Peer Reviewed Articles Summary (BILINGUALISM AND LANGUAGE DISORDERS IN BILINGUALS) – Students will select two peer reviewed articles (articles are selecte

Peer Reviewed Articles Summary (BILINGUALISM AND LANGUAGE DISORDERS IN BILINGUALS) – Students will select two peer reviewed articles (articles are selecte

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– Students will select two peer reviewed articles (articles are selected and approved below)
– One article will be in bilingualism: 

Bilingualism: consequences for mind and brain

– Second article will be in language disorders in bilinguals

Acquired Language Disorders in Bilinguals 

– Summarize both articles
– Discuss clinical findings relevant to our field
– Provide your personal opinion about the articles

Feature Review

Bilingualism: consequences for mind
and brain
Ellen Bialystok1,2, Fergus I.M. Craik2 and Gigi Luk3

Department of Psychology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada

Rotman Research Institute of Baycrest, 3560 Bathurst Street, Toronto, ON, M6A 2E1,Canada

Harvard Graduate School of Education, 14 Appian Way, Cambridge, MA 02138, USA


Building on earlier evidence showing a beneficial effect
of bilingualism on children’s cognitive development, we
review recent studies using both behavioral and neuro-
imaging methods to examine the effects of bilingualism
on cognition in adulthood and explore possible mecha-
nisms for these effects. This research shows that bilin-
gualism has a somewhat muted effect in adulthood but a
larger role in older age, protecting against cognitive
decline, a concept known as ‘cognitive reserve’. We
discuss recent evidence that bilingualism is associated
with a delay in the onset of symptoms of dementia.
Cognitive reserve is a crucial research area in the context
of an aging population; the possibility that bilingualism
contributes to cognitive reserve is therefore of growing
importance as populations become increasingly diverse.

Why bilingualism?
It is generally believed that more than half of the world’s
population is bilingual [1]. In each of the U.S.A.1 and
Canada2, approximately 20% of the population speaks a
language at home other than English. These figures are
higher in urban areas, rising to about 60% in Los Angeles3

and 50% in Toronto4. In Europe, bilingualism is even more
prevalent: in a recent survey, 56% of the population across all
European Union countries reported being functionally bilin-
gual, with some countries recording particularly high rates,
such as Luxembourg at 99%5. Bilinguals, therefore, make up
a significant portion of the population. Importantly,
accumulating research shows that the development, efficien-

Corresponding author: Bialystok, E. (
1 U. S. Census Bureau (2010) The 2011 Statistical Abstract. Languages Spoken at

Home by Language: 2008, Table 53. Retrieved August 4, 2011 from http://www.census.

2 Statistics Canada (2007) 2006 Census of Canada highlight tables: Population by
language spoken most often at home and age groups, 2006 counts, for Canada, provinces
and territories – 20% sample data. (Catalogue number 97-555-XWE2006002). Retrieved
August 4, 2011 from

3 U. S. Census Bureau (2010) The 2011 Statistical Abstract. Language Spoken at
Home – Cities With 100,000 Persons or More: 2008, Table 55. Retrieved August 4, 2011

4 Statistics Canada (2007) 2006 Census of Canada highlight tables: Population by
language spoken most often at home and age groups, 2006 counts, for Canada, provinces
and territories – 20% sample data. (Catalogue number 97-555-XWE2006002). Retrieved
August 4, 2011 from

5 European Commission (2006) ‘Special Eurobarometer 243: Europeans and their
Languages (Executive Summary)’ (PDF). Europa web portal. p. 3. Retrieved Novem-
ber 1, 2011 from

240 1364-6613/$ – see front matter � 2012 Elsevier Ltd. All rights reserv

cy, and decline of crucial cognitive abilities are different for
bilinguals than for monolinguals. What are these cognitive
differences and how does bilingualism lead to these changes?

The context for examining how bilingualism affects cog-
nitive ability is functional neuroplasticity, that is, the study
of how experience modifies brain structure and brain func-
tion. Such modifications have been found following experi-
ences as diverse as juggling [2], video-game playing [3],
careers in architecture [4], taxi-driving [5], and musical
training [6,7]. Bilingualism is different from all of these:
like juggling and playing video games, it is intense, and, like
architecture and driving taxis in London, it is sustained, but,
unlike these experiences, bilinguals are not typically pre-
selected for talent or interest. Although bilinguals undoubt-
edly differ from monolinguals in certain ways, they gener-
ally did not choose bilingualism. Rather, the circumstances
of their family, place of birth, or immigration history simply
required that they learn more than one language.

What is different about bilingual minds?
It has long been assumed that childhood bilingualism
affected developing minds, but the belief was that the
consequences for children were negative: learning two
languages would be confusing [8]. A study by Peal and
Lambert [9] cast doubt on this belief by reporting that
children in Montreal who were either French-speaking
monolinguals or English–French bilinguals performed dif-
ferently on a battery of tests. The authors had expected to
find lower scores in the bilingual group on language tasks
but equivalent scores in non-verbal spatial tasks, but
instead found that the bilingual children were superior
on most tests, especially those requiring symbol manipu-
lation and reorganization. This unexpected difference be-
tween monolingual and bilingual children was later
explored in studies showing a significant advantage for
bilingual children in their ability to solve linguistic prob-
lems based on understanding such concepts as the differ-
ence between form and meaning, that is, metalinguistic
awareness [10–16] and non-verbal problems that required
participants to ignore misleading information [17,18].

Research with adult bilinguals built on these studies with
children and reported two major trends. First, a large body
of evidence now demonstrates that the verbal skills of
bilinguals in each language are generally weaker than
are those for monolingual speakers of each language.

ed. doi:10.1016/j.tics.2012.03.001 Trends in Cognitive Sciences, April 2012, Vol. 16, No. 4

Review Trends in Cognitive Sciences April 2012, Vol. 16, No. 4

Considering simply receptive vocabulary size, bilingual
children [19] and adults [20] control a smaller vocabulary
in the language of the community than do their monolingual
counterparts. On picture-naming tasks, bilingual partici-
pants are slower [21–24] and less accurate [25,26] than
monolinguals. Slower responses for bilinguals are also found
for both comprehending [27] and producing words [28], even
when bilinguals respond in their first and dominant lan-
guage. Finally, verbal fluency tasks are a common neuro-
psychological measure of brain functioning in which
participants are asked to generate as many words as they
can in 60 s that conform to a phonological or semantic cue.
Performance on these tasks reveals systematic deficits for
bilingual participants, particularly in semantic fluency con-
ditions [29–33], even if responses can be provided in either
language [34]. Thus, the simple act of retrieving a common
word is more effortful for bilinguals.

In contrast to this pattern, bilinguals at all ages demon-
strate better executive control than monolinguals matched in
age and other background factors. Executive control is the set
of cognitive skills based on limited cognitive resources for
such functions as inhibition, switching attention, and work-
ing memory [35]. Executive control emerges late in develop-
ment and declines early in aging, and supports such activities
as high-level thought, multi-tasking, and sustained atten-
tion. The neuronal networks responsible for executive control
are centered in the frontal lobes, with connections to other
brain regions as necessary for specific tasks. In children,
executive control is central to academic achievement [36],
and, in turn, academic success is a significantpredictor of long
term health and well being [37]. In a recent meta-analysis,
Adesope et al. [38] calculated medium to large effect sizes for
the executive control advantages in bilingual children, and
Hilchey and Klein [39] summarized the bilingual advantage
over a large number of studies with adults. This advantage
has been shown to extend into older age and protect against
cognitive decline [21,40,41], a point to which we turn below.

In this review, we examine the evidence for bilingual
advantages in executive control and explore the possible
mechanisms and neural correlates that may help to ex-
plain them. Our conclusion is that lifelong experience in
managing attention to two languages reorganizes specific
brain networks, creating a more effective basis for execu-
tive control and sustaining better cognitive performance
throughout the lifespan.

Language processing in bilinguals
Joint activation of languages

A logical possibility for the organization of a bilingual mind
is that it consists of two independently-represented lan-
guage systems that are uniquely accessed in response to
the context: a fluent French–English bilingual ordering
coffee in a Parisian café has no reason to consider how to
form the request in English, and a Cantonese–English
bilingual studying psychology in Boston does not need to
recast the material through Chinese. Yet, substantial evi-
dence shows that this is not how the bilingual mind is
organized. Instead, fluent bilinguals show some measure of
activation of both languages and some interaction between
them at all times, even in contexts that are entirely driven
by only one of the languages.

The evidence for this conclusion comes from psycholin-
guistic studies using such tasks as cross-language priming
(in which a word in one language facilitates retrieval of a
semantically related word in the other language) and
lexical decision (in which participants decide whether a
string of letters is an actual word in one of the languages)
that show the influence of the currently unused language
for both comprehension and production of speech [42–48].
Further evidence comes from patient studies showing
intrusions from the irrelevant language or inappropriate
language switches [49], and imaging studies indicating
involvement of the non-target language while performing
a linguistic task in the selected language [50–52]. Using
eye-tracking technology, for example, Marian, Spivey, and
Hirsch [53] reported that English–Russian bilinguals per-
forming a task in English in which they had to look at the
named picture from four alternatives were distracted by a
picture the name of which shared phonology with Russian,
even though there was no connection to the meaning of the
target picture and no contextual cues indicating that Rus-
sian was relevant. Similarly, Thierry and Wu [54] pre-
sented English monolinguals, Chinese–English bilinguals,
and Chinese monolinguals with pairs of words in English
(translated to Chinese for Chinese monolinguals) and
asked participants to decide if the words were semantically
related or not. The manipulation was that half of the pairs
contained a repeated character in the written Chinese
forms, even though that orthographic feature was unrelat-
ed to the English meaning. Waveforms derived from anal-
yses of electroencephalography (EEG) are used to indicate
the neuronal response to language on a millisecond by
millisecond scale. An event-related potential (ERP) called
the N400 (i.e. a negative-going waveform peaking approxi-
mately 400 msec after the onset of a target stimulus)
signals the effort associated with integrating the meaning
of words. The more similar the words are to each other, the
smaller is the amplitude of the N400. In the study by
Thierry and Wu, semantic relatedness was associated with
significantly smaller N400 amplitude in all groups as
expected, but the repeated character also led to smaller
N400 for the two Chinese groups. Thus, although irrele-
vant to the task, participants were accessing the Chinese
forms when making judgments about the semantic relation
between English words. Subsequent research has refined
these results by showing their basis in the phonology
rather than the orthography of spoken language [55]
and extended the phenomenon to the phonological hand
forms of American Sign Language [56].

This joint activation is the most likely mechanism for
understanding the consequences of bilingualism for both
linguistic and non-linguistic processing. For linguistic pro-
cessing, joint activation creates an attention problem that
does not exist for monolinguals: in addition to selection
constraints on such dimensions as register, collocation, and
synonymy, the bilingual speaker also has to select the
correct language from competing options. Although joint
activation creates a risk for language interference and
language errors, these rarely occur, indicating that the
selection of the target language occurs with great accuracy.
However, this need to select at the level of language system
makes ordinary linguistic processing more effortful for


Review Trends in Cognitive Sciences April 2012, Vol. 16, No. 4

bilinguals than monolinguals and explains some of the
costs in psycholinguistic studies described above. For
non-linguistic processing, the need to resolve competition
and direct attention is primarily the responsibility of gen-
eral cognitive systems, in particular executive functions.
The possible influence of linguistic processes on non-lin-
guistic executive control has significant consequences for
lifespan cognition and is discussed in the next section.

Consequences of joint activation

An appealing suggestion for how the executive control
system achieves linguistic selection in the context of joint
activation is through inhibition of the non-target language.
At least two influential models have been proposed that
place inhibition at the center of this selection. The first, the
Inhibitory Control model [57] is based on the Supervisory
Attentional System [58] and extends a domain-general and
resource-limited attention system to the management of
competing languages. The second, the Bilingual Interac-
tive Activation Model (BIA+) [59], uses computer simula-
tion to model lexical selection from both intralingual and
extralingual competitors. Although both models assign a
primary role to inhibition, they are very different from each
other and address a different aspect of the selection prob-
lem. It is useful, therefore, to consider the distinction
between global inhibition and local inhibition proposed
by De Groot and Christoffels [60]. Global inhibition refers
to suppression of an entire language system, as in inhibit-
ing French when speaking English, and local inhibition
refers to inhibition of a specific competing distractor, such
as the translation equivalent of the required concept. Both
processes are required for fluent language selection but the
two are carried out differently. Guo, Liu, Misra, and Kroll
[61] used functional magnetic resonance imaging (fMRI) to
demonstrate the recruitment of different systems for each
of global inhibition (dorsal left frontal gyrus and parietal
cortex) and local inhibition (dorsal anterior cingulate cor-
tex, supplementary motor area) in a sample of Chinese–
English bilinguals, and validated their distinct roles in
bilingual language control. Although Green’s inhibitory
control model is consistent with both types of inhibition,
Dijkstra’s BIA+ model is limited to modeling item selection
in local inhibition.

These types of inhibition also differ in their primary
domain of influence, with local inhibition largely affecting
linguistic performance and global inhibition affecting both
linguistic and cognitive performance. The linguistic out-
comes of inhibition are reduced speed and fluency of lexical
access for bilinguals as described above. However, perfor-
mance also requires a selection bias towards the target
language, showing a role for activation [62,63] as well as
inhibition. These alternatives are not mutually exclusive
but indicate the need for a more complete description of
how attention is managed in bilingual language proces-
sing. Ultimately the degree of both inhibition and activa-
tion are relative rather than absolute and will be
modulated by contextual, linguistic, and cognitive factors.
The cognitive outcomes of linguistic inhibition are en-
hanced attentional control and will be described more fully
in the next section. Importantly, the cognitive and linguis-
tic outcomes are related. Three studies have reported a


relationship between inhibition and ability in verbal and
non-verbal tasks by showing a correlation between Stroop
task performance and competing word selection [64], Si-
mon task performance and language switching in picture
naming [65], and cross-language interference and a variety
of executive control measures [66]. Such results point to an
extensive reorganization of cognitive and linguistic pro-
cesses in bilinguals.

Cognitive networks in bilinguals
Bilingual performance on conflict tasks

Early evidence that bilingual children solved non-verbal
conflict tasks differently from monolingual children was
reported in a study by Bialystok and Majumder [17]. Eight-
year-old children were given a variety of non-verbal
problems to solve, some of which contained perceptual
distraction (block design from the Wechsler Intelligence
Scale for Children, WISC [67]) and some which did not
(Noelting’s Juice Task [68,69]). Bilingual children outper-
formed monolinguals on the conflict tasks, but children in
the two groups were comparable on tasks that did not
include distracting perceptual information. This pattern
has been confirmed in studies of both children and adults
using a flanker task (children: [70,71]), theory of mind task
(children: [72,73]; adults: [74]), Simon task (children: [75];
adults: [40]). Other studies with adults have shown better
performance by bilinguals in naming the font color in a
Stroop task [21], smaller costs in task switching [76], better
ability to maintain task set in an attention task [77], and
more susceptibility to negative priming, presumably be-
cause of greater inhibition [78].

Some studies have extended these bilingual advantages
into older age. Bialystok, Craik, Klein and Viswanathan
[40] reported an experiment in which middle-aged and
older adults who were either monolingual or bilingual were
given a version of the Simon task. Participants were shown
either a green or a red square on each trial, and the task
was to press an associated response key as rapidly as
possible. The keys were located at each side of the presen-
tation screen. In one condition, the squares appeared
centrally on the screen, so there was no spatial conflict
between the location of stimuli and responses; in this
condition there were no reaction-time (RT) differences
between language groups. In a second condition, the col-
ored squares appeared laterally on the screen, either di-
rectly above the appropriate response key (congruent
condition) or on the other side of the screen, above the
incorrect response key (incongruent condition). The RT
difference between congruent and incongruent response
trials (the Simon effect) is a measure of attentional control.
Bilinguals produced smaller Simon effects than monolin-
guals at all ages.

Three other results from this study are noteworthy.
First, the decrease in attentional control in older adults
was reduced in the bilingual groups, suggesting that bilin-
gualism may be protective against the effects of cognitive
aging. Second, whereas a bilingual advantage was
expected for incongruent stimuli, it was also found for
congruent stimuli. This result has been replicated in sub-
sequent studies [39] and is difficult to account for in terms
of response conflict or inhibition. Third, prolonged practice

Review Trends in Cognitive Sciences April 2012, Vol. 16, No. 4

reduced both the Simon effect and the size of the bilingual
advantage. Apparently all participants can learn to disre-
gard the distracting effects of interfering stimuli given
sufficient practice on a task, but it seems that bilinguals
can learn this type of inhibition more rapidly. One inter-
esting question in this regard is the extent to which this
attenuation of attentional control is specific to the prac-
ticed situation, or whether it generalizes to tasks tapping
attentional control in a different manner. Our conjecture is
that the attenuation effect is context specific.

A complication that has emerged as more results are
reported is that the bilingual advantage is not always
found in samples of young adults. For example, a study
examining performance on the Simon task in 5-year-olds,
young, middle-aged and older adults found a bilingual
advantage in RT in the 5-year-olds and in the older adults,
but not in the young adult group [79]. Similarly, a study of
the Stroop effect in younger and older adults found a
bilingual advantage in both age groups but when the same
participants performed the Simon arrow task the bilingual
advantage was found only in the older adults [21]. Simi-
larly, Salvatierra and Rosselli [41] used a simple version of
the Simon task and reported a bilingual advantage for
older but not younger adults. There is thus some evidence
that the bilingual advantage is greatest in children and in
older adults, but less constantly present in young adults –
perhaps because the young adult group is at the develop-
mentally peak age for cognitive control.

It appears that bilingual advantages for young adults
tend to emerge on tasks or conditions that are difficult. For
example, Bialystok [80] found that bilingual young adults
outperformed their monolingual counterparts on the direc-
tional arrow Simon task, but only on the condition that
included more monitoring and switching than a simpler
condition. Similarly, several studies by Costa and collea-
gues have reported a bilingual advantage in young adults
[71,81,82] but only under some conditions. For example,
Costa et al. [81] demonstrated that the bilingual advantage
on a flanker task held only under high monitoring condi-
tions. In versions where most of the trials were of one type
(congruent or incongruent), no bilingual advantage was
observed; the advantage was found, however, in a condition
involving 25% incongruent and 75% congruent trials, al-
though even there the advantage decreased over blocks of
the experiment (cf. [44]). Costa et al. [81] concluded that the
bilingual advantage reflects a more efficient monitoring
system for conflict resolution, in that bilinguals may be
better at determining when the misleading information
can be safely ignored. Finally, Hernández et al. [82] used a
non-linguistic version of the Stroop effect and found a trend
towards both reduced interference and enhanced facilita-
tion in young adult bilinguals compared with monolinguals
(cf. older participants in [21]). One interesting aspect of the
studies by Costa, Hernández and colleagues is that the
monolinguals were Spanish speakers and the bilinguals’
two languages were Catalan and Spanish. Most of the
participants were undergraduate students and were not
immigrants, so the two groups were well equated apart
from the language difference. In summary, the evidence for
a bilingual advantage in younger adults is more sporadic
than in other age groups, although at all ages there are

some reports of studies showing no difference between
monolinguals and bilinguals performing a conflict task.

Neural correlates of cognitive reorganization

Recently, studies have begun to investigate the neural
correlates of bilingual processing examined in the behav-
ioral research. The majority of this research has used fMRI
to study bilinguals performing a linguistic task in their two
languages. Typically, participants name pictures or gener-
ate words in response to a cue signaling the required
language, and performance is compared for single lan-
guage and mixed language conditions. Two early studies
revealed promising results. The first led to the surprising
finding that language switching was accompanied by acti-
vation in the dorsolateral prefrontal cortex (DLPFC), an
area known to be part of the general executive control
system [24]. Less surprising was a study showing the
involvement of Broca’s area as well as a left frontal
area in a language switching task [83]. Subsequent re-
search has corroborated the involvement of these systems
and has shown that language switching elicits a spatially-
distributed activation pattern involving bilateral frontal
and precentral areas, bilateral caudate, bilateral (or mid-
line) pre-supplementary areas (pre-SMA), and bilateral
temporal regions. This pattern has been found for Ger-
man-French bilinguals [84], Spanish-Catalan bilinguals
[85], Chinese–English bilinguals [61,86,87] and Span-
ish–English bilinguals [88]. A few studies [61,84] have also
reported activation in anterior cingulate cortex (ACC), but
activation in this area is not consistently observed. Abu-
talebi and colleagues [89] extended this finding to show
activation of ACC for both language switching and non-
verbal switching. Importantly, these studies confirm that
frontal systems involved in executive control are recruited
by bilinguals to manage attention to language.

Abutalebi and Green [90] conducted a qualitative review
of these studies and proposed that the ACC, left prefrontal
cortex, left caudate and bilateral supramarginal gyri (SMG)
constitute the neural correlates of the control mechanism for
bilingual language production. This model was confirmed in
a quantitative meta-analysis examining bilingual language
switching [91] (Figure 1). Both the qualitative and quanti-
tative analyses point to multiple cortical regions in which
functional activity is altered by bilingualism, but an out-
standing question is whether activity in these regions is
synchronous, forming a neural network that is responsive to
bilinguals’ experience of managing two languages. To this
end, a study by Nakamura and colleagues [92] showed
strong connectivity between left inferior frontal gyrus
(IFG) and left middle temporal gyrus (MTG) in a group of
Japanese–English bilinguals performing a cross-language
priming task. The connectivity was stronger in the frontal-
temporal coupling than in the reverse direction. This pat-
tern was replicated using transcranial magnetic stimulation
(TMS) with Japanese–English bilingual participants per-
forming the same cross-language priming task. Nakamura
and colleagues [92] interpreted the results as indicating top-
down control from left IFG to left MTG in a bilingual context.

Taken together, fMRI research on bilingual language
switching has implicated distributed cortical activation
that converges in the frontal regions. Intriguingly, the


Left Right

TRENDS in Cognitive Sciences

Figure 1. Bilingual influence on brain function and structure. Transparent brains showing the left and right hemispheres. Green voxels depict grey matter regions showing

high activation during bilingual language switching in a meta-analysis [90]. Red–yellow voxels indicate regions of higher white matter integrity in bilingual older adults

relative to monolinguals [107]. Together, the functional and structural data indicate that neural correlates of bilingualism are observed in the frontal lobes, generally

responsible for higher cognition such as executive functions.

Review Trends in Cognitive Sciences April 2012, Vol. 16, No. 4

brain regions related to bilingual switching are also critical
for general attention and cognitive control [93,94]. This
overlap in brain regions activated for bilingual switching
and cognitive control implies that the same mechanisms
may be involved in both activities, and that these shared
processes might help to explain the superior performance
of bilinguals on non-verbal conflict tasks. In other words,
using these cognitive control networks for bilingual lan-
guage processing may reconfigure them for other purposes,
providing part of the explanation for the behavioral differ-
ences between monolinguals and bilinguals found in non-
verbal conflict tasks. Specifically, the evidence suggests
that cognitive control networks may be more broadly based
in bilinguals as a result of their dual func

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