1 (Chinese) versus a newly acquired L2
\n(English). In line with the view presented here that the same
\nregions are used for cognitive control and language control,
\nWang et al. reported increased activation in the regions associated
\nwith control when subjects switched into L2. The pattern
\nagain is consistent with the idea that bilinguals must inhibit
\ntheir L1 to speak in their L2 when they are switching between
\nthe two languages. The persisting suppression delays naming
\ntime when individuals switch back into L1.
\nThe effects of language switching have also been examined
\nin comprehension, and, surprisingly perhaps, there is also good
\nevidence for the involvement of control processes. Language
\nswitching elicits a left caudate response in late bilinguals
\n(German-English\/Japanese-English) when they make semantic
\ndecisions about the meanings of words (Crinion et al., 2006).
\nThe left caudate is also activated when bilinguals encounter a
\nlanguage switch while listening to a narrative and make no
\novert response at such a juncture (Abutalebi et al., 2007). The
\nparticipants in this study were Italian-French bilinguals who
\nhad acquired French before the age of three and were living
\nat the time of testing in an Italian community in Geneva, where
\nFrench predominates. Switching elicited bilateral inferior frontal
\nactivity (along with activation in a language area). Most
\ninterestingly, a switch into the less-exposed language (Italian)
\nelicited activation of the left caudate and the anterior cingulate
\ncortex. Such a neural response indicates the need to distinguish
\nbetween the processes responsible for implementing control
\nfrom processes associated with overcoming the effects of such
\ncontrol. In the present case, switching into the less dominant
\n110 Bialystok et al.
\n110
\nlanguage in a comprehension task appears to demand more
\nneural resources to overcome (suppress) the activation of the
\nmore exposed (dominant) language. In a production task, such
\na neural response may give rise, as we have seen, to slower
\nnaming when switching back into the more dominant language
\nin order to overcome its earlier suppression.
\nFinally, a special type of language switching occurs when
\nbilinguals translate from one language to another, and this task
\nalso involves the cortical and subcortical structures depicted in
\nFigure 6. Price et al. (1999) reported that, in contrast to reading
\nin different languages, translating activated mainly the anterior
\ncingulate cortex and bilateral subcortical structures including
\nthe head of caudate. In that study, if participants did not know
\nthe translation equivalent they responded \u2018\u2018No\u2019\u2019 or \u2018\u2018Nein.\u2019\u2019
\nHowever, in other studies, left inferior frontal activation was
\nfound when that option was not available, both in singleword
\ntasks (Klein, Milner, Zatorre, Meyer, & Evans, 1995) and
\nin auditorily presented text translation by simultaneous interpreters
\n(Rinne et al., 2000). Further, Rinne et al. (2000)
\nreported that, since translation into the nonnative language is
\nthe more difficult task, left dorsolateral activation was more
\nextensive when the interpreters translated into their nonnative
\nlanguage. The involvement of subcortical structures along with
\nactivity in the left prefrontal cortex is also reported (Lehtonen
\net al., 2005). Lehtonen and colleagues studied Finnish-
\nNorwegian bilinguals who had learned Norwegian as adults
\n(21\u201336 years). Participants completed a translation task and a
\ncontrol task. In the translation task, they silently translated
\nvisually presented Finnish sentences into Norwegian and then
\ndecided whether a presented Norwegian probe sentence was a
\ncorrect translation of the Finnish sentence. In the control task,
\nthey silently read a Finnish sentence and determined whether a
\nFinnish probe sentence was identical to it. The contrast between
\nthe translation and control task yielded substantial activation in
\nthe left (ventrolateral) prefrontal cortex and in a region of the
\nbasal ganglia (globus pallidus) that is activated in suppressing
\ncompeting responses (Atallah, Frank, & O\u2019Reilly, 2004; Ali
\net al., in press). Taken together, these data provide evidence for
\nthe involvement of the cortical and subcortical regions of the
\ncontrol network in a task special to bilinguals.
\nLocal switching and mixing costs in bilingual and
\nmonolingual performance. The difference between local
\nswitch costs and mixing costs was discussed in Section 2, with
\nmost studies reporting smaller mixing costs for bilinguals and
\nwith more varied evidence for local switch costs. This distinction
\ncan also be examined using evidence from neuroimaging.
\nFrom a control point of view, these two types of cost are
\ninteresting because local switch costs reflect transient control
\nprocesses whereas mixing costs reflect the need for sustained
\ncontrol. In task-mixed blocks, individuals need to keep two
\ntasks active and monitor the world for cues as to which one
\nto perform.
\nDosenbach et al. (2006) provide a detailed analysis of the
\nregions involved in initiating a new task, sustaining it over a
\nsequence of trials, and responding to error. They argue that
\nthe anterior cingulate cortex, together with another
\nbilateral frontal region (the anterior insula\/frontal operculum)
\nform a core region for implementing and sustaining a
\nnew task. As yet, there are no comparable analyses for language
\nswitching in bilinguals, so we illustrate with evidence
\nfrom two studies that compare local switching and mixing
\ncosts in language tasks.
\nBraver, Reynolds, and Donaldson (2003) asked participants
\nto classify words according to whether they referred to objects
\nthat were natural versus created or whether the objects referred
\nto were large versus small. Participants carried out these tasks
\neither in separate blocks of trials or mixed in the same block of
\ntrials. The anterior cingulate cortex and prefrontal regions of
\nthe right hemisphere were activated in the mixed blocks but
\nshowed no variation with local switching. In contrast, local
\nswitching was accompanied by activation in left prefrontal and
\nparietal regions.
\nWang, Kuhl, Chen, and Dong (2009) extended these ideas to
\nlanguage switching. Native speakers of Chinese who started
\nlearning English around 12 years and who rated themselves
\nas being of low to moderate proficiency in English named
\ndigits silently either in single-language or mixed-language
\nblocks. Language of response was signaled by a verbal cue
\npresented 400 ms before the stimulus digit. Consistent with
\nprevious research (e.g., Meuter & Allport, 1999), it took longer
\nto switch back into Chinese than to switch into English (43 ms
\nvs. 8 ms.). There was also a mixing cost that was similar for
\nChinese and English (but see Christoffels, Firk, & Schiller,
\n2007; Kroll et al., 2006, for data showing that an L1 can reveal
\ngreater mixing costs). Importantly, however, local switching
\nand mixing costs were associated with different brain regions.
\nFor mixing costs, there was activation in bilateral prefrontal
\nand frontal regions. Unlike other studies, Wang and colleagues
\nreported no differential activation of the anterior cingulate
\ncortex, a difference they attribute to the more automatic retrieval
\nof numeral names. In contrast, and in line with the data of
\nBraver and colleagues (2003), local switch costs activated left
\nfrontal regions (along with other cortical and subcortical
\nregions). Based on an analysis of individual data, Wang and
\ncolleagues also proposed that a left parietal region plays a role
\nin overcoming inhibition or in reactivating the previous
\nlanguage.
\nBilingualism and the neural networks for control
\nWe have summarized research showing the neural regions
\ninvolved when individuals control interference in using one
\nof their languages and the regions involved when they switch
\nbetween languages. In both cases, the set of regions depicted
\nin Figure 6 is activated. These data suggest extensive overlap
\nwith the regions mediating cognitive control when monolingual
\nspeakers resolve interference or switch between different
\ntasks. Such a correspondence supports the proposal that the
\nbilingual advantage in nonverbal interference tasks and in task
\nswitching arises from their use of neural regions recruited in
\nlanguage control.
\nBilingual Minds 111
\n111
\nWe have relied on commonalities in the response of the
\ncontrol regions in bilingual and monolingual speakers faced
\nwith different tasks, but there may be subtle differences that are
\nmissed in such comparisons. It is important to have studies that
\ndirectly compare bilingual and monolingual speakers (matched
\non confounding variables such as IQ and socioeconomic class)
\nperforming the same nonverbal conflict or switching task. One
\nsuch study has identified differences between bilinguals and
\nmonolinguals (Bialystok, Craik, et al., 2005). The researchers
\ncontrasted two groups of early bilinguals (French-English and
\nCantonese-English) with a monolingual English group
\nperforming a Simon task. Bialystok and colleagues used
\nmagnetoencephalography (MEG) to identify the neural basis
\nof processing differences between the language groups and analyzed
\ntwo bands of signals: one associated with attentional control
\n(theta band) and the other associated with signal processing
\n(alpha band). The data indicated that there is a common network
\nused by all participants but with with subtle differences in how
\ninterference is controlled. Faster responding in the bilingual
\ngroups was associated with more activation in the signalprocessing
\nband in two left frontal regions and the left anterior
\ncingulate cortex, as distinct from the left middle frontal region
\nassociated with faster responding in monolingual speakers. It
\nwill be important to extend such research to other tasks.
\nWhy, then, might bilinguals, at least those who use both
\nlanguages on a regular basis and who acquired them early in
\nlife, show an advantage in overcoming interference and in task
\nswitching The position that we have sought to establish is that
\nit is due to the need to control linguistic interference with the
\ncorresponding demands to monitor and adapt behavior. Such
\ncontrol is required when individuals speak two languages.
\nIt may also be required when individuals use two sign languages
\nbut appears not to be important when individuals speak
\none language and sign in another. Consistent with this view,
\nEmmorey, Luk, Pyers, and Bialystok (2008) found that
\nspeech-sign bilinguals responded comparably to monolinguals
\nand did not show the advantage demonstrated by a group of
\nspeech-speech bilinguals on a flanker task; and Kovelman
\net al. (2009) confirmed that bilinguals who spoke one language
\nand signed another showed no increase in prefrontal activation
\nwhen they switched between the two, although they did show
\nincreased activation in language regions associated with
\nmapping meaning to form.
\nAs noted earlier,whether the source of the bilingual advantage
\nis the voluntary or the involuntary nature of control is an
\nopen question, though it may prove to be the former (cf.
\nFernandez-Duque&Knight, 2008).But given that there is such
\nan advantage, the control network in bilinguals may be more
\nefficient overall, or bilingualsmay adopt a more effective strategy
\nin performing nonverbal tasks. For example, in interference
\ntasks they might be better at maintaining the task goal
\nand so reduce the impact of conflicting information. In task
\nswitching, they may respond more efficiently to a task cue and
\nretrieve task goals more effectively. If this is the case, switching
\ncosts and demand on transient control processes would be
\nreduced. Longitudinal studies will be important here, because
\nit is known that older adults shift from a control strategy that is
\nproactive and maintains task-relevant goals to one that is reactive
\nand retrieves relevant information only when required
\n(Jimura & Braver, 2010; Paxton, Barch, Racine, & Braver,
\n2008). The bilingual advantage shown in older adults may
\nreflect their continued use of a proactive control strategy
\nsupported perhaps by left frontal structures and the anterior
\ncingulate cortex.
\nBilingual experience may also alter the capacity of the
\ncontrol network by altering the density of grey matter (i.e.,
\nthe nerve cell bodies together with axons and dendrites) in one
\nor more control regions (e.g., anterior cingulate cortex;
\ncaudate). It may even affect the white matter connections
\n(i.e., the myelinated axons that connect regions of grey matter).
\nPrior research indicates that cognitive, linguistic, and motor
\nabilities can correlate with differences in brain structure,
\n(e.g., Crinion et al., 2009; Draganski & May, 2008; Gaser &
\nSchlaug, 2003; Lee et al., 2007; Maguire et al., 2000; Mechelli
\net al., 2004). If one or two regions show marked differences
\nthen this would constrain accounts of the neural basis of the
\nbilingual advantage. Longitudinal studies are important, as
\nthey can rule out preexisting individual differences rather than
\nbilingual experience as the source of the difference. In this
\ncontext, studies of the aging brain (see Section 2) may prove
\nparticularly revealing, because age-related declines can be
\nrelated to changes in specific brain structures. Our supposition
\nis that deteriorating performance found in nonverbal-conflict
\ntasks will also be found in tasks involving language control.
\n4. Implications of Bilingualism for Clinical
\nPractice
\nThe behavioral studies reviewed in Sections 1 and 2 reveal a
\nnumber of differences between bilinguals and monolinguals
\nin a variety of cognitive domains. These differences have
\nproven to be useful for understanding the implications of
\nbilingualism for cognitive development and cognitive aging.
\nMoreover, the recent work in neuroimaging and related fields
\ndescribed in Section 3 is beginning to elucidate the neural
\ncorrelates that underlie proficient language use. The question
\nposed in the present section is whether these findings can be
\napplied to help practitioners in the areas of neuropsychology,
\neducational psychology, and speech\/language pathology deal
\nwith the problems of bilingual clients and patients.
\nThe challenge to professionals in these applied fields is that
\nbilingual individuals vary enormously in their language skills.
\nA few of the many factors that affect the degree of language
\nproficiency in bilinguals are age and manner of acquisition of
\neach language, degree of use of each language over a lifetime,
\nand literacy and level of formal education in each language.
\nIt seems likely that these same factors will also affect the extent
\nto which bilingualism modifies cognitive processing mechanisms.
\nIt is difficult to obtain a comprehensive assessment of all
\nrelevant factors in each individual case\u2014yet such assessment is
\nnecessary to interpret test performance accurately. This uncertainty
\nabout the details of individual bilingualism combined
\n112 Bialystok et al.
\n112
\nwith the lack of tests developed specifically for use with bilinguals,
\nthe lack of knowledge about how bilingualism affects
\nperformance on standardized tests that were developed for
\nmonolinguals, and the strong emphasis on language-based
\nassessment in clinical settings makes it difficult to answer some
\nof the most common referral questions about bilinguals.
\nTo simplify the following discussion, we assume that the
\nbilingual individuals had early exposure to two languages and
\nthat English is the dominant language spoken by the majority of
\npeople in the environment. However, much of the discussion
\nwould apply equally well to proficient bilinguals who acquired
\none of their languages late in life, to bilinguals who live in
\nbilingual communities in which one language is not clearly
\nin the majority, and certainly to situations in which English
\nis not the majority language.
\nThree general themes are common when bilingual individuals
\nare referred to a clinician for intervention or therapy.
\nAlthough the specific questions differ, these same themes are
\nevident for children, adults, and aging bilinguals. The first
\ntheme is to establish whether there is a cognitive impairment
\nor language impairment. In children, this question often
\ntakes the form of asking whether the child is learning English
\n(the second language) as quickly as she or he should be, and
\nif not, if there is a language impairment or more general
\ndevelopmental delay. For adults the concern is often linked
\nto test results. As we saw in Section 1, tests of verbal fluency
\nand naming generally reveal lower scores for bilinguals than
\nfor monolinguals, and these verbal scores are frequently lower
\nthan indicators of verbal memory or nonverbal functioning for
\nbilinguals. In a clinical setting, this pattern raises the concern
\nabout the possibility of brain injury or developmental impairment\u2014
\nprecisely what those tests were designed to diagnose\u2014
\nrather than the history of bilingual language use. For
\nboth children and adults, if language impairment is identified,
\nthere are inevitably questions about the best strategy for
\naccommodating the impairment and for facilitating communication
\nand recovery. For example, should treatment be provided
\nin just one or in both languages Would it be best to
\ntry to use primarily one language to ease the load on the compromised
\ncognitive system by avoiding bilingualism (e.g., by
\nswitching to using only the majority language at home)
\nA second theme is the need for advice on the best way to
\npromote rapid acquisition of English as the person\u2019s second
\nlanguage. For children the question is frequently framed in
\nterms of educational options: Is total immersion in English best,
\nor is it better to encourage parallel development of both
\nlanguages by including both as part of the academic curriculum
\nIn young adults, the concern is centered more on academic
\nachievement, and questions attempt to determine the role of
\nbilingual language use in academic outcomes. In middle-aged
\nand older adults, the focus again shifts to learning the language.
\nSome individuals are concerned about the length of time it is reasonable
\nto live in a country without learning the environmental
\nlanguage.
\nThe third theme is more specialized. Clinical intervention is
\nsometimes sought to assess the adequacy of English
\nproficiency for a specific purpose, such as functioning in
\nschool or in a professional setting. Adequate proficiency is also
\nessential for safety and security, as in understanding the conversation
\nin a medical interaction or discussing the risks of a
\nmedical procedure. Linguistic levels that may be perfectly adequate
\nfor some purposes may fail to support the ability to
\nunderstand complex information for which careful thought and
\ncautious decision making are required. These situations may
\nalso require the services of a clinician.
\nThere are a number of reviews on cognitive and language
\nassessment of bilinguals that provide useful information on the
\nchallenges that arise, on the kinds of questions to ask in clinical
\nsettings to obtain the necessary information to interpret
\nbilingual performance on language-based tests, and on how
\nbilingualism can affect performance on specific tests (e.g.,
\nAltarriba & Heredia, 2008; Baker, 2000; Cummins, 2000;
\nKohnert, 2007; Paradis, 2008; Paradis & Libben, 1987; Pen\u02dca
\n& Bedore, 2009; Ponto\u00b4n & Leo\u00b4n-Carrion, 2001; Rivera-Mindt
\net al., 2008; Valde\u00b4s & Figueroa, 1994). Here we attempt to
\nconnect questions about assessment of bilinguals more specifically
\nwith the experimental literature reviewed above.
\nBefore considering how bilinguals differ from monolinguals
\nin their performance on neuropsychological tests, it is helpful
\nto review what typically happens during a cognitive assessment.
\nNeuropsychologists receive referrals from parents,
\nschools, and physicians, usually with a very specific question
\nattached (e.g., Is there a language disability Is the person
\nbeginning to show signs of early Alzheimer\u2019s disease). The
\nneuropsychologist will subsequently review the patient\u2019s
\nacademic record or medical chart and schedule an appointment
\nto obtain a case history and administer cognitive tests. The general
\nquestions related to case history are the same for bilinguals
\nand monolinguals: Were there any complications at birth Was
\na learning disability ever suspected What was academic performance
\nlike through school What was the highest level of
\neducation attained What is the employment history Were
\nthere any losses of consciousness Is there any history of
\nsubstance abuse or other psychiatric conditions In some cases,
\nthere will also be a detailed language history for bilinguals, to
\ndetermine which language is dominant, when and how both
\nlanguages were learned, the extent to which both languages are
\ncurrently being used, and other factors (e.g.,Marian,Blumenfeld,
\n& Kaushanskaya, 2007).
\nSubsequently, the neuropsychologist will administer a
\nseries of tests to assess a variety of cognitive domains (e.g.,
\nmental status, IQ, language, memory, executive functions,
\nand visuospatial skills), usually with heavier emphasis on
\ntests that will be useful in answering the specific referral question.
\nOften vocabulary tests are used to estimate verbal IQ,
\npicture naming tests are used to identify the presence of cognitive
\nimpairment, and timed verbal fluency tests are given to
\nlook for frontal lobe pathology (Lezak, 1995). Verbal fluency
\nperformance is sometimes also used to look for patterns of
\nperformance that are associated with certain types of disease
\n(e.g., deficits in semantic fluency are associated with Alzheimer\u2019s
\ndisease whereas deficits in letter fluency are associated
\nBilingual Minds 113
\n113
\nwith Huntington\u2019s disease; Rohrer, Salmon, Wixted, &
\nPaulsen, 1999). Assessment of bilinguals is complicated by
\nthe problem that bilingualism itself influences performance
\non these measures, and it is often not clear what adjustments
\nshould be made to interpret performance relative to that of
\nmonolinguals on the same tests.
\nAssessing vocabulary knowledge in bilinguals
\nA staple of neuropsychological testing is the assessment of
\nvocabulary, but as we have seen in Section 1, bilinguals,
\nespecially bilingual children, often control a smaller vocabulary
\nin each language than comparable monolinguals do, even
\nin the absence of other compromising factors. How can clinical
\nassessment make reliable judgments about the potential for a
\ndisability or disease in contrast to a normal outcome in the
\ncontext of bilingual language use
\nThe approach taken to testing and interpretation often
\ndepends on the nature of the referral question. In some cases,
\nrelatively simple referral questions that can be successfully
\naddressed without much knowledge about bilingualism arise.
\nFor example, parents may wonder how their child\u2019s English
\nvocabulary knowledge compares to that of his or her monolingual
\npeers (note that in bilingual societies this question may be
\nless relevant, particularly if monolinguals are few in number).
\nIn such cases, it is obviously appropriate to administer a test
\nthat was developed for use with monolingual Englishspeaking
\nchildren, and the score obtained will provide a valid
\nanswer to the question being asked. However, the possibility
\nof interpreting that same test score will not extend beyond the
\nanswer to this one simple question. As a group, bilingual
\nchildren who speak a minority language at home (e.g., a non-
\nEnglish language in an English-speaking environment) will
\nobtain lower receptive English vocabulary scores thanwillmonolinguals,
\neven if their parents report that they are \u2018\u2018proficient
\nspeakers of English\u2019\u2019 (Bialystok, Luk, et al., 2010). These lower
\nEnglish vocabulary scoresmay be found even in children without
\nmuch proficiency in the minority homelanguage if the parents are
\nnot native speakers of English, because such children have
\nreduced exposure to English vocabulary at home, at least compared
\nto children whose parents are native English speakers and
\nuse English exclusively.
\nThe difference in vocabulary size in bilinguals is probably
\na better reflection of experience than of ability to learn.
\nIn 6-year-olds, the vocabulary deficit associated with bilingualism
\nseemed to be restricted to test items classified as \u2018\u2018unlikely
\nto occur in a classroom context\u2019\u2019 (Bialystok, Luk, et al., 2010).
\nSimilar results may be obtained in older bilingual children and
\nin bilingual adults and, if so, such information could ultimately
\nbe useful for developing vocabulary tests that cater to specific
\nprofiles of bilingual language exposure. In addition, item
\nanalyses may be useful for interpreting individual test scores.
\nFor example, if a bilingual child misses a home-context item
\n(e.g., \u2018\u2018toaster\u2019\u2019) it may simply mean that there have been no
\nopportunities to learn this word in English because it is unlikely
\nto come up in a school context.
\nAlthough a group of bilinguals will, on average, score lower
\nthan a group of monolinguals, individual scores will not
\nnecessarily be lower. In the large-scale study of \u2018\u2018fluent
\nEnglish-speaking\u2019\u2019 bilingual children between the ages of 3 and
\n10 years (Bialystok, Luk, et al., 2010), the distributions of
\nbilingual and monolingual scores overlapped much more than
\nnot. This means that although the average bilingual score was
\nabout 10 standard score points (2\/3 of a standard deviation)
\nlower than the average monolingual score, only a small number
\nof bilinguals scored completely outside the range of
\nperformance for monolinguals. Thus, the majority of bilingual
\nchildren described as \u2018\u2018fluent in English\u2019\u2019 will obtain \u2018\u2018normal\u2019\u2019
\nscores on tests developed for monolinguals. However, it is also
\nprobable that these same normal scores will fail to provide an
\naccurate representation of learning potential.
\nVocabulary scores reflect the combined forces of the ability
\nto learn new vocabulary and the opportunities to learn new
\nvocabulary. Bilinguals who score within the average range for
\nmonolinguals may have better-than-average ability to learn,
\nwhich has allowed them to achieve an average monolingual
\nscore despite having fewer learning opportunities. An important
\nconsideration in such cases is that comparisons between
\nmonolingual and bilingual children with matched vocabulary
\nscores may be invalid because bilingual children with
\nmonolingual-like vocabulary scores may be precocious learners.
\nConversely, bilinguals whose vocabulary scores fall 2 standard
\ndeviations below the monolingual average could be learning
\ndisabled, or they may simply have had less opportunity to learn
\nEnglish than their case histories suggest\u2014two conclusions
\nwith very different implications but with equally serious
\nconsequences. Bilinguals who score below average may be
\ninaccurately diagnosed with impairment when none is present,
\nor could be diagnosed as \u2018\u2018normal for a bilingual\u2019\u2019 even though
\nimpairment is in fact present and treatment is needed. The lessfrequent
\ncases in which bilinguals obtain scores that are higher
\nthan are typical for monolinguals may indicate exceptional ability
\nto learn vocabulary or more opportunities to learn English
\nthan the case histories suggest\u2014again, two conclusions with
\nvery different implications. Much of this discussion likely
\napplies as well to bilingual adults, who also typically obtain
\nlower vocabulary scores than do monolingual adults (e.g.,
\nBialystok et al., 2008a; Portocarrero et al., 2007).
\nThis discussion demonstrates the tremendous challenge in
\ninterpreting individual test scores in bilinguals. Even with the
\navailability of normative data about bilingual performance on
\na given test, several factors continue to complicate interpretation.
\nFurther difficulty arises if one considers a broader range
\nof bilinguals at different proficiency levels. The previous discussion
\napplies only to children who are judged by their parents
\nto be \u2018\u2018fluent in English.\u2019\u2019 Such children can reasonably be
\ntested in English (and specifically should be tested in English
\nif English is their dominant language). However, even in such
\ncases, a more accurate estimation of language skills will
\nemerge if both languages are tested. Parents may sometimes
\noverestimate the degree of majority-language fluency that their
\nchildren have achieved. Bilinguals who are not dominant in
\n114 Bialystok et al.
\n114
\nEnglish must be tested in their dominant language, but often
\ntests for those languages have not been developed, and there
\nare virtually no tests for different combinations of bilingual
\ntypes. One exception that is available in many different language
\ncombinations is the Bilingual Aphasia Test (the BAT;
\nParadis & Libben, 1987). However, the BAT was designed to
\nassess fluent adult bilinguals for possible language impairment
\n(i.e., aphasia), and it is not known how bilingual children
\nshould perform on this test or even if the test is useful in assessing
\nbilingual adults who don\u2019t have a high degrees of fluency
\nin their two languages.
\nFinally, these simpler cases of \u2018\u2018relatively fluent-in-English
\nbilinguals\u2019\u2019 are perhaps least likely to present for referral in a
\nclinic because they have already been successful in attaining
\nsecond-language fluency. A more typical presentation will be
\nsomeone who seems to be having trouble acquiring secondlanguage
\nfluency. Parents of young preschool children may
\nsuspect a problem if their child seems to be avoiding English
\nspeakers in the classroom, preferring instead to socialize only
\nwith the small number of other children who happen to speak
\nthe same minority language at home. Parents of older schoolaged
\nchildren may become concerned about low academic test
\nscores or large discrepancies between verbal (e.g., reading\/
\nwriting) and less-verbal (e.g., math) academic domains.
\n(Here, \u2018\u2018less verbal\u2019\u2019 is meant to emphasize that all academic
\nsubjects require at least some verbal skills; for example, math
\nproblems sometimes come in paragraph format or require
\nability to read instructions.) In such referral cases, it is necessary
\nto assess what the opportunities to learn English have
\nactually been\u2014sometimes children have actually had less
\nexposure to English than is assumed\u2014and whether or not normal
\namounts of learning have taken place given those opportunities.
\nEven with adequate assessments of opportunities to
\nlearn, test interpretation is difficult because little to no information
\nabout exactly how much exposure is needed to perform
\nwithin a particular range on any given test is available
\nto clinicians.
\nA creative approach around these problems has been to
\nprovide a learning opportunity during the assessment session
\nitself and then to determine how much learning takes place, an
\napproach sometimes called Dynamic Assessment (Gutie\u00b4rrez-
\nClellen & Pen\u02dca, 2001; Pen\u02dca, Iglesias, & Lidz, 2001). This
\napproach is based on interaction between the clinician and the
\nchild. Three types of dynamic assessment are (a) \u2018\u2018testing the
\nlimits,\u2019\u2019 in which feedback is provided and errors pursued
\nthrough further questioning; (b) \u2018\u2018graduated prompting,\u2019\u2019 in
\nwhich the level of contextual support is manipulated; and (c)
\n\u2018\u2018test-teach-retest,\u2019\u2019 in which alternative versions of tests of the
\nsame material are repeated after teaching to areas of weakness,
\nin order to assess learning (Gutie\u00b4rriez-Clellen & Pen\u02dca, 2001).
\nWith these methods the amount of exposure is controlled\u2014it
\nis provided during the testing session itself. Children who fail
\nto learn (i.e., do not show significant improvement on \u2018\u2018measures
\nof modifiability\u2019\u2019; Pen\u02dc a, Resendiz, & Gillam, 2007) are
\nflagged, with a high rate of accuracy, as probable cases of
\ndevelopmental delay. Such techniques are extremely useful for
\nbilinguals and monolinguals alike, and they provide a means
\nfor obtaining accurate assessments with less concern about how
\nto interpret past opportunities to learn.
\nIn theory, bilingual disadvantages in vocabulary knowledge
\nshould decrease with age as their time to learn words in both
\nlanguages increases. Although vocabulary knowledge continues
\nto increase well into older age (Verhaeghen, 2003), new
\nwords may be learned at a faster rate before knowledge reaches
\na particular point (perhaps a typical adult-vocabulary repertoire).
\nIn other words, bilinguals should \u2018\u2018catch up\u2019\u2019 to monolinguals
\nas years of immersion in English accumulate. One way to
\ntest whether this is indeed the case is to ask whether the vocabulary
\ndeficit associated with bilingualism decreases in children
\nas they progress through school and beyond that across
\nthe life-span. Indeed there has been some suggestion that bilingual
\nchildren achieve monolingual-like vocabulary scores with
\nincreased time in school (Hamers & Blanc, 2000). However,
\nthe \u2018\u2018catching up\u2019\u2019 notion is best tested with a longitudinal
\ndesign, and to our knowledge such studies have not been
\nreported. Moreover, bilinguals may appear to be catching up
\nonly because the test materials are not difficult enough to
\nreveal persistent differences between bilinguals and monolinguals.
\nWhen tested exclusively for their knowledge of
\nvery-low-frequency words in the relatively dominant language,
\nfor example in studies of the tip-of-the-tongue phenomenon,
\nadult bilinguals consistently report recognizing fewer of the
\ntargeted vocabulary words than monolinguals do (e.g., Gollan
\n& Silverberg, 2001; Gollan & Brown, 2006). Tip-of-the-tongue
\nexperiences are retrieval failures in which partial phonological
\ninformation is available; they generally occur for
\nlow-frequency words but appear to be more broadly based for
\nbilinguals. Thus, differences between bilinguals and monolinguals
\nin opportunities to learn vocabulary will be less apparent
\nin settings that only require knowledge of relatively easy,
\nfrequently occurring words than they will be in settings that
\nrequire knowledge of difficult, low-frequency words (Gollan
\net al., 2008). This may be because, by virtue of using each
\nlanguage only part of the time, bilinguals will have had
\nrelatively less exposure to words in each language than will
\nmonolinguals (the weaker-links hypothesis described in
\nSection 1), although they will have had sufficient exposure to
\nlearn frequently encountered words.
\nConfrontation naming
\nConfrontation naming is a testing method in which pictures are
\npresented to participants, who are asked to name them as
\nrapidly as possible. One of the most commonly used such
\nneuropsychological tests is the Boston Naming Test (BNT;
\nKaplan et al., 1983). This test contains 60 black-and-white line
\ndrawings that show a single object that speakers try to name.
\nThe pictures are easy at the beginning of the test (e.g., a bed)
\nbut become progressively more difficult, ending with uncommon
\nobjects encountered in limited contexts. The ability to
\nname pictures is sensitive to changes in cognitive functioning
\nand is therefore useful for detecting subtle brain injuries
\nBilingual Minds 115
\n115
\n(Lezak, 1995). Unfortunately, this test may have more limited
\nutility for assessing bilinguals, because cognitively intact bilinguals
\nobtain lower scores than monolinguals on the BNT and
\nother standardized tests of picture naming (e.g., Roberts
\net al., 2002) such as the Expressive Vocabulary Test (e.g.,
\nPortocarrero et al., 2007).
\nOutside of clinical settings, studies of picture naming
\nmeasure both naming success (the number of correct retrievals)
\nand the time needed to name pictures. Such studies reveal a
\nvery subtle bilingual disadvantage (e.g., it may take bilinguals
\n60 milliseconds longer than monolinguals to name a picture;
\nGollan, Bonanni, & Montoya, 2005). This result applies to
\nbilinguals immersed in a dominant but second-learned
\nlanguage (e.g., Gollan et al., 2008) and to bilinguals living in
\na bilingual society (Ivanova & Costa, 2008). Picture-naming
\ndeficits in bilinguals could arise for the same reasons as
\nreceptive vocabulary deficits\u2014namely, less frequency of use
\nof specific words than for monolinguals. Alternatively, it may
\nbe because of dual-language activation\u2014that is, the need to
\nselect one language in the face of competition from the other
\none. It is also possible that both factors may be operating. Some
\nof the burden associated with bilingualism seems to be better
\nmanaged with increased age\u2014a result that is consistent with
\nthe notion of a frequency lag for bilinguals. In one picturenaming
\nstudy, older bilinguals were relatively faster to produce
\nlow-frequency picture names in a nondominant language than
\nwould be expected based on their otherwise relatively slow
\nnaming times relative to proficiency-matched young bilinguals
\n(Gollan et al., 2008). Because low-frequency words in the nondominant
\nlanguage will be most vulnerable to the frequencyof-
\nuse lag associated with bilingualism, these words are also
\nmost likely to benefit from the increased exposure to language
\nassociated with age.
\nThe age-related advantage for producing low-frequency
\nwords is also evident in studies comparing older to younger
\nmonolingual speakers: Like older bilinguals, older monolinguals
\nconsistently produce names for pictures with very low-frequency
\nwords with greater success than matched young monolinguals
\n(for review see Gollan & Brown, 2006). It may be that aging
\nallows for the accumulation of experience to deal with
\nlow-frequency words. The finding that older bilinguals are in
\nsomeways \u2018\u2018better bilinguals\u2019\u2019 than younger bilinguals may seem
\nunexpected from the perspective of bilingualismas an exercise in
\ncognitive control. If the frontal lobes (Raz, 2000;West, 1996) and
\nexecutive control decline in older age and are needed to suppress
\nthe dominant language during retrieval of the nondominant
\nlanguage, then older bilinguals should have more difficulty than
\nyoung bilinguals in producing low-frequencywords in the nondominant
\nlanguage. It might be asked whether older bilinguals
\nperform better because the low-frequency words are archaic
\nwords more familiar to older than to younger participants.
\nHowever, controlled studies select materials that are highly
\nfamiliar to both young and old adults, and in the timed picturenaming
\nstudy with bilinguals, the low-frequency targets were all
\nhighly familiar and current (e.g., crutches, a whistle, a scarf, a
\ndustpan; see appendix in Gollan et al., 2008). Most importantly,
\nthe relative age-related advantage appeared only in the nondominant
\nlanguage, whereas the same concepts and words did not
\ndemonstrate any age-related advantage in the dominant language
\n(or in monolinguals). Thus, it seems that accumulated use over a
\nlifetime has its greatest influence on the very lowest-frequency
\nwords, thereby offsetting some aging-related deficits in retrieval.
\nA number of factors have been shown to reduce or even
\neliminate the bilingual disadvantage in picture naming, and this
\nraises the question of what would be the best way to adjust tests
\nof picture naming to accommodate bilingual ability and enable
\nclinicians to perform reliable assessments. The answer to this
\nquestion may vary with the referral question, and the implications
\nof these findings for diagnosis and treatment of bilinguals
\nare not yet established. For example, bilinguals name pictures
\nmore quickly (Costa, Caramazza, & Sebastia\u00b4n-Galle\u00b4s, 2000;
\nHoshino & Kroll, 2008) and, in some cases, with no disadvantage
\nrelative to monolinguals (Gollan & Acenas, 2004) if the
\ntest consists of pictures with cognate names. Cognates reduce
\nbilingual disadvantages via joint activation of target phonemes
\n(sounds) through separate lexical representations in each
\nlanguage (for a review, see Costa, Santesteban, & Can\u02dco,
\n2005; for research showing increased activation for cognates,
\nsee Broersma & de Bot, 2006). To illustrate, the lexical representations
\nof lemon and its Spanish translation limo\u00b4n activate
\nmany shared sounds, but grape and its translation uva
\nactivate no shared sounds. A similar reduction in bilingual
\ndisadvantage may be obtained by asking participants to retrieve
\nnames of people (Gollan, Bonanni, & Montoya, 2005).
\nBilinguals\u2019 relative ease at producing proper names may have a
\ndifferent mechanism from cognate effects; bilinguals may
\neffectively be monolingual for proper-name production because
\nproper names are generally shared between languages (e.g., Golda
\nMeir is basically the same in Hebrew, English, Spanish, etc).
\nThe finding that bilinguals are better able to name pictures
\nwith cognate names could be useful clinically. One possibility
\nis that bilingual picture-naming tests should focus on cognates
\n(or proper names) for which bilinguals perform much like
\nmonolinguals. However, removing the disadvantage may compromise
\na test as an assessment instrument. For example, the
\npresence of cognate effects on dominant-language production
\nimplies the presence of dual-language activation even when
\nbilinguals are tested exclusively in their relatively more dominant
\nlanguage. Thus, a possible problem with using cognates is
\nthat cognates may increase the extent to which both languages
\nare active, and this may have other undesired effects on test
\nperformance (note that cognate-facilitation effects have also
\nbeen found in bilingual children, but this literature has focused
\nprimarily on receptive vocabulary rather than on picture
\nnaming; August, Carlo, Dressler, & Snow, 2005; Mendez
\nPerez, Pen\u02dc a, & Bedore, in press).
\nSimilar considerations apply to another way to reduce
\nbilingual disadvantages in a testing or assessment situation:
\nto allow bilinguals to use either language to name pictures
\n(Kohnert, Hernandez, & Bates, 1998; Gollan & Silverberg,
\n2001). This approach is sometimes called \u2018\u2018composite\u2019\u2019 or
\n\u2018\u2018conceptual\u2019\u2019 scoring. The scoring method improves
\n116 Bialystok et al.
\n116
\nbilinguals\u2019 picture-naming scores in young adults (Kohnert
\net al., 1998), in elderly bilinguals (Gollan et al., 2007), and
\neven in bilinguals with Alzheimer\u2019s disease (Gollan, Salmon,
\nMontoya, & da Pena, 2010). Thus, when naming is untimed,
\nthe composite scoring option is not associated with any
\nobservable processing cost and only facilitates naming performance.
\nIn timed picture naming, the option to use either language
\nproduces significant language-switching costs but also
\nreveals compelling facilitation effects (Gollan & Ferreira,
\n2009). Specifically, when given the option to use either language,
\nunbalanced bilinguals switch languages in a manner
\nthat resembles a more balanced-bilingual profile of language
\nswitching (i.e., no switch-cost asymmetry; Costa & Santesteban,
\n2004; Costa et al., 2006). In addition, older bilinguals
\nperform much more like young bilinguals in voluntary language
\nswitching, whereas they have considerable difficulty
\nwith cued language switching (Hernandez & Kohnert, 1999).
\nThus, although language mixing might allow bilinguals to communicate
\nbetter in natural settings, it is not necessarily the case
\nthat allowing language mixing and switching in a clinical setting
\nwill lead to more effective diagnosis and treatment, because the
\neither-language scoring methodmay actually obscure differences
\nbetween patients and controls (Gollan et al., 2010),which is counterproductive
\nif the goal is to identify impairments in bilinguals.
\nIn bilingual language assessment, the costs associated with language
\nswitching and mixing can be avoided by testing each language
\nin a separate testing block.
\nThe opposite outcome may be found for cognates. It may be,
\nfor example, that language-impaired bilingual children are less
\nable to benefit from cognate manipulations than typically
\ndeveloping bilingual children are. If this is so, then the ability
\nto benefit from cognate status itself could function as a kind of
\nbilingual-specific litmus test for cognitive impairment. In other
\nwords, failure to demonstrate improved lexical access for cognate
\nwords relative to typically developing bilingual children
\nwould signal some type of language impairment. Importantly,
\nhowever, it is necessary to consider the relative dominance
\nof the two languages for the bilingual child and the relation
\nbetween that dominance and the language of assessment.
\nIn relatively balanced bilinguals, cognates can reduce bilingual
\ndisadvantages in both the dominant and the nondominant
\nlanguages (Gollan & Acenas, 2004; Gollan et al., 2007), but
\nsuch reductions are most robust when bilinguals are tested in
\ntheir nondominant language (e.g., Costa et al., 2000; Gollan
\net al., 2007). A study by van Hell and Dijkstra (2002) using
\nlexical-decision and word-association tasks showed that high
\nlevel of proficiency even in an L3 can influence processing
\nspeed in the dominant language. The clinical significance is
\nthat it is not possible to discount nondominant language
\nknowledge because even an L3 can have an effect on L1 if the
\ndegree of proficiency in the L3 is high enough. Therefore, it is
\npossible that cognate effects in the dominant language occur
\nonly in relatively balanced bilinguals who are also cognitively
\nintact. Alternatively, cognate effects in the nondominant
\nlanguage might be magnified in cognitively impaired bilinguals.
\nAdditional studies are needed to determine the relations between
\ncognate effects on the one hand, and language and cognitive
\nassessment of bilingual children on the other.
\nVerbal fluency in clinical practice
\nResearch using the verbal fluency test as an experimental tool
\nwas described in Section 1. The results showed consistent bilingual
\ndisadvantages on semantic fluency (except when receptive
\nvocabulary knowledge is matched), with somewhat less severe
\nor less certain disadvantages on letter fluency. Clinically, the
\ngreater bilingual disadvantage in semantic fluency than in letter
\nfluency can be misleading, because this is the same pattern of
\nfluency performance that is found in monolinguals with early
\nAlzheimer\u2019s disease as compared with normals (Butters,
\nGranholm, Salmon, Grant, & Wolfe, 1987). This creates a
\ndilemma for neuropsychologists: Is an individual showing
\nsigns of early Alzheimer\u2019s disease or is she simply showing the
\neffects of bilingualism on fluency The verbal fluency test is an
\nimportant instrument in the battery to assess patients for cognitive
\ndecline, so the ambiguity of the results obtained from bilinguals
\npresents a clinical problem. To develop fluency tests for
\nbilingual speakers, it is necessary to understand why semantic
\nfluency is more affected by bilingualism than letter fluency is.
\nAs we explained earlier, letter fluency requires greater recruitment
\nof executive control, perhaps offsetting bilinguals\u2019 disadvantages
\nin lexical retrieval.
\nA different approach to assessing older bilinguals is to use a
\ntask related to verbal fluency, one that reflects semantic
\nprocessing yet distinguishes the cognitive mechanisms that
\nunderlie the effects of bilingualism from those that are involved
\nin Alzheimer\u2019s disease. In the semantic-association task (de
\nGroot, 1989), speakers are given a cue (e.g., \u2018\u2018bride\u2019\u2019) and are
\nasked to produce the first response that comes to mind in
\nrelation to the cue. The overwhelming majority of responses
\nin this task are semantically related to the cues, and this is true
\nfor all speakers, whether they are monolingual or bilingual and
\nwhether or not they are cognitively impaired. However,
\nbilinguals produce slightly but significantly different (or \u2018\u2018less
\ntypical\u2019\u2019) responses than are normally found in monolinguals.
\nFor example, given the cue \u2018\u2018bride,\u2019\u2019 they might say \u2018\u2018pretty\u2019\u2019
\ninstead of the more typical \u2018\u2018groom\u2019\u2019 (Anto\u00b4n-Me\u00b4ndez &
\nGollan, in press). A similar effect was reported in monolinguals
\nwith Alzheimer\u2019s disease as compared to cognitively healthy
\ncontrols (Gollan, Salmon, & Paxton, 2006). To this point,
\ntherefore, there is the same interpretation problem as there is
\nfor verbal fluency, because both bilingualism and Alzheimer\u2019s
\ndisease produce the same outcome. However, further experiments
\nwith the semantic-association task demonstrated that
\nonly the bilingual effect is modulated by lexical frequency.
\nBilinguals produced the same associations as monolinguals
\ndo when the cues were strongly associated to high-frequency
\nwords. In contrast, speakers with Alzheimer\u2019s disease produced
\natypical responses regardless of associate frequency (Anto\u00b4n-
\nMe\u00b4ndez & Gollan, in press). This evidence is consistent
\nwith the notion that Alzheimer\u2019s disease impairs semantic
\nrepresentations themselves (Butters, Salmon, & Heindel,
\nBilingual Minds 117
\n117
\n1990), whereas in bilinguals, difficulty with lexical access can
\nsometimes leads them to perform in ways that imply semantic
\ndeficits when none are present.
\nAs with confrontation naming, there is an important role for
\ncognate status in the performance of verbal-fluency tests, so the
\ninterpretation of results, especially for clinical assessment,
\nneeds to account for this factor. Specifically, in both semantic
\nand letter fluency, bilinguals who speak languages with many
\ncognates spontaneously produce as many cognate responses
\n(e.g., \u2018\u2018lemon\u2019\u2019) as monolinguals do but fewer responses for
\nwords that are not cognates (Sandoval et al., 2010). Put another
\nway, words that are cognates across the two languages are
\ngenerated as often by bilinguals as they are by monolinguals
\nwho only know them in one language, but unique words are
\nproduced less often by bilinguals. In this sense, the greatest
\ndifference in performance is in the lower production of noncognate
\nwords by bilinguals, who appear to have easier access to
\nwords that occur in both their languages. These findings suggest
\nthat bilinguals who speak languages with an extremely high proportion
\nof cognates (e.g.,Catalan-Spanish bilinguals)may exhibit
\nno fluency disadvantage, even for semantic fluency.
\nAnother similarity between verbal fluency and confrontation
\npicture naming is that bilinguals retrieve a greater number of
\nconcept names if they are tested in both languages (Bedore,
\nPen\u02dca, Garci\u00b4a, & Cortez, 2005). However, unlike picture naming
\nin the BNT, fluency scores do not increase if bilinguals are
\nallowed to use whichever language comes to mind during a
\nsingle trial and so to switch between languages (Gollan et al.,
\n2002; De Picciotto & Friedland, 2001). The lack of an improvement
\nin fluency scores when both languages are used may reflect
\nthe costs of language switching. The timing allowed to name
\neach picture in the BNT, about 6 seconds, is too long to detect
\nthe millisecond cost of language switching, so on this task no
\nswitching costs are reported. Presumably, on a more tightly
\ntimed picture-naming task allowing responses in either
\nlanguage, bilinguals would name fewer pictures than would
\nmonolinguals in a fixed amount of time (e.g., 60 seconds),
\nbecause of the additional time needed to carry out the language
\nswitch (Gollan & Ferreira, 2009).
\nBecause bilingualism affects verbal fluency in a number of
\ninteresting ways, there are various possibilities for reducing the
\nbilingual fluency disadvantage. However, reducing this disadvantage
\nmay compromise the reliability of the instrument as
\nan assessment tool for bilinguals, so it is not clear what combination
\nof fluency tests would be most useful for diagnosis of
\ncognitive impairment in bilinguals. Minimally, interpretation
\nof the test scores needs to be modified to accommodate the systematic
\ndifferences that accompany bilingual performance, but
\nultimately it may be possible to develop fluency tests that are
\nspecifically targeted to a bilingual population.
\nThe assessment of executive functions
\nMany of the linguistic skills that bilinguals generally perform
\nmore poorly than monolinguals (reviewed in Section 1) are
\nincluded in typical assessment batteries, often using the same
\ninstruments as those used in research. Therefore, understanding
\nhow to interpret bilingual performance on those tests is a
\ncrucial concern for neuropsychologists. However, in Section 2
\nwe described a variety of nonverbal cognitive tasks on which
\nbilinguals generally perform better than monolinguals. These
\ntasksweremeasures of executive control and, as we have argued,
\nthe experience of bilingual language use has the beneficial outcome
\nof enhancing these levels. What are the clinical implications
\nof this advantage
\nThe implications of this bilingual advantage for clinical
\nassessment are more limited than the bilingual disadvantage
\nin lexical retrieval for several reasons. Perhaps most important
\nis the great emphasis on verbal skills in clinical assessments,
\nwith a more minor role for nonverbal cognitive performance.
\nTherefore, the bilingual advantages found in nonlinguistic
\ntasks will have relatively little effect on the cognitive profiles
\ngenerated in clinical settings. Another important point is that
\nmany of the tasks showing bilingual advantages in experimental
\nstudies (e.g., the Simon task and the Attentional Network
\nTask) are not used in clinical settings.
\nAn important exception is the Stroop color-word-naming
\ntask, which is commonly used to measure attention and is diagnostic
\nof a variety of conditions associated with cognitive
\nimpairment (e.g., Lezak, 1995). As we have seen earlier, bilinguals
\ngenerally suffer less Stroop interference and greater
\nStroop facilitation than monolinguals do (Bialystok et al.,
\n2008a; Herna\u00b4ndez et al., 2010). Several considerations make
\nit difficult to interpret these differences, however. For example,
\nperformance on the Stroop is affected by language proficiency
\n(Tzelgov, Henik, & Leiser, 1990; Rosselli et al., 2002).
\nBecause of this, it is possible that only highly proficient bilinguals
\nwill exhibit the advantage in their dominant language and
\nthat disadvantages may be found if bilinguals are tested in a
\nless dominant language. Equally, it may be that a smaller
\nStroop effect would be found for less-proficient bilinguals,
\nsince the meaning of the color word would be less automatically
\nactivated and therefore less interfering. However,
\nBialystok et al. (2008a) considered that possibility and divided
\neach of the monolingual and bilingual groups into subgroups
\nbased on the speed with which they read the name of the color
\nword when it was written in black ink. The idea was that faster
\nreading times should lead to more interference and therefore a
\nlarger Stroop effect. Therefore, comparing the fast bilingual
\nreaders with the slow monolingual readers should reduce the
\nsize of the Stroop effect, possibly reversing the direction.
\nNonetheless, the analysis showed that bilinguals continued to
\nrecord a smaller Stroop interference effect than did monolinguals,
\neven when considering only the bilinguals for whom
\nreading the English words was the most automatic.
\nThe facilitation effects found for bilinguals in the Stroop
\ntask might be interpreted as a bilingual disadvantage. Increased
\nfacilitation effects have been found in monolinguals with
\nAlzheimer\u2019s disease when compared with healthy controls
\n(Spieler, Balota, & Faust, 1996) and in children when
\ncompared with adults (Wright & Wanley, 2003). The disadvantage
\nview of facilitation is that these effects indicate increased
\n118 Bialystok et al.
\n118
\ninadvertent focus of attention on the word during color
\nnaming (MacLeod & MacDonald, 2000; Spieler et al., 1996).
\nNote, however, that the version of the Stroop task used in
\nexperimental research is not exactly the same as the version
\nused in the clinic. For example, experimental studies typically
\nuse raw interference scores whereas clinic assessment relies on
\na speed-adjusted interference score. Similarly, congruent trials
\nare typically not administered in clinical settings. Therefore,
\nmore information about precisely what types of bilinguals
\nexhibit a Stroop advantage, the origin of bilingual effects on the
\nStroop task, and perhaps most importantly the distribution of
\nscores is needed.
\n5. Bilingualism in the World
\nThe constant use of two languages is an experience that leaves
\nits mark far beyond the immediate and obvious domain of
\ncommunication. As we have seen in this review, it modifies the
\nlevel to which some features of linguistic systems may be
\nlearned and the way in which they are used; it enhances aspects
\nof cognitive processing, particularly those involved in the executive
\ncontrol system; it recruits, and most likely adapts, the
\nneural networks involved in the control of nonverbal processes
\nto modify their use for verbal processes; and it intervenes in
\nclinical assessment by presenting a profile that may not be
\naccurately captured by monolingual norms. These are significant
\nconsequences that cover both individual (e.g., cognitive
\ndevelopment and decline) and public (e.g., assessment and
\ndementia) outcomes. Given this context, the questions posed
\nin this final section concern the implications of bilingualism for
\npublic policy decisions, especially perhaps in the areas of
\neducation and health care. The current prevalence (and rapid
\ngrowth) of bilingualism in today\u2019s highly interconnected world
\nmake these questions relevant and urgent. In light of the
\ndramatic numbers noted in the Introduction, we conclude by
\naddressing specific questions about bilingualism that concern
\nboth individual and social issues.
\nBilingual education
\nNot all parents have the opportunity to expose their children to
\na second language at home, yet many understand the value of
\nbeing able to communicate in another language. One option
\nin these cases is to find alternatives in formal education.
\nA popular program in this regard is immersion education.
\nIn these programs, school instruction takes place in a language
\nthat is not the language of the home or the community (e.g.,
\nFrench instruction in English Canada, Spanish instruction in
\nthe United States) and children are expected to use this language
\nin all their communication with teachers and friends
\nwhile at school. Therefore, children develop fairly high competence
\nin this language, even though they do not typically
\nachieve the level of a native speaker (for review, see Genesee,
\n1985; Johnson & Swain, 1997). But does this limited school
\nexposure make these children \u2018\u2018bilingual\u2019\u2019 by the criteria used
\nin this review and, therefore, affected by the cognitive and linguistic
\noutcomes we have described
\nThe question can be castmore broadly as an inquiry regarding
\nthe degree of bilingualism necessary for the outcomes observed
\nfor more fully functioning bilinguals. There is little evidence on
\nthis point, but the available studies suggest that there is a correlation
\nbetween the degree of bilingualism and the extent of the
\nimpact of bilingualism on cognitive and linguistic processing.
\nEarly studies with children in French immersion programs
\nshowed that both metalinguistic (Bialystok, 1988) and cognitive
\n(Bialystok & Majumder, 1998) outcomes for these children were
\nbetween those found formonolingual children and those found for
\nbilingual children who were fully fluent in both languages.More
\ngenerally,Luk (2008) compared 120 bilingual adultswith varying
\ndegrees of bilingualismto a group of 40monolinguals on linguistic
\nand cognitive outcomes and again found larger effects to be
\nassociated with greater degree of bilingualism.
\nExtending this pattern to education, it is reasonable to
\nassume that there is a cumulative effect of learning language
\nthat, at least in the intense environment of immersion programs,
\nconfers some of the cognitive advantages on children
\neven if they do not become highly fluent speakers. Importantly,
\nthere are few if any costs of immersion education for most children,
\nalthough individual cases may present special challenges
\nthat need to be considered.
\nMore languages, more benefits
\nBilingualism, as we have explained, leads to specific benefits
\nin cognitive processing, and even the limited bilingualism that
\ncomes from immersion education produces some minimal form
\nof this effect. By the same logic, then, does trilingualism lead to
\neven greater benefits than bilingualism, acting as something
\nlike super-bilingualism The evidence on this point is scant.
\nAn interesting study by Kave\u00b4 et al. (2008) compared general
\ncognitive level in a large sample of older adults living in Israel
\nas a function of how many languages they spoke (there were no
\nmonolinguals in the group). They reported significantly higher
\nmaintenance of cognitive status in older age in trilinguals than
\nin bilinguals, and even greater maintenance by multilinguals
\nwho spoke four or more languages than by trilinguals, although
\nthe measure of cognitive level they used was not very precise.
\nSimilarly, others have reported later age of onset of
\nAlzheimer\u2019s disease in multilinguals as compared with bi- and
\ntrilinguals, as we will describe (Chertkow et al., 2010). However,
\nperhaps for bilinguals but almost certainly for
\nmultilinguals, it is possible that people who are able to maintain
\nknowledge of multiple languages may start out advantaged in
\ncertain ways. It is too early to conclude what the effect of knowing
\nmore than two languages might be on cognitive outcomes.
\nA different kind of outcome can be found in language
\nlearning. Monolingual children learning their first language
\nsometimes use a strategy of disambiguation to rapidly
\nfigure out the meaning of new words by assuming that each
\nobject has one unique name, as discussed in Section 1. However,
\nByers-Heinlein and Werker (2009) extended this idea and
\nBilingual Minds 119
\n119
\ncompared 1\u00bd-year-old children who were being raised in
\nmonolingual, bilingual, or trilingual homes. The results
\nshowed a strong reliance on this disambiguation strategy by
\nmonolingual children, amarginal and nonsignificant use of the
\nstrategy by bilingual children, and no evidence at all for this
\nstrategy in trilingual children. Thus, the number of languages
\nin the environment modified children\u2019s expectations about
\nwords and their meanings, possibly setting the stage for
\ndifferent paths of language learning.
\nBilingual aphasia and its treatment
\nAphasia (word-finding difficulties) is the commonest outcome
\nof stroke, and yet our understanding is largely restricted to
\nmonolingual speakers, whereas a significant portion of stroke
\npatients are bilingual\u2014a proportion that is set to increase.
\nClinical management is hampered because there is no current
\nbasis for predicting speech-production difficulties following
\nstroke in bilingual speakers. Recovery patterns are diverse
\n(Green, 2005; Paradis, 2004): For instance, both languages may
\nrecover to the same relative premorbid level (parallel recovery),
\none may recover better than another, or the progressive
\nrecovery of one language may impair the recovery of the other.
\nWithout an understanding of the causal bases of these recovery
\npatterns, including the nature of the control processes involved,
\nthere can be no principled basis for treatment and no rational
\nbasis for identifying the resources required for treatment. For
\ninstance, if treatment in one language (e.g., the L1 or current
\ndominant language) transfers to another, then monolingual
\nspeech therapy could help in the recovery of both languages.
\nHowever evidence on this point is equivocal, largely because
\nthere are few well-controlled studies (see Kohnert, 2009, for
\na recent review). Even the decision to treat in one language
\nrather than two reflects an untested assumption that may or may
\nnot be appropriate to the individual case. For instance, individuals
\nwith a parallel recovery pattern frequently self-cue and
\nproduce a correct word in the nontarget language in order to
\nretrieve the intended word. Proscribing use of the nontreated
\nlanguage may not be justified (Ansaldo, Marcotte, Scherer, &
\nRaboyeau, 2008). A case study reported by Ansaldo, Saidi, and
\nRuiz (2010) exemplifies the value of using the patient\u2019s behavior
\nin both languages and of considering the control processes
\ninvolved. They treated a highly proficient Spanish-English
\nbilingual with a subcortical lesion that included the left caudate.
\nHe had word-finding difficulties in both languages and
\ninvoluntarily switched between languages within conversations
\nwith monolingual partners. On the supposition that distinct
\ncontrol processes mediate translation and speech in just one
\nlanguage (Green, 1986), Ansaldo et al. developed an elegant
\nprocedure (\u2018\u2018switch back through translation\u2019\u2019) that made use
\nof these involuntary language switches and treated the patient
\nsuccessfully.
\nOur review indicates the intimate relationship between
\nlanguage control and the processes of cognitive control. We
\nexpect that successful language recovery will be associated
\nwith a tighter coupling between regions linked to language
\nprocessing and regions (frontal and subcortical) associated with
\ncontrol (Green, 2008). Preliminary data using functional
\nneuroimaging to examine changes in regional coupling during
\nrecovery support this conjecture (Abutalebi, Della Rosa,
\nTettamanti, Green, & Cappa, 2009). If control functions are a
\nstrength of bilingual patients, then treatment should make use
\nof them (Penn, Frankel, Watermeyer, & Russell, 2010). More
\ngenerally, treatments aimed at enhancing or making more
\neffective use of cognitive-control processes may prove to be
\na useful adjunct to conventional treatment derived from
\nresearch on monolingual patients with aphasia.
\nProtection against dementia
\nIn previous sections, we reviewed the evidence showing that
\nbilingual children and adults enjoy an advantage over their
\nmonolingual counterparts in aspects of attention and cognitive
\ncontrol. In some cases (e.g., Bialystok et al., 2004), this bilingual
\nadvantage actually increases in older adulthood, in the
\nsense that performance falls off more steeply with increasing
\nage in monolinguals than it does in bilinguals (see Fig. 3b).
\nThis result may be interpreted as showing that bilingualism
\nserves to protect against some aspects of age-related cognitive
\nloss, and prompts the question of whether bilingualism might
\noffer some protection against pathological decline, specifically
\nagainst the onset of dementia. Such protection might be
\nconsidered one form of \u2018\u2018cognitive reserve\u2019\u2019\u2014the protection
\nof cognitive function by stimulating activities (Stern, 2002).
\nBialystok, Craik, and Freedman (2007) conducted a study of
\nhospital records and found that a sample of 93 lifelong
\nbilinguals experienced the onset of symptoms of dementia
\nsome 4 years later than a comparable sample of 91 monolingual
\npatients. The two groups were essentially equivalent on other
\nfactors that might have influenced the result. This initial study
\nwas followed by another (Craik, Bialystok, & Freedman, 2010)
\nin which approximately 100 bilingual and 100 monolingual
\npatients diagnosed with probable Alzheimer\u2019s disease were
\nquestioned about age of onset and other relevant factors. In this
\nsample, the bilingual group had their first clinic visit more than
\n4 years later than did the monolinguals and had experienced
\nsymptoms of dementia more than 5 years later than their monolingual
\ncounterparts. As in the first study, the groups were
\nequivalent in cognitive level (MMSE score) and the monolinguals
\nhad the greater advantage in terms of education and occupational
\nstatus. There were no differences in these results in
\nsubgroups of immigrants and nonimmigrants. A recent study
\nfrom a Montreal group (Chertkow et al., 2010) has given partial
\nsupport to these first findings. In their investigation, Chertkow
\nand colleagues found a bilingual delay in the onset of symptoms
\nin an immigrant group, as well as in a nonimmigrant
\ngroup whose first language was French, but not in a nonimmigrant
\ngroup whose first language was English. For people who
\nwere multilingual (defined as speaking three or more languages),
\nthe delay of onset was again found.
\nTaking a different approach, Schweizer, Ware, Fischer,
\nCraik, and Bialystok (2010) examined smaller samples of
\n120 Bialystok et al.
\n120
\nmonolingual and bilingual patients diagnosed with probable
\nAlzheimer\u2019s disease who had also received a CT scan. The
\nsamples were matched on cognitive level, so if bilingualism
\nboosts cognitive reserve\u2014maintaining cognitive functions
\ndespite accumulated brain pathology\u2014the bilingual group
\nshould show more evidence of lesion burden. This was
\nexactly the result: The bilingual group showed substantially
\nmore atrophy in temporal regions than did their monolingual
\ncounterparts, although the bilingual patients were still able to
\nfunction at the same cognitive level. These studies support
\nthe possibility that the bilingual advantage in cognitive control
\nextends to benefit patients suffering from Alzheimer\u2019s
\ndisease and also possibly to other forms of dementia. If
\nconfirmed, these findings would make bilingualism one
\nfactor that contributes to cognitive reserve, with effects
\nsimilar to those found for social, intellectual, and physical
\nactivity. How exactly cognitive reserve acts to provide compensation
\nfor brain pathology is an exciting question for
\nfuture research.
\nConclusion
\nAs described earlier, bilingualism is already common in
\nmany parts of the world and is certain to become even more
\ncommon as the 21st century unfolds. We have summarized
\nthe current state of knowledge about language development
\nand cognitive control throughout the lifespan, associated
\nchanges in the brain, and the implications of bilingualism for
\nclinical practice. Much remains to be learned, but it is already
\nclear that the consequences of speaking two or more languages
\nare profound, in some cases dramatically so. As one
\nexample, if the finding that bilingualism delays the onset of
\nAlzheimer\u2019s disease by 4 to 5 years is confirmed by further
\nresearch, there are potentially important implications for the
\nconcept of cognitive reserve. How exactly does bilingualism
\nchange the brain, for example, and which aspects of these
\nchanges confer protection against the onset of dementia
\nOnce this is known, findings from bilingualism research may
\nhelp to focus the search for other environmental conditions
\nwith comparable effects. In the same vein, what about countries
\nsuch as Belgium and the Netherlands, where substantial
\nproportions of the population speak more than one language
\nIs this associated with a generally later onset of Alzheimer\u2019s
\ndisease relative to countries that are largely monolingual
\nOther intriguing questions include ones concerning the
\nlength of time that a person is bilingual: Does learning a second
\nlanguage from infancy provide special benefits, for
\nexample, or is it sufficient to speak two languages consistently
\nfrom the teenage years or even later What about the
\nsimilarities of the two languages Is the bilingual advantage
\ngreater (or less) following the acquisition of highly similar
\nlanguages such as Spanish and Italian compared to such dissimilar
\nlanguages as Chinese and English Given the rapidly
\naccelerating interest in bilingualism as a research topic (sample nursing essay examples by the best nursing assignment writing service),
\nanswers to these and many other questions should be available
\nin the very near future.
\nFunding
\nPreparation of this manuscript was supported by Grant R01
\nHD052523 from the National Institutes of Health to EB, Grant
\nMOP57842 from the Canadian Institutes of Health Research and a
\nGrant from the Alzheimer\u2019s Society of Canada to EB and FIMC, Grant
\n089320\/Z\/09\/Z from the Wellcome Trust to DWG, and Grant R01
\nHD050287 from the National Institutes of Health to THG.
\nReferences
\nAbutalebi, J., Annoni, J.M., Seghier, M., Zimine, I., Lee-Jahnke, H.,
\nLazeyras, F., et al. (2008). Language control and lexical competition
\nin bilinguals: An event-related fMRI study. Cerebral Cortex,
\n18, 1496\u20131505.
\nAbutalebi, J., Brambati, S.M., Annoni, J.M., Moro, A., Cappa, S.F., &
\nPerani, D. (2007). The neural cost of the auditory perception of
\nlanguage switches: An event-related fMRI study in bilinguals.
\nJournal of Neuroscience, 27, 13762\u201313769.
\nAbutalebi, J., Cappa, S.F., & Perani, D. (2001). The bilingual brain as
\nrevealed by functional neuroimaging. Bilingualism: Language and
\nCognition, 4, 179\u2013190.
\nAbutalebi, J., Della Rosa, P.A., Tettamanti, M., Green, D.W., &
\nCappa, S.F. (2009). Bilingual aphasia and language control:
\nA follow-up fMRI and intrinsic connectivity study. Brain and
\nLanguage, 109, 141\u2013156.
\nAbutalebi, J., & Green, D.W. (2007). Bilingual language production:
\nThe neurocognition of language representation and control.
\nJournal of Neurolinguistics, 20, 242\u2013275.
\nAbutalebi, J., Miozzo, A., & Cappa, S.F. (2000). Do subcortical
\nstructures control language selection in bilinguals Evidence from
\npathological language mixing. Neurocase, 6, 101\u2013106.
\nAglioti, S., Beltramello, A., Girardi, F., & Fabbro, F. (1996).
\nNeurolinguistic and follow-up study of an unusual pattern of recovery
\nfrom bilingual subcortical aphasia. Brain, 119, 1551\u20131564.
\nAglioti, S., & Fabbro, F. (1993). Paradoxical selective recovery in a
\nbilingual aphasic following subcortical lesion. Neuroreport, 4,
\n1359\u20131362.
\nAlbert, M.S., Heller, H.S., & Milberg, W. (1988). Changes in naming
\nability with age. Psychology and Aging, 3, 173\u2013178.
\nAlexander, G.E., & Crutcher, M.D. (1990). Functional architecture of
\nbasal ganglia circuits: Neural substrates of parallel processing.
\nTrends in Neuroscience, 13, 266\u2013271.
\nAli, N., Green, D.W., Kherif, F., Devlin, J.T., & Price, C.J. (2010).
\nThe role of the left head of caudate in suppressing irrelevant words.
\nJournal of Cognitive Neuroscience, 22, 2369\u20132386.
\nAltarriba, J., & Heredia, R.R. (2008). An introduction to bilingualism:
\nPrinciples and processes. New York: Erlbaum.
\nAnsaldo, A.I., Marcotte, K., Scherer, L.C., & Raboyeau, G. (2008).
\nLanguage therapy and bilingual aphasia: Clinical implications of
\npsycholinguistic and neuroimaging research. Journal of Neurolinguistics,
\n21, 539\u2013557.
\nAnsaldo, A.I., Saidi, L.G., & Ruiz, A. (2010). Model-driven intervention
\nin bilingual aphasia: Evidence from a case of pathological
\nlanguage mixing. Aphasiology, 24, 309\u2013324.
\nAnto\u00b4n-Me\u00b4ndez, I., & Gollan, T.H. (in press). Not just semantics:
\nStrong frequency and weak cognate effects on semantic association
\nin bilinguals. Memory & Cognition.
\nBilingual Minds 121
\n121
\nAron, A.R., Monsell, S., Sahakian, B.J., & Robbins, T.W. (2004).
\nA componential analysis of task switching deficits associated with
\nlesions of left and right frontal cortex. Brain, 127, 1561\u20131573.
\nAtallah, H.E., Frank, M.J., & O\u2019Reilly, R.C. (2004). Hippocampus,
\ncortex and basal ganglia: Insights from computational models of
\ncomplementary learning systems. Neurobiology, Learning and
\nMemory, 82, 253\u2013267.
\nAu, T.K.-F.,&Glusman,M. (1990). The principle ofmutual exclusivity
\nin word learning: To honor or not to honor Child Development, 61,
\n1474\u20131490.
\nAugust, D., Carlo, M. Dressler, C., & Snow, C. (2005). The critical
\nrole of vocabulary development for English language learners.
\nLearning Disabilities Research & Practice, 20, 50\u201357.
\nBaker, C. (2000). A parents\u2019 and teachers\u2019 guide to bilingualism (2nd
\ned.). Clevedon, England: Multilingual Matters.
\nBates, E., & Goodman, J.C. (1997). On the inseparability of grammar
\nand the lexicon: Evidence from acquisition, aphasia, and real-time
\nprocessing. Language & Cognitive Processes, 12, 507\u2013584.
\nBeauvillain, C., & Grainger, J. (1987). Accessing interlexical homographs:
\nSome limitations of a language-selective access. Journal
\nof Memory and Language, 26, 658\u2013672.
\nBedore, L.M., Pen\u02dca, E.D., Garcia, M., & Cortez, C. (2005).
\nConceptual versus monolingual scoring: When does it make a
\ndifference Language, Speech, and Hearing Services in Schools,
\n36, 188\u2013200.
\nBen-Zeev, S. (1977). The influence of bilingualism on cognitive strategy
\nand cognitive development. Child Development, 48, 1009\u20131018.
\nBialystok, E. (1988). Levels of bilingualism and levels of linguistic
\nawareness. Developmental Psychology, 24, 560\u2013567.
\nBialystok, E. (1992). Attentional control in children\u2019s metalinguistic
\nperformance and measures of field independence. Developmental
\nPsychology, 28, 654\u2013664.
\nBialystok, E. (1999). Cognitive complexity and attentional control in
\nthe bilingual mind. Child Development, 70, 636\u2013644.
\nBialystok, E. (2001). Bilingualism in development: Language.
\nliteracy, and cognition. New York: Cambridge University Press.
\nBialystok, E., Barac, R., Blaye, A., & Poulin-Dubois, D. (2010). Word
\nmapping and executive functioning in young monolingual and
\nbilingual children. Journal of Cognition and Development 11,
\n485\u2013508.
\nBialystok, E., Craik, F.I.M., & Freedman, M. (2007). Bilingualism as
\na protection against the onset of symptoms of dementia. Neuropsychologia,
\n45, 459\u2013464.
\nBialystok, E., Craik, F.I.M., Grady, C., Chau, W., Ishii, R., Gunji, A.,
\n& Pantev, C. (2005). Effects of bilingualism on cognitive control in
\nthe Simon task: Evidence from MEG. NeuroImage, 24, 40\u201349.
\nBialystok, E., Craik, F.I.M., Klein, R., & Viswanathan, M. (2004).
\nBilingualism, aging, and cognitive control: Evidence from the
\nSimon task. Psychology and Aging, 19, 290\u2013303.
\nBialystok, E., Craik, F.I.M., & Luk, G. (2008a). Cognitive control and
\nlexical access in younger and older bilinguals. Journal of Experimental
\nPsychology: Learning, Memory, and Cognition, 34,
\n859\u2013873.
\nBialystok, E., Craik, F.I.M., & Luk, G. (2008b). Lexical access in
\nbilinguals: Effects of vocabulary size and executive control.
\nJournal of Neurolinguistics, 21, 522\u2013538.
\nBialystok, E., Craik, F.I.M., & Ryan, J. (2006). Executive control in a
\nmodified anti-saccade task: Effects of aging and bilingualism.
\nJournal of Experimental Psychology: Learning, Memory, and
\nCognition, 32, 1341\u20131354.
\nBialystok, E., & Feng, X. (2009). Language proficiency and executive
\ncontrol in proactive interference: Evidence from monolingual and
\nbilingual children and adults. Brain and Language, 109, 93\u2013100.
\nBialystok, E., Luk, G., Peets, K.F., & Yang, S. (2010). Receptive
\nvocabulary differences in monolingual and bilingual children.
\nBilingualism: Language and Cognition, 13, 525\u2013531.
\nBialystok, E., & Majumder, S. (1998). The relationship between
\nbilingualism and the development of cognitive processes in
\nproblem-solving. Applied Psycholinguistics, 19, 69\u201385.
\nBialystok, E., & Martin, M.M. (2004). Attention and inhibition in
\nbilingual children: Evidence from the developmental change card
\nsort task. Developmental Science, 7, 325\u2013339.
\nBialystok, E., Martin, M.M., & Viswanathan, M. (2005). Bilingualism
\nacross the lifespan: The rise and fall of inhibitory control. International
\nJournal of Bilingualism, 9, 103\u2013119.
\nBotvinick, M.M., Braver, T.S., Barch, D.M., Carter, C.S., &
\nCohen, J.D. (2001). Conflict monitoring and cognitive control.
\nPsychological Review, 108, 624\u2013652.
\nBraver, T.S., Reynolds, J.R., & Donaldson, D.I. (2003). Neural
\nmechanisms of transient and sustained cognitive control during
\ntask switching. Neuron, 39, 713\u2013726.
\nBrickman, A.M., Paul, R.H., Cohen, R.A., Williams, L.M.,
\nMacGregor, K.L., Jefferson, A.L., et al. (2005). Category and letter
\nverbal fluency across the adult lifespan: Relationship to EEG theta
\npower. Archives of Clinical Neuropsychology, 20, 561\u2013573.
\nBroersma, M., & de Bot, K. (2006). Triggered codeswitching: A
\ncorpus-based Assessment of the original triggering hypothesis and
\na new alternative. Bilingualism: Language and Cognition, 9, 1\u201313.
\nBunge, S.A., Hazeltine, E., Scanlon, M.D., Rosen, A.C., &
\nGabrieli, J.D.E. (2002). Dissociable contributions of prefrontal and
\nparietal cortices to response selection. Neuroimage, 17, 1526\u20131571.
\nBurns, T.C., Yoshida, K.A., Hill, K., & Werker, J.F. (2007). The
\ndevelopment of phonetic representation in bilingual and monolingual
\ninfants. Applied Psycholinguistics, 28, 455\u2013474.
\nButters, N., Granholm, E., Salmon, D.P., Grant, I., &Wolfe, J. (1987).
\nEpisodic and semantic memory: A comparison of amnesic and
\ndemented patients. Journal of Clinical and Experimental Neuropsychology,
\n9, 479\u2013497.
\nButters, N., Salmon, D.P., & Heindel, W.C. (1990). Processes underlying
\nthe memory impairments of demented patients. In Goldberg,
\nE., (Ed.), Contemporary Neuropsychology and the legacy of Luria
\n(pp. 99\u2013126). Hillsdale NJ: Erlbaum.
\nByers-Heinlein, K., & Werker, J.F. (2009). Monolingual, bilingual,
\ntrilingual: Infants\u2019 language experience influences the development
\nof a word-learning heuristic. Developmental Science, 12, 815\u2013823.
\nCaramazza, A. (1997). How many levels of processing are there in
\nlexical access Cognitive Neuropsychology, 14, 177\u2013208.
\nCarlson, S.M., & Meltzoff, A.N. (2008). Bilingual experience and
\nexecutive functioning in young children. Developmental Science,
\n11, 282\u2013298.
\nChee, M.W.L., Soon, C.S., & Ling Lee, H. (2003). Common and segregated
\nneuronal networks for different languages revealed using
\n122 Bialystok et al.
\n122
\nfunctional magnetic resonance adaptation. Journal of Cognitive
\nNeuroscience, 15, 85\u201397.
\nChertkow, H., Whitehead, V., Phillips, N., Wolfson, C., Atherton, J.,
\n& Bergman, H. (2010). Multilingualism (but not always bilingualism)
\ndelays the onset of Alzheimer disease: Evidence from a bilingual
\ncommunity. Alzheimer Disease and Associated Disorders, 24,
\n118\u2013125.
\nChristoff, K., & Gabrieli, J. (2000). The frontopolar cortex and human
\ncognition: Evidence for a rostrocaudal hierarchical organization
\nwithin the human prefrontal cortex. Psychobiology, 28, 168\u2013186.
\nChristoffels, I.K., Firk, C., & Schiller, N.O. (2007). Bilingual
\nlanguage control: An event-related brain potential study. Brain
\nResearch, 1147, 192\u2013208.
\nColome\u00b4, A (2001). Lexical activation in bilinguals\u2019 speech production:
\nLanguage-specific or language-independent Journal of Memory
\nand Language, 45, 721\u2013736.
\nColzato, L.S., Bajo, M.T., van den Wildenberg, W., Paolieri, D.,
\nNieuwenhuis, S., La Heij, W., & Hommel, B. (2008). How does
\nbilingualism improve executive control A comparison of active
\nand reactive inhibition mechanisms. Journal of Experimental
\nPsychology: Learning, Memory, and Cognition, 34, 302\u2013312.
\nConboy, B.T., & Thal, D.J. (2006). Ties between the lexicon and
\ngrammar: Cross-sectional and longitudinal studies of bilingual
\ntoddlers. Child Development, 77, 712\u2013735.
\nConnor, L.T., Spiro, A., Obler, L.K., & Albert, M.L. (2004). Change
\nin object naming ability during adulthood. Journal of Gerontology:
\nPsychological Sciences, 59B, 203\u2013209.
\nCorbetta, M., & Shulman, G.L. (2002). Control of goal-directed and
\nstimulus-driven attention in the brain. Nature Reviews Neuroscience,
\n3, 215\u2013229.
\nCosta, A. (2005). Lexical access in bilingual production. In J.F. Kroll &
\nA.M.B. de Groot (Eds.), Handbook of bilingualism: Psycholinguistic
\napproaches (pp. 308\u2013325). New York: Oxford University Press.
\nCosta, A., Caramazza, A., & Sebastia\u00b4n-Galle\u00b4s, N. (2000). The cognate
\nfacilitation effect: Implications for models of lexical access.
\nJournal of Experimental Psychology: Learning, Memory, and
\nCognition, 26, 1283\u20131296.
\nCosta, A., Herna\u00b4ndez, M., Costa-Faidella, J., & Sebastian-Galles, N.
\n(2009). On the bilingual advantage in conflict processing: Now you
\nsee it, now you don\u2019t. Cognition, 113, 135\u2013149.
\nCosta, A., Herna\u00b4ndez, M., & Sebastia\u00b4n-Galle\u00b4s, N. (2008). Bilingualism
\naids conflict resolution: Evidence from the ANT task. Cognition,
\n106, 59\u201386.
\nCosta, A., Miozzo, M., & Caramazza, A. (1999). Lexical selection in
\nbilinguals: Do words in the bilingual\u2019s two lexicons compete for
\nselection Journal of Memory and Language, 41, 365\u2013397.
\nCosta, A., & Santesteban, M. (2004). Lexical access in bilingual
\nspeech production: Evidence from language switching in highly
\nproficient bilinguals and L2 learners. Journal of Memory and
\nLanguage, 50, 491\u2013511.
\nCosta, A., Santesteban, M., & Can\u02dco, A. (2005). On the facilitatory
\neffects of cognate words in bilingual speech production. Brain and
\nLanguage, 94, 94\u2013103.
\nCosta, A., Santesteban, M., & Ivanova, I. (2006). How do highly proficient
\nbilinguals control their lexicalization process Inhibitory
\nand language specific selection mechanisms are both functional.
\nJournal of Experimental Psychology: Learning, Memory, and Cognition,
\n32, 1057\u20131074.
\nCowan, N. (1999). An embedded process model of working memory.
\nIn A. Miyake & P. Shah (Eds.), Models of working memory
\n(pp. 62\u2013101). New York: Cambridge University Press.
\nCraik, F.I.M. & Bialystok, E. (2006). Cognition through the lifespan:
\nMechanisms of change. Trends in Cognitive Sciences, 10, 131\u2013138.
\nCraik, F.I.M., Bialystok, E., & Freedman, M. (2010). Delaying the
\nonset of Alzheimer\u2019s disease: Bilingualism as a form of cognitive
\nreserve. Neurology.
\nCraik, F.I.M., & Grady, C.L. (2002). Aging, memory and frontal lobe
\nfunctioning. In D.T. Stuss & R.T. Knight (Eds.), Principles of frontal
\nlobe function (pp. 528\u2013540). New York: Oxford University Press.
\nCrinion, J.T., Green, D.W., Chung, R., Ali, N., Grogan, A.,
\nPrice, G.R., et al. (2009). Neuroanotomical markers of speaking
\nChinese. Human Brain Mapping, 30, 4108\u20134115.
\nCrinion, J., Turner, R., Grogan, A., Hanakawa, T., Noppeney, U.,
\nDevlin, J.T., et al. (2006). Language control in the bilingual brain.
\nScience, 312, 1537\u20131540.
\nCrystal, D. (1997). English as a global language. Cambridge,
\nEngland: Cambridge University Press.
\nCummins, J. (1978). Bilingualism and the development of metalinguistic
\nawareness. Journal of Cross-Cultural Psychology, 9, 131\u2013149.
\nCummins, J. (2000). Language, power, and pedagogy. Bilingual
\nchildren in the crossfire. Clevedon, England: Multilingual Matters.
\nDavidson, D., & Tell, D. (2005). Monolingual and bilingual children\u2019s
\nuse of mutual exclusivity in the naming of whole objects. Journal
\nof Experimental Child Psychology, 92, 25\u201345.
\nde Bleser, R., Dupont, P., Postler, J., Bormans, G., Speelman, D.,
\nMortelmans, L., & Debrock, M. (2003). The organisation of the
\nbilingual lexicon: A PET study. Journal of Neurolinguistics, 16,
\n439\u2013456.
\nde Groot, A.M.B. (1989). Representational aspects of word imageability
\nand word frequency as assessed through word association. Journal of
\nExperimental Psychology: Learning, Memory, and Cognition, 15,
\n824\u201345.
\nDehaene, S., & Changeux, J.P. (1991). The Wisconsin Card Sort Test:
\nTheoretical analysis and modelling in a neuronal network.
\nCerebral Cortex, 1, 62\u201379.
\nde Houwer, A. (1995). Bilingual language acquisition. In P. Fletcher
\n& B. MacWhinney (Eds.), Handbook of child language (pp.
\n219\u2013250). London: Blackwell.
\nDelis, D.C., Kaplan, E., & Kramer, J.H. (2001). Verbal fluency subtest
\nof the Delis-Kaplan Executive Function System. San Antonio, TX:
\nThe Psychological Corporation.
\nDempster, F.N. (1992). The rise and fall of the inhibitory mechanism:
\nToward a unified theory of cognitive development and aging.
\nDevelopmental Review, 12, 45\u201375.
\nDe Picciotto, J., & Friedland, D. (2001). Verbal fluency in elderly
\nbilingual speakers: Normative data and preliminary application
\nto Alzheimer\u2019s disease. Folia Phoniatrica et Logopaedica, 53,
\n145\u2013152.
\nDesimone, R., & Duncan, J. (1995). Neural mechanisms of selective
\nattention. Annual Review of Neuroscience, 18, 193\u2013222.
\nde Zubicaray, G., McMahon, K., Eastburn, M., & Pringle, A. (2006).
\nTop-down influences on lexical selection during spoken word
\nBilingual Minds 123
\n123
\nproduction: A 4T fMRI investigation of refractory effects in
\npicture naming. Human Brain Mapping, 27, 864\u201373.
\nDiamond, A. (2002). Normal development of prefrontal cortex
\nfrom birth to young adulthood: Cognitive functions, anatomy,
\nand biochemistry. In D.T. Stuss & R.T. Knight (Eds.), Principles
\nof frontal lobe function (pp. 466\u2013503). New York: Oxford
\nUniversity Press.
\nDosenbach, N.U.F., Visscher, K.M., Palmer, E.D., Miezin, F.M.,
\nWenger, K.K., Kang, H.C., et al. (2006). A core system for the
\nimplementation of task sets. Neuron, 50, 799\u2013812.
\nDraganski, B.,&May, A. (2008). Training-induced structural changes in
\nthe adult human brain. Behavioural Brain Research, 192, 137\u2013142.
\nDufour, R., & Kroll, J.F. (1995). Matching words to concepts in two
\nlanguages: A test of the concept mediation model of bilingual
\nrepresentation. Memory & Cognition, 23, 166\u2013180.
\nDunn, L.M., & Dunn, L.M. (1997). Peabody Picture Vocabulary
\nTest\u2013Third Edition. Bloomington, MN: Pearson Assessments.
\nEimas, P.D., Siqueland, E.R., Jusczyk, P., & Vigorito, J. (1971).
\nSpeech perception in infants. Science, 171, 971\u2013974.
\nEmmorey, K., Luk, G., Pyers, J., & Bialystok, E. (2008). The source of
\nenhanced cognitive control in bilinguals: Evidence from bimodal
\nbilinguals. Psychological Science, 19, 1201\u20131206.
\nFabbro, F., Skrap, M., & Aglioti, S. (2000). Pathological
\nswitching between languages following frontal lesion in a bilingual
\npatient. Journal of Neurology, Neurosurgery, and Psychiatry, 68,
\n650\u2013652.
\nFan, J., Flombaum, J.I., McCandliss, B.D., Thomas, K.M., &
\nPosner, M.I. (2003). Cognitive and brain consequences of conflict.
\nNeuroimage, 18, 42\u201357.
\nFan, J., McCandliss, B. D., Sommer, T., Raz, A., & Posner, M.I.
\n(2002). Testing the efficiency and independence of attentional networks.
\nJournal of Cognitive Neuroscience, 14, 340\u2013347.
\nFeng, X. (2008). Working memory and bilingualism: An investigation
\nof executive control and processing speed. Unpublished doctoral
\ndissertation, York University, Toronto.
\nFeng, X., Diamond, A., & Bialystok, E. (2007). Manipulating information
\nin working memory: An advantage for bilinguals. Poster
\npresented at the biennial meeting of the Society for Research in
\nChild Development, March 29\u2013April 1, 2007, Boston, MA.
\nFennell, C.T., Byers-Heinlein, K., & Werker, J.F. (2007). Using
\nspeech sounds to guide word learning: The case of bilingual
\ninfants. Child Development, 78, 1510\u20131525.
\nFernandes, M.A., Craik, F.I.M., Bialystok, E., & Kreuger, S. (2007).
\nEffects of bilingualism, aging, and semantic relatedness on
\nmemory under divided attention. Canadian Journal of Experimental
\nPsychology, 61, 128\u2013141.
\nFernandez-Duque, D., & Knight, M. (2008). Cognitive control:
\ndynamic, sustained, and voluntary influences. Journal of Experimental
\nPsychology: Human Perception and Performance, 34,
\n340\u2013355.
\nFinkbeiner, M., Almeida, J., Janssen, N., & Caramazza, A. (2006).
\nLexical selection in bilingual speech production does not involve
\nlanguage suppression. Journal of Experimental Psychology:
\nLearning, Memory, and Cognition, 32, 1075\u20131089.
\nFodor, J.A. (1983). The modularity of mind. Cambridge, MA: MIT
\nPress.
\nFrancis, W.S. (1999). Analogical transfer of problem solutions within
\nand between languages in Spanish-English bilinguals. Journal of
\nMemory and Language, 40, 301\u2013329.
\nGalambos, S.J., & Hakuta, K. (1988). Subject-specific and
\ntask-specific characteristics of metalinguistic awareness in bilingual
\nchildren. Applied Psycholinguistics, 9, 141\u2013162.
\nGaser, C., & Schlaug, G. (2003): Brain structures differ between
\nmusicians and non-musicians. Journal of Neuroscience, 23,
\n9240\u20139245.
\nGathercole, V.C.M. (1997). The linguistic mass\/count distinction as
\nan indicator of referent categorization in monolingual and bilingual
\nchildren. Child Development, 68, 832\u2013842.
\nGenesee, F. (1985). Second language learning through immersion:
\nA review of U.S. programs. Review of Educational Research, 55,
\n541\u2013561.
\nGollan, T.H., & Acenas, L.-A.R. (2004). What is a TOT Cognate and
\ntranslation effects on tip-of-the-tongue states in Spanish-English
\nandTagalog-English bilinguals. Journal ofExperimental Psychology:
\nLearning, Memory, and Cognition, 30, 246\u2013269.
\nGollan, T.H., Bonanni, M.P., & Montoya, R.I. (2005). Proper names
\nget stuck on bilingual and monolingual speakers\u2019 tip-of-thetongue
\nequally often. Neuropsychology, 19, 278\u2013287.
\nGollan, T.H., & Brown, A.S. (2006). From tip-of-the-tongue data to
\ntheoretical implications in two steps: When more TOTs means
\nbetter retrieval. Journal of Experimental Psychology: General,
\n135, 462\u2013483.
\nGollan, T.H., Fennema-Notestine, C., Montoya, R.I. & Jernigan, T.L.
\n(2007). The bilingual effect on Boston Naming Test performance.
\nJournal of the International Neuropsychological Society, 13,
\n197\u2013208.
\nGollan, T.H., & Ferreira, V.S. (2009). Should I stay or should I
\nswitch A cost-benefit analysis of voluntary language switching
\nin young and aging bilinguals. Journal of Experimental Psychology:
\nLearning, Memory, & Cognition, 35, 640\u2013665.
\nGollan, T.H., Montoya, R.I., Cera, C., & Sandoval, T.C. (2008). More
\nuse almost always means a smaller frequency effect: Aging,
\nbilingualism, and the weaker links hypothesis. Journal of Memory
\nand Language, 58, 787\u2013814.
\nGollan, T.H., Montoya, R.I., Fennema\u2013Notestine, C., & Morris, S.K.
\n(2005). Bilingualism affects picture naming but not picture
\nclassification. Memory & Cognition, 33, 1220\u20131234.
\nGollan, T.H., Montoya, R.I., & Werner, G.A. (2002). Semantic and
\nletter fluency in Spanish\u2013English bilinguals. Neuropsychology,
\n16, 562\u2013576.
\nGollan, T.H., Salmon, D.P., Montoya, R.I., & da Pena, E. (2010).
\nAccessibility of the nondominant language in picture naming:
\nA counterintuitive effect of dementia on bilingual language
\nproduction. Neuropsychologia, 48, 1356\u20131366.
\nGollan, T.H., Salmon, D.P., & Paxton, J.L. (2006). Word association
\nin early Alzheimer\u2019s Disease. Brain and Language, 99, 289\u2013303.
\nGollan, T.H., & Silverberg, N.B. (2001). Tip-of-the-tongue states in
\nHebrew-English bilinguals. Bilingualism: Language and Cognition,
\n4, 63\u201383.
\nGoral, M., Libben, G., Obler, L., Jarema, G., & Ohayon, K. (2008).
\nLexical attrition in younger and older bilingual adults. Clinical
\nLinguistics & Phonetics, 22, 509\u2013522.
\n124 Bialystok et al.
\n124
\nGrainger, J. (1993). Visual word lexicon in bilinguals. In R. Schreuder
\n& B. Weltens (Eds.), The bilingual lexicon (pp. 11\u201325).
\nAmsterdam: John Benjamins.
\nGraybiel, A.M. (2000). The basal ganglia. Current Biology, 10,
\n509\u2013511.
\nGreen, D.W. (1986). Control, activation and resource. Brain and
\nLanguage, 27, 210\u2013223.
\nGreen, D.W. (1998). Mental control of the bilingual lexico-semantic
\nsystem. Bilingualism: Language and Cognition, 1, 67\u201381.
\nGreen, D.W. (2005). The neurocognition of recovery patterns in
\nbilingual aphasics. In J.F. Kroll & A.M.B. de Groot (Eds.), Handbook
\nof bilingualism: Psycholinguistic perspectives (pp. 516\u2013530).
\nNew York: Oxford University Press.
\nGreen, D.W. (2008). Bilingual aphasia: Adapted language
\nnetworks and their control. Annual Review of Applied Linguistics,
\n28, 25\u201348.
\nGrogan, A., Green, D.W., Ali, N., Crinion, J.T., & Price, C. (2009).
\nStructural correlates of semantic and phonemic fluency ability in
\nfirst and second languages. Cerebral Cortex, 19, 2690\u20132698.
\nGrosjean, F. (1998). Studying bilinguals: Methodological and conceptual
\nissues. Bilingualism: Language and Cognition, 1, 131\u2013140.
\nGutie\u00b4rrez-Clellen, V., & Pen\u02dca, E. (2001). Dynamic assessment of
\ndiverse children: A tutorial. Language, Speech, and Hearing
\nServices in Schools, 32, 212\u2013224.
\nGuttentag, R.E., Haith, M.M., Goodman, G.S., & Hauch, J. (1984).
\nSemantic processing of unattended words by bilinguals: A test of
\nthe input switch mechanism. Journal of Verbal Learning and
\nVerbal Behavior, 23, 178\u2013188.
\nHamers, J., & Blanc, M. (2000). Bilinguality and bilingualism (2nd
\ned.). Cambridge, MA: Cambridge University Press.
\nHamilton, C.A., & Martin, R.C. (2005). Dissociations among tasks
\ninvolving inhibition: A single case study. Cognitive, Affective, &
\nBehavioral Neuroscience, 5, 1\u201313.
\nHernandez, A.E. (2009). Language switching in the bilingual brain:
\nWhat\u2019s next Brain & Language, 109, 133\u2013140.
\nHernandez, A.E., Bates, E., & Avila, L.X. (1996). Processing across
\nthe language boundary: A cross-modal priming study of Spanish-
\nEnglish bilinguals. Journal of Experimental Psychology: Learning,
\nMemory, and Cognition, 22, 846\u2013864.
\nHernandez, A.E., Dapretto, M., & Bookheimer, S. (2001). Language
\nswitching and language representation in Spanish-English
\nbilinguals: An fMRI study. NeuroImage, 14, 510\u2013520.
\nHernandez, A.E., & Kohnert, K.J. (1999). Aging and language
\nswitching in bilinguals. Aging, Neuropsychology, and Cognition,
\n6, 69\u201383.
\nHernandez, A.E., Martinez, A., & Kohnert, K. (2000). In search of the
\nlanguage switch: An fMRI study of picture naming in Spanish-
\nEnglish bilinguals. Brain and Language, 73, 421\u2013431.
\nHernandez, A.E., & Meschyan, G. (2006). Executive function is
\nnecessary to enhance lexical processing in a less proficient L2:
\nEvidence from fMRI during picture naming. Bilingualism:
\nLanguage and Cognition, 9, 177\u2013188.
\nHerna\u00b4ndez, M., Costa, A., Fuentes, L.J., Vivas, A.B., Sebastia\u00b4n-
\nGalle\u00b4s, N., (2010). The impact of bilingualism on the executive
\ncontrol and orienting networks of attention. Bilingualism: Language
\nand Cognition, 13, 315\u2013325.
\nHerna\u00b4ndez, M., Martin, C., Barcelo, F., & Costa, A. (2010). To switch
\nor not to switch: On the impact of bilingualism in task-switching.
\nManuscript submitted for publication.
\nHerschmann, H., & Po\u00a8 tzl, O. (1920). Bemerkungen \u00a8uber die Aphasie
\nder Polyglotten. Zentralblatt Neurologie, 39, 114\u2013128.
\nHoshino, N., & Kroll, J. F. (2008). Cognate effects in picture naming:
\nDoes cross-language activation survive a change of script
\nCognition, 106, 501\u2013511.
\nHyafil, A., Summerfield, C., & Koechlin, E. (2009). Two mechanisms
\nfor task switching in the prefrontal cortex. Journal of
\nNeuroscience, 29, 5135\u20135142.
\nIvanova, I., & Costa, A. (2008). Does bilingualism hamper lexical
\naccess in speech production Acta Psychologica, 127, 277\u2013288.
\nJackson, G.M., Swainson, R., Cunnington, R., & Jackson, S.R. (2001).
\nERP correlates of executive control during repeated language
\nswitching. Bilingualism: Language and Cognition, 4, 169\u2013178.
\nJacoby, L.L. (1991). A process dissociation framework: Separating
\nautomatic from intentional uses of memory. Journal of Memory
\nand Language, 30, 513\u2013541.
\nJimura, K., & Braver, T.S. (2010). Age-related shifts in brain activity
\ndynamics during task switching. Cerebral Cortex, 20, 1420\u20131431.
\nJohnson, R.K.,&Swain, M. (1997). Immersion education: International
\nperspectives. Cambridge, England: Cambridge University Press.
\nKane, M.J., & Engle, R.W. (2000). Working-memory capacity,
\nproactive interference, and divided attention: Limits on
\nlong-term memory retrieval. Journal of Experimental Psychology:
\nLearning, Memory, & Cognition, 26, 336\u2013358.
\nKaplan, E., Goodglass, H., & Weintraub, S. (1983). The Boston
\nNaming Test. Philadelphia: Lea & Febiger.
\nKave\u00b4, G, Eyal, N., Shorek, A., & Cohen-Mansfield, J. (2008).
\nMultilingualism and cognitive state in the oldest old. Psychology
\nand Aging, 23, 70\u201378.
\nKerns, J.G., Cohen, J.D.,MacDonald, A.W., Cho, R.Y., Stenger, V.A.,
\n& Carter, C.S. (2004). Anterior cingulate conflict monitoring and
\nadjustments in control. Science, 303, 1023\u20131026.
\nKimberg, D.Y., D\u2019Esposito, M., & Farah, M.J. (1997). Effects of
\nbromocriptine on human subjects depend on working memory
\ncapacity. NeuroReport, 8, 3581\u20133585.
\nKlein, D., Milner, B., Zatorre, R.J., Meyer, E., & Evans, A.C. (1995).
\nThe neural substrates underlying word generation: A bilingual
\nfunctional-imaging study. Proceedings of the National Academy
\nof Sciences, USA, 92, 2899\u20132903.
\nKohnert, K. (2007). Language Disorders in Bilingual Children and
\nAdults. San Diego, CA: Plural Publishing, Inc.
\nKohnert, K. (2009). Cross-language generalization following
\ntreatment in bilingual speakers with aphasia: A review. Seminars
\nin Speech and Language, 30, 174\u2013186.
\nKohnert, K.J., Hernandez, A.E., & Bates, E. (1998). Bilingual performance
\non the Boston Naming Test: Preliminary norms in Spanish
\nand English. Brain and Language, 65, 422\u2013440.
\nKotz, S.A., Schwartze, M., & Schmidt-Kassow, M. (2009). Non-motor
\nbasal ganglia functions: A review and proposal for a model of sensory
\npredictability in auditory language perception. Cortex, 45,
\n982\u2013990.
\nKova\u00b4cs, A\u00b4 .M., & Mehler, J. (2009a). Flexible learning of multiple
\nspeech structures in bilingual infants. Science, 325, 611\u2013612.
\nBilingual Minds 125
\n125
\nKova\u00b4cs, A\u00b4 .M., & Mehler, J. (2009b). Cognitive gains in 7-month-old
\nbilingual infants. Proceedings of the National Academy of
\nSciences, USA, 106, 6556\u20136560.
\nKovelman, I., Baker, S.A., & Petitto, L.-A. (2008). Bilingual and
\nmonolingual brains compared: A functional magnetic resonance
\ninvestigation of syntactic processing and a possible \u2018\u2018neural signature\u2019\u2019
\nof bilingualism. Journal of Cognitive Neuroscience, 20, 153\u2013169.
\nKovelman, I., Shalinsky, M.H., White, K.S., Schmit, S.N.,
\nBerens, M.S., Paymer, N., & Petitto, L.-A. (2009). Dual language
\nuse in sign-speech bimodal bilinguals: fNIRS brain\u2013imaging
\nevidence. Brain & Language, 109, 112\u2013123.
\nKroll, J.F., Bobb, S.C., Misra, M., & Guo, T. (2008). Language
\nselection in bilingual speech: Evidence for inhibitory processes.
\nActa Psychologica, 128, 416\u2013430.
\nKroll, J.F., Bobb, S.C., & Wodniecka, Z. (2006). Language selectivity
\nis the exception, not the rule: Arguments against a fixed locus of
\nlanguage selection in bilingual speech. Bilingualism: Language
\nand Cognition, 9, 119\u2013135.
\nKroll J.F., & de Groot, A. (Eds.). (2005). Handbook of Bilingualism:
\nPsycholinguistic Approaches. New York: Oxford University Press.
\nKroll, J.F., & de Groot, A.M.B. (1997). Lexical and conceptual
\nmemory in the bilingual: Mapping form to meaning in two
\nlanguages. In A.M.B. de Groot & J.F. Kroll (Eds.), Tutorials in
\nbilingualism (pp. 169\u2013199). Mahwah, NJ: Erlbaum.
\nKroll, J.F., & Stewart, E. (1994). Category interference in translation
\nand picture naming: Evidence for asymmetric connections between
\nbilingual memory representations. Journal of Memory and
\nLanguage, 33, 149\u2013174.
\nKuhl, P.K., Stevens, E., Hayashi, A., Deguchi, T., Kiritani, S., &
\nIverson, P. (2006). Infants show a facilitation effect for native
\nlanguage phonetic perception between 6 and 12 months. Developmental
\nScience, 9, F13\u2013F21.
\nLa Heij, W. (1988). Components of Stroop-like interference in picture
\nnaming. Memory and Cognition, 16, 400\u2013410.
\nLa Heij, W. (2005). Selection processes in monolingual and bilingual
\nlexical access. In J.F. Kroll & A.M.B. de Groot (Eds.), Handbook
\nof bilingualism: Psycholinguistic approaches (pp. 289\u2013307). New
\nYork: Oxford University Press.
\nLau, H., Rogers, R.D., & Passingham, R.E. (2006). Dissociating
\nresponse selection and conflict in the medial frontal surface.
\nNeuroImage, 29, 446\u2013451.
\nLee, H., Devlin, J.T., Shakeshaft, C., Stewart, L.H., Brennan, A.,
\nGlensman, J., et al. (2007). Anatomical traces of vocabulary acquisition
\nin the adolescent brain. Journal of Neuroscience, 27, 1184\u20131189.
\nLehtonen, M., Laine, M., Niemi, J., Thomson, T., Vorobyev, V.A., &
\nHughdal, K. (2005). Brain correlates of sentence translation in
\nFinnish-Norwegian bilinguals. NeuroReport, 16, 607\u2013610.
\nLeischner, A. (1983). On the aphasia of multilinguals. In M. Paradis
\n(Ed.), Readings on aphasia in bilinguals and polyglots (pp. 456\u2013
\n502). Montreal: Didier. (Original work published 1948).
\nLevy, B.J., McVeigh, N.D., Marful, A., & Anderson, M.C. (2007).
\nInhibiting your native language: The role of retrieval-induced
\nforgetting during second language acquisition. Psychological
\nScience, 18, 29\u201334.
\nLezak, M.D. (1995). Neuropsychological assessment. (3rd ed.). New
\nYork: Oxford University Press.
\nLi, C.S., Yan, P., Sinha, R., & Lee, T.W. (2008). Subcortical processes
\nof motor response inhibition during a stop signal task. Neuro-
\nImage, 41, 1352\u20131363.
\nLinck, J.A., Kroll, J.F., & Sunderman, G. (2009). Losing access to the
\nnative language while immersed in a second language. Psychological
\nScience, 20, 1507\u20131515.
\nLiu, X., Banich, M.T., Jacobson, B.L., & Tanabe, J.L. (2004).
\nCommon and distinct neural substrates of attentional control in
\nan integrated Simon and spatial Stroop task as assessed by eventrelated
\nfMRI. NeuroImage, 22, 1097\u20131106.
\nLuce, P.A., & Large, N.R. (2001). Phonotactics, density, and entropy
\nin spoken word recognition. Language and Cognitive Processes,
\n16, 565\u2013581.
\nLuk, G. (2008). The anatomy of the bilingual influence of cognition:
\nLevels of functional use and proficiency of language. Unpublished
\ndoctoral dissertation, York University, Toronto.
\nLungu, O.V., Binenstock, M.M., Pline, M.A., Yeaton, J.R., &
\nCarey, J.R. (2007). Neural changes in control implementation of
\na continuous task. Journal of Neuroscience, 27, 3010\u20133016.
\nLuo, L., Luk, G., & Bialystok, E. (2010). Effect of language
\nproficiency and executive control on verbal fluency performance
\nin bilinguals. Cognition, 114, 29\u201341.
\nMacDonald, A.W., Cohen, J.D., III, Stenger, V.A., & Carter, C.S.
\n(2000). Dissociating the role of the dorsolateral prefrontal and anterior
\ncingulate cortex in cognitive control. Science, 288, 1835\u20131838.
\nMacLeod, C.M., & MacDonald, P.A. (2000). Interdimensional
\ninterference in the Stroop effect: Uncovering the cognitive and
\nneural anatomy of attention. Trends in Cognitive Sciences, 4,
\n383\u2013391.
\nMaguire, E.A., Gadian, D.G., Johnsrude, I.S., Good, C.D.,
\nAshburner, J., Frackowiak, R.S., & Frith, C.D. (2000).
\nNavigation-related structural change in the hippocampi of taxi
\ndrivers. Proceedings of the National Academy of Sciences, USA,
\n97, 4398\u20134403.
\nMahon, B.Z., Costa, A., Peterson, R., Vargas, K., & Caramazza, A.
\n(2007). Lexical selection is not by competition: A reinterpretation
\nof semantic interference and facilitation effects in the picture-word
\ninterference paradigm. Journal of Experimental Psychology:
\nLearning, Memory, and Cognition, 33, 503\u2013535.
\nMarian, V., Blumenfeld, H.K., & Kaushanskaya, M. (2007). The
\nlanguage experience and proficiency questionnaire (LEAP\u2013Q):
\nAssessing language profiles in bilinguals and multilinguals.
\nJournal of Speech, Language, and Hearing Research, 50, 940\u2013967.
\nMarian, V., Spivey, M., & Hirsch, J. (2003). Shared and separate
\nsystems in bilingual language processing: Converging evidence from
\neyetracking and brain imaging. Brain and Language, 86, 70\u201382.
\nMarie\u00a8n, P., Abutalebi, J., Engelborghs, S., & De Deyn, P.P. (2005).
\nAcquired subcortical bilingual aphasia in an early bilingual child:
\nPathophysiology of pathological language switching and language
\nmixing. Neurocase, 11, 385\u2013398.
\nMarkman, E.M., & Wachtel, G.F. (1988). Children\u2019s use of mutual
\nexclusivity to constrain themeanings ofwords. CognitivePsychology,
\n20, 121\u2013157.
\nMartin, C.D., Dering, B., Thomas, E.M., & Thierry, G. (2009). Brain
\npotentials reveal semantic priming in both the \u2018active\u2019 and the \u2018nonattended\u2019
\nlanguage of early bilinguals. NeuroImage, 47, 326\u2013333.
\n126 Bialystok et al.
\n126
\nMartin-Rhee, M.M., & Bialystok, E. The development of two types
\nof inhibitory control in monolingual and bilingual children.
\nBilingualism: Language and Cognition, 11, 81\u201393.
\nMattock, K., Polka, L., Rvachew, S.,&Krehm,M. (2010). The first steps
\nin word learning are easier when the shoes fit: Comparing monolingual
\nand bilingual infants. Developmental Science, 13, 229\u2013243.
\nMayr, U., & Liebscher, T. (2001). Is there an age deficit in the
\nselection of mental sets European Journal of Cognitive Psychology,
\n13, 47\u201369.
\nMechelli, A., Crinion, J.T., Noppeney, U., O\u2019Doherty, J., Ashburner, J.,
\nFrackowiak, R.S., & Price, C.J. (2004). Neurolinguistics: Structural
\nplasticity in the bilingual brain. Nature, 431, 757.
\nMeiran, N., & Gotler, A. (2001). Modelling cognitive control in task
\nswitching and ageing. European Journal of Cognitive Psychology,
\n13, 165\u2013186.
\nMeisel, J.M. (1990). Grammatical development in the simultaneous
\nacquisition of two first languages. In J.M. Meisel (Ed.), Two first
\nlanguages: Early grammatical development in bilingual children
\n(pp. 5\u201320). Dordrecht, Holland: Foris Publications.
\nMendez Perez, A., Pen\u02dca, E.D., & Bedore, L.M. (in press). Cognates
\nfacilitate word recognition in young Spanish-English bilinguals\u2019
\ntest performance. Early Childhood Services.
\nMerriman, W.E., & Kutlesic, V. (1993). Bilingual and monolingual
\nchildren\u2019s use of two lexical acquisition heuristics. Applied Psycholinguistics,
\n14, 229\u2013249.
\nMeuter, R.F.I., & Allport, A. (1999). Bilingual language switching in
\nnaming: Asymmetrical costs of language selection. Journal of
\nMemory and Language, 40, 25\u201340.
\nMiller, E., & Cohen, J. (2001). An integrative theory of prefrontal cortex
\nfunction. Annual Review of Neuroscience, 24, 167\u2013202.
\nMink, J.W. (1996). The basal ganglia: Focused selection and inhibition
\nof competing motor programs. Progress in Neurobiology,
\n50, 381\u2013425.
\nMirman, D., & Magnuson, J.S. (2008). Attractor dynamics and semantic
\nneighborhood density: Processing is slowed by near neighbors
\nand speeded by distant neighbors. Journal of Experimental
\nPsychology: Learning, Memory, and Cognition, 34, 65\u201379.
\nMisra, M., Guo, T., Bobb, S., & Kroll, J.F. (2007, May). Electrophysiological
\ncorrelates of bilingual word production. Poster presented
\nat the Annual Meeting of the Cognitive Neuroscience
\nSociety, New York, NY.
\nMoritz-Gasser, S., & Duffau, H. (2009a). Direct evidence for a
\nlarge-scale network underlying language switching in vivo in
\nhumans. Journal of Neurosurgery, 111, 729\u2013732.
\nMoritz-Gasser, S., & Duffau, H. (2009b). Cognitive processes and
\nneural basis of language switching: Proposal of a new model.
\nNeuroReport, 20, 1577\u20131580.
\nNee, D.E., Wager, T.D., & Jonides, J. (2007). Interference resolution:
\nInsights from a meta-analysis of neuroimaging tasks. Cognitive,
\nAffective, & Behavioral Neuroscience, 7, 1\u201317.
\nNosarti, C., Mechelli, A., Green, D.W., & Price, C.J. (2010). The
\nimpact of second language learning on semantic and nonsemantic
\nfirst language reading. Cerebral Cortex, 20, 315\u2013327.
\nParadis, J., & Genesee, F. (1996). Syntactic acquisition in bilingual
\nchildren: Autonomous or interdependent Studies in Second
\nLanguage Acquisition, 18, 1\u201325.
\nParadis, M. (2004). Neurolinguistic aspects of bilingualism.
\nAmsterdam: Benjamins.
\nParadis, M. (2008). Bilingualism and neuropsychiatric disorders.
\nJournal of Neurolinguistics, 21, 199\u2013230.
\nParadis, M. (2009). Declarative and procedural determinants of
\nsecond languages (Studies in Bilingualism 40). Amsterdam, the
\nNetherlands: John Benjamins.
\nParadis, M., & Libben, G. (1987). The assessment of bilingual
\naphasia. Hillsdale, NJ: Lawrence Erlbaum.
\nParsons, M.W., Harrington, D.L., & Rao, S.M. (2005). Distinct neural
\nsystems underlie learning visuomotor and spatial representations
\nof motor skills. Human Brain Mapping, 24, 229\u2013247.
\nPashler, H. (2000). Task switching and multitask performance. In
\nS. Monsell & J. Driver (Eds.), Attention and Performance XVII:
\nControl of mental processes (pp. 309\u2013330). Cambridge, MA:
\nMIT Press.
\nPaxton, J.L., Barch, D.M., Racine, C.A., & Braver, T.S. (2008). Cognitive
\ncontrol, goal maintenance and prefrontal function in healthy
\nageing. Cerebral Cortex, 18, 1010\u20131028.
\nPeal, E., & Lambert, W. (1962). The relation of bilingualism to intelligence.
\nPsychological Monographs: General and Applied, 76, 1\u201323.
\nPearson, B.Z., & Fernandez, S.C. & Oller, D.K. (1993). Lexical
\ndevelopment in bilingual infants and toddlers: Comparison to
\nmonolingual norms. Language Learning, 43, 93\u2013120.
\nPen\u02dca, E.D., & Bedore, L. (2009). Child language disorders in bilingual
\ncontexts. In R. Schwartz (Ed.), Handbook of Child Language
\nDisorders (pp. 281\u2013307). New York: Psychology Press.
\nPen\u02dc a, E.D., Iglesias, A., & Lidz, C.S. (2001). Reducing test
\nbias through dynamic assessment of children\u2019s word learning
\nability. American Journal of Speech Language Pathology, 10,
\n138\u2013154.
\nPen\u02dca, E.D., Resendiz, M., & Gillam, R.B. (2007). The role of clinical
\njudgments of modifiability in the diagnosis of language impairment.
\nAdvances in Speech\u2013Language Pathology, 8, 1\u201314.
\nPenn, C., Frankel, T., & Watermeyer, J. & Russell, N. (2010). Executive
\nfunction and conversational strategies in bilingual aphasia.
\nAphasiology, 24, 288\u2013308.
\nPeterson, B.S., Kane, M.J., Alexander, G.M., Lacadie, C.,
\nSkudlarski, P., Leung, H.C., et al. (2002). An event-related functional
\nMRI study comparing interference effects in the Simon and
\nStroop tasks. Cognitive Brain Research, 13, 427\u2013440.
\nPetitto, L.A. (1987). On the autonomy of language and gesture:
\nEvidence from the acquisition of personal pronouns in American
\nSign Language. Cognition, 27, 1\u201352.
\nPetitto, L.A., Katerelos, M., Levy, B.G., Gauna, K., Tetreault, K., &
\nFerraro, V. (2001). Bilingual signed and spoken language acquisition
\nfrom birth: Implications for the mechanisms underlying early bilingual
\nlanguage acquisition. Journal of Child Language, 28, 453\u2013496.
\nPhilipp, A.M., Gade, M., & Koch, I. (2007). Inhibitory processes in
\nlanguage switching: Evidence from switching language-defined
\nresponse sets. European Journal of Cognitive Psychology, 19,
\n395\u2013416.
\nPhilipp, A.M., & Koch, I. (2009). Inhibition in language switching:
\nWhat is inhibited when switching between languages in naming
\ntasks Journal of Experimental Psychology: Learning, Memory,
\nand Cognition, 35, 1187\u20131195.
\nBilingual Minds 127
\n127
\nPonto\u00b4n, M., & Leo\u00b4n-Carrio\u00b4n, J. (2001). Neuropsychology and the
\nHispanic (the best nursing writing service, a studybay for your papers) patient: A clinical handbook. Mahwah, NJ: Erlbaum.
\nPortocarrero, J.S., & Burright, R.G. & Donovick, P.J. (2007). Vocabulary
\nand verbal fluency of bilingual and monolingual college
\nstudents. Archives of Clinical Neuropsychology, 22, 415\u2013422.
\nPosner, M.I., & Petersen, S.E. (1990). The attention system of the
\nhuman brain. Annual Review of Neuroscience, 13, 25\u201342.
\nPo\u00a8 tzl, O. (1925). U\u00a8 ber die parietal bedingte Aphasie und ihren
\nEinfluss auf das Sprechen mehrerer Sprachen. Zeitschrift f \u00a8 ur die
\ngesamte Neurologie und Psychiatrie, 99, 100\u2013124.
\nPo\u00a8 tzl, O. (1930). Aphasie und Mehrsprachigkeit. Zeitschrift f \u00a8 ur die
\ngesamte Neurologie und Psychiatrie, 124, 145\u2013162.
\nPoulisse, N. (1997). Language production in bilinguals. In A.M.B. de
\nGroot & F.J. Kroll (Eds.), Tutorials in bilingualism: Psycholinguistic
\nperspectives (pp. 201\u2013224). Mahwah, NJ: Erlbaum.
\nPoulisse, N., & Bongaerts, T. (1994). First language use in second
\nlanguage production. Applied Linguistics, 15, 36\u201357.
\nPrice, C.J., Green, D., & von Studnitz, R.A. (1999). Functional
\nimaging study of translation and language switching. Brain, 122,
\n2221\u20132236.
\nPrior, A., & Gollan, T.H., (2010). What monolinguals reveal about
\nbilingual language control: Task- and language-switching in
\nmonolinguals, Spanish-English and Mandarin-English bilinguals.
\nManuscript submitted for publication.
\nPrior, A., & MacWhinney, B. (2010). A bilingual advantage in task
\nswitching. Bilingualism: Language and Cognition, 13, 253\u2013262.
\nRansdell, S.E., & Fischler, I. (1987). Memory in a monolingual mode:
\nWhen are bilinguals at a disadvantage Journal of Memory &
\nLanguage, 26, 392\u2013405.
\nRaz, N. (2000). Aging of the brain and its impact on cognitive
\nperformance: Integration of structural and functional findings. In
\nF.I.M. Craik & T.A. Salthouse (Eds.), The handbook of aging and
\ncognition (2nd ed., pp. 1\u201390). Mahwah, NJ: Erlbaum.
\nReimers, S., & Maylor, E.A. (2005). Task switching across the life
\nspan: Effects of age on general and specific switch costs. Developmental
\nPsychology, 41, 661\u2013671.
\nRicciardelli, L.A. (1992). Bilingualism and cognitive development in
\nrelation to threshold theory. Journal of Psycholinguistic Research,
\n21, 301\u2013316.
\nRinne, J.O., Tommola, J., Laine, M., Krause, B.J., Schmidt, D.,
\nKaasinen, V., et al. (2000). The translating brain: Cerebral
\nactivation patterns during simultaneous interpreting. Neuroscience
\nLetters, 294, 85\u201388.
\nRivera Mindt, M., Arentoft, A., Kubo Germano, K., D\u2019Aquila, E.,
\nScheiner, D., Pizzirusso, M., et al. (2008). Neuropsychological,
\ncognitive, and theoretical considerations for Assessment of bilingual
\nindividuals. Neuropsychology Review, 18, 255\u2013268.
\nRoberts, P.M., Garcia, L.J., Desrochers, A., & Hernandez, D. (2002).
\nEnglish performance of proficient bilingual adults on the Boston
\nNaming Test. Aphasiology, 16, 635\u2013645.
\nRoberts, K.L., & Hall, D.A. (2008). Examining a supramodal network
\nfor conflict processing: A systematic review and novel functional
\nmagnetic resonance imaging data for related visual and auditory
\nStroop tasks. Journal of Cognitive Neuroscience, 20, 1063\u20131078.
\nRobertson, I.H., Manly, T., Andrade, J., Baddeley, B.T., & Yiend, J.
\n(1997). \u2018\u2018Oops!\u2019\u2019: Performance correlates of everyday attentional
\nfailures in traumatic brain injured and normal subjects. Neuropsychologia,
\n35, 747\u2013758.
\nRodriguez-Fornells, A., Rotte, M., Heinze, H.-J., Nosselt, T.M., &
\nMunte, T.F. (2002). Brain potential and functional MRI evidence for
\nhow to handle two languageswith one brain.Nature, 415, 1026\u20131029.
\nRodriguez-Fornells, A., van der Lugt, A., Rotte, M., Britti, B. Heinze,
\nH.J., & Muente, T.F. (2005). Second language interferes with word
\nproduction in fluent bilinguals: Brain potential and Functional imaging
\nevidence. Journal of Cognitive Neuroscience, 17, 422\u2013433.
\nRoelofs, A. (2003). Goal-referenced selection of verbal action: Modeling
\nattentional control in the Stroop task. Psychological Review,
\n110, 88\u2013125.
\nRohrer, D., Salmon, D.P., Wixted, J.T., & Paulsen, J.S. (1999). The
\ndisparate effects of Alzheimer\u2019s disease and Huntington\u2019s disease
\non semantic memory. Neuropsychology, 13, 381\u2013388.
\nRohrer, D.,Wixted, J.T., Salmon, D.P.,& Butters, N. (1995). Retrieval
\nfrom semantic memory and its implications for Alzheimer\u2019s
\ndisease. Journal of Experimental Psychology: Learning, Memory,
\nand Cognition, 21, 1127\u20131139.
\nRosselli, M., Ardila, A., Araujo, K. Weekes, V.A., Caracciolo, V.
\nPadilla, M., & Ostrosky\u2013Solis, F. (2000). Verbal fluency and
\nrepetition skills in healthy older Spanish-English bilinguals.
\nApplied Neuropsychology, 7, 17\u201324.
\nRosselli, M., Ardila, A., Santisi, M.N., Del Rosario Arecco, M.,
\nSalvatierra, A.C., Conde, A., & Lenis, B. (2002). Stroop effect in
\nSpanish-English bilinguals. Journal of the International Neuropsychological
\nSociety, 8, 819\u2013827.
\nSandoval, T.C. (2010). The Role of Control in Bilingual Verbal
\nFluency: Evidence From Aging and Alzheimer\u2019s Disease. Unpublished
\ndoctoral dissertation, University of California, San Diego\/
\nSan Diego State University.
\nSandoval, T.C., Gollan, T.H., Ferreira, V.S., & Salmon, D.P. (2010).
\nWhat causes the bilingual disadvantage in verbal fluency: The
\ndual-task analogy. Bilingualism: Language and Cognition, 13,
\n231\u2013252.
\nSchwartz, A.I., & Kroll, J.F. (2006). Bilingual lexical activation in
\nsentence context. Journal of Memory and Language, 55, 197\u2013212.
\nSchweizer, T.A., Ware, J., Fischer, C., Craik, F.I.M., & Bialystok, E.
\n(2010). Bilingualism as a contributor to cognitive reserve: Evidence
\nfrom computed tomography measurements of medial temporal lobe
\natrophy in dementia. Manuscript submitted for publication.
\nSebastian-Galles, N.,&Bosch, L. (2005). Phonology and bilingualism.
\nIn J.F. Kroll & A.M.B. de Groot (Eds.), Handbook of bilingualism:
\nPsycholinguistic approaches (pp. 68\u201387). New York: Oxford
\nUniversity Press.
\nShadmeher, R., & Holcomb, H.H. (1999). Inhibitory control of competing
\nmotor memories. Experimental Brain Research, 126, 235\u2013251.
\nShin, H.B., & Kominski, R.A. (2010). Language use in the United
\nStates: 2007. Washington, DC: U.S. Department of Commerce
\nEconomics and Statistics Administration, U.S. Census Bureau.
\nSimmonds, D.J., Pekar, J.S., & Mostofsky, S.H. (2008). Meta-analysis
\nof Go\/No go tasks demonstrating that fMRI activation associated
\nwith response inhibition is task dependent. Neuropsychologia,
\n46, 224\u2013232.
\nSpieler, D.H., Balota, D.A., & Faust,M.E. (1996). Stroop performance
\nin healthy younger and older adults and in individuals with
\n128 Bialystok et al.
\n128
\ndementia of the Alzheimer\u2019s type. Journal of Experimental
\nPsychology: Human Perception and Performance, 22, 461\u2013479.
\nStengel, E., & Zelmanowicz, J. (1933). U\u00a8 ber polyglotte motorische
\nAphasie. Zeitschrift fuer die gesamte Neurologie und Psychiatrie,
\n149, 292\u2013311.
\nStern, Y. (2002). What is cognitive reserve Theory and research
\napplication of the reserve concept. Journal of the International
\nNeuropsychological Society, 8, 448\u2013460.
\nStrauss, E., Sherman, E.M.S., & Spreen, O. (2006). A compendium of
\nneuropsychological tests: Administration, norms and commentary.
\nNewYork: Oxford University Press.
\nTreccani, B., Argyri, E., Sorace, A., & Della Sala, S. (2009). Spatial
\nnegative priming in bilingualism. Psychonomic Bulletin & Review,
\n16, 320\u2013327.
\nTzelgov, J., Henik, A., & Leiser, D. (1990). Controlling Stroop interference:
\nEvidence from a bilingual task. Journal of Experimental
\nPsychology: Learning, Memory and Cognition, 16, 760\u2013771.
\nValde\u00b4s, G., & Figueroa, R.A. (1994). Bilingualism and Testing:
\nA Special Case of Bias. Norwood, NJ: Ablex.
\nVan Hell, J.G.,&de Groot, A.M.B. (2008). Sentence context affects lexical
\ndecision and word translation. Acta Psychologica, 128, 431\u2013451.
\nvan Hell, J.G., & Dijkstra, T. (2002). Foreign language knowledge can
\ninfluence native language performance in exclusively native
\ncontexts. Psychonomic Bulletin & Review, 9, 780\u2013789.
\nvan Heuven, W.J.B., Schriefers, H., Dijkstra, T., & Hagoort, P. (2008).
\nLanguage conflict in the bilingual brain. Cerebral Cortex, 18,
\n2706\u20132716.
\nVerhaeghen, P. (2003). Aging and vocabulary scores: A meta\u2013analysis.
\nPsychology and Aging, 18, 332\u2013339.
\nVerhoef, K., Roelofs, A., & Chwilla, D.J. (2009). Role of inhibition in
\nlanguage switching: Evidence from event-related brain potentials
\nin overt picture naming. Cognition, 110, 84\u201399.
\nVerhoef, K.M.W., Roelofs, A., & Chwilla, D.J. (2010). Electrophysiological
\nevidence for endogenous control of attention in switching
\nbetween languages in overt picture naming. Journal of Cognitive
\nNeuroscience, 22, 1832\u20131843.
\nVitevitch, M.S. (2002). The influence of phonological similarity
\nneighborhoods on speech production. Journal of Experimental
\nPsychology: Learning, Memory and Cognition, 28, 735\u2013747.
\nWager, T.D., Jonides, J., & Reading, S. (2004). Neuroimaging
\nstudies of shifting attention: A meta-analysis. Neuroimage, 22,
\n1679\u20131693.
\nWang, Y., Kuhl, P.K., Chen, C., & Dong, Q. (2009). Sustained and
\ntransient language control in the bilingual brain. NeuroImage,
\n47, 414\u2013422.
\nWang, Y.P., Xue, G,M., Chen, C.S., Xue, F.,&Dong, Q. (2007). Neural
\nbases of asymmetric language switching in second-language learners:
\nAn ER-fMRI study. NeuroImage, 35, 862\u2013870.
\nWerker, J.F., & Tees, R.C. (1984). Cross-language speech perception:
\nEvidence for perceptual reorganization during the first year of life.
\nInfant Behavior and Development, 7, 49\u201363.
\nWest, R.L. (1996). An application of prefrontal cortex function theory
\nto cognitive aging. Psychological Bulletin, 120, 272\u2013292.
\nWilliams, Z.M., Bush, G., Rauch, S.L., Cosgrove, G.R., &
\nEskandar, E.N. (2004). Human anterior cingulate neurons and the
\nintegration of monetary reward with motor responses. Nature
\nNeuroscience, 7, 1370\u20131375.
\nWodniecka, Z., Craik, F.I.M., Luo, L., & Bialystok, E. (2010). Does
\nbilingualism help memory Competing effects of verbal ability and
\nexecutive control. International Journal of Bilingual Education
\nand Bilingualism, 13, 575\u2013595.
\nWright, B.C., & Wanley, A. (2003). Adults\u2019 versus children\u2019s performance
\non the Stroop task: Interference and facilitation. British
\nJournal of Psychology, 94, 475\u2013485.
\nYehene, E., Meiran, N., & Soroker, N. (2008). Basal ganglia play a
\nunique role in task switching within the frontal-subcortical circuits:
\nEvidence from patients with focal lesions. Journal of Cognitive
\nNeuroscience, 20, 1079\u20131093.
\nZatorre, R.J. (1989). On the representation of multiple languages in
\nthe brain: Old problems and new directions. Brain and Language,
\n36, 127\u2013147.
\nZelazo, P.D., Frye, D., & Rapus, T. (1996). An age-related dissociation
\nbetween knowing rules and using them. Cognitive Development,
\n11, 37\u201363.
\nZied, K.M., Phillipe, A., Karine, P., Valerie, H-T., Ghislaine, A.,
\nArnaud, R., & Didier, L.G. (2004). Bilingualism and adult differences
\nin inhibitory mechanisms: Evidence from a bilingual stroop
\ntask. Brain and Cognition, 54, 254\u2013256.
\nBilingual Minds 129
\n129