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Cognitive Flexibility of Bilingualism
Mary Jolly
University of Lisbon
2012
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Cognitive Flexibility of Bilingualism
Introduction
This is a discussion of the phenomenon of bilingualism and its implications on
cognition. Monolingual and bilingual speakers follow the same general course of language
acquisition and development – both groups learn phonemes and discover grammar, however,
experimental data indicate that the ways in which bilingual and monolingual acquisition and
further linguistic development happen differ. The research challenge is to identify and
interpret these differences.
Bilingualism and its characteristics
There is a vast diversity among people who speak more than one language in regard
to whether the acquisition of two or more languages was simultaneous, the age when they
acquired both languages, the frequency of daily usage of languages, and the extent of
proficiency. There is no consensus among researchers on what exactly constitutes personal
bilingualism, and its definitions range from just the ability to speak two languages to the
condition of acquiring two languages simultaneously at an early age. For example, Grosjean
(1999) defines bilingualism as “the use of two languages in one's everyday life and not
knowing two or more languages equally well and optimally.” Gottardo & Grant (2008)
refrain from an exact definition and instead suggest that “bilingualism should be thought of as
being on a continuum, where one can have varying levels of proficiency in two languages”.
For the purpose of this discussion bilingual individuals are defined as those who
acquired two languages simultaneously in early childhood and whose usage of both
languages has been ongoing.
Based on the variety of conditions under which the knowledge of two languages is
acquired, the following theoretical classification of the types of bilingualism was proposed:
compound, coordinate, and sub-coordinate (D’Acierno, 1990). Compound bilingualism refers
to the situation when a person learns two languages in the same environment; for example,
when one’s parents speak two languages at home. In this case, the bilingual person has one
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set of meaning units with two modes of expression (one signified for two signifiers) and
neither language dominates.
Coordinate bilingualism occurs when two languages are learned in two different
environments as, for example, in home and school contexts; such bilingual individual has two
separate independent language systems or two sets of meaning units and two ways of
expression (two signifiers and two signifieds for each word). The third type, sub-coordinate
bilingualism presupposes dominance of one language, which happens when a person uses the
same language at home and at school but communicates in other contexts in another
language. In this case, meaning units belong to the dominant language and the person uses
two forms of expressions.
Another categorization of bilinguals is based on the timing of the acquisition of two
languages and distinguishes between early and late bilingualism. There is no consensus on
the exact age of early acquisition: ages from the first month of life to ten or twelve years old
can define early bilingualism. However, most researchers agree on the timing of late
bilingualism, which refers to the acquisition of a second language after the critical/sensitive
period for language learning.
Pinker (1994) supported the notion of critical period for specific learning saying that
“…acquisition of a normal language is guaranteed for children up to the age of six, is steadily
compromised from then until shortly after puberty, and is rare thereafter” (p. 298). He
attributed the closing window in language development to the changes in the maturing brain –
neural pruning and decrease of metabolic rate. Applied to bilingualism, the critical period
translates into a loss of ability to master the phonology of a second language after puberty.
Studies that tested immigrant children in the US confirmed that late bilinguals can become
highly proficient in a second language in terms of grammar and vocabulary but always retain
a foreign accent (Newport, 1990).
Most reaseachers agree that Chomsky’s nativist theory is fully applicable as a
theoretical framework for the study of bilingualism, since empirical data indicate that “human
mind is as prepared to acquire two first languages as it is to acquire one” (Werker & ByersHeinlein, 2008) and that the acquisition of two or one languages follows largely the same
pattern (Werker, Byers-Heinlein, & Fennell, 2009). During the course of language acquisition
bilingual children show identical tendencies, namely innate mechanisms of the language
acquisition device that require environmental triggers to bring about linguistic development
(Chomsky, 1968).
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Several models of bilingualism have been proposed; for example, the subset
hypothesis (Paradis, 2007) suggests the existence of a two-level bilingual cognitive system.
The first is an extended structure and stores both languages in identical ways; the second
level is a substructure containing separate networks of connections between the elements of
each language. Other bilingualism hypotheses refer to the existence of two separate lexicons,
a language switch that keeps the two languages separate, and the role of inhibition and
attention in language discrimination. So far, there has been no agreement between researchers
on the most viable hypothesis and the existing models have not been convincingly tested by
experiments.
Experimental research on bilingualism
Methodology of most studies involves a comparison between bilingual and
monolingual people; even though Grosjean justly stated that “the bilingual is a unique
speaker-hearer who should be studied as such and not always in comparison with the
monolingual” (1999). Studies on bilingual acquisition often involve infant participants as it is
thought that bilingual language acquisition begins at birth or even before.
Bilingualism is closely related to multilingualism; however, most studies are carried
out with participants who use two languages. While there are many people who master three
and more languages, they differ from bilinguals in that early bilingualism normally comes
about in a natural way, due to the child’s life circumstances, while trilingualism or
multilingualism is often a result of intentional learning and thus is a matter of choice
(Bialystok, 2011). The intentionality of acquisition would add additional variables to the
experiment as, for example, level of education, intelligence, or personal interests and could
skew the results; therefore, a direct comparison of two types of natural language acquisition
is deemed the most effective method of study.
Research has provided empirical support to the assertion that the same fundamental
principles operate in bilingual and monolingual language acquisition. For example, Werker &
Byers-Heinlein (2008) found that a single architecture supports the acquisition of two
languages simultaneously; Mattock & Burnham (1988) concluded that monolingual and
bilingual speakers go through similar language development milestones; Byers-Heinlein,
Burns, & Werker (2010) confirmed that the same perceptual and learning mechanisms that
support monolingual acquisition support a bilingual one; and Werker, Byers-Heinlein, &
Fennell (2009) demonstrated that on basic word-learning tasks, monolinguals and bilinguals
show identical abilities.
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It appears that similarities in bilingual and monolingual acquisition refer to the macrolevel and differences have been observed at micro-level of language development.
Experimental data have shown some differences between bilingual and monolingual speakers
in areas of cognition, linguistics, and neurophysiology. For example, in cognitive terms,
bilinguals show a superior ability of divergent thinking, enhanced metacognitive skills and a
higher capacity to inhibit irrelevant stimuli. Bilinguals also show processing advantage in the
ability to solve problems containing confusing perceptual information (Bialystok, 2010).
In linguistic terms, bilinguals have been observed to develop an understanding of taxonomic
relationships earlier than monolinguals. In the area of neurophysiology, bilinguals’ brain
shows a higher degree of bilateral processing in both language and nonverbal activity
(Housman et al., 2004).
Common preference in infancy for the mother tongue accounts for both bilingual and
monolingual infants’ listening attention to their language, but the difference is that a
monolingual directs attention to a single language while a bilingual pays attention to two
languages (Byers-Heinlein, Burns, & Werker, 2010).
Current research has studied such categories as language discrimination and
separation, speech perception, phonetic development, word recognition, word learning, and
conceptual development, to name just a few. The task to distinguish between two languages
is the point where monolingual and bilingual language acquisition paths diverge - bilingual
infants start building representations of sounds and words for each of the two languages
(Werker & Byers-Heinlein, 2008). Through studies with preverbal bilingual infants, it has
been established that infants cope with this task by applying phonetic sensitivities to word
learning (Werker, Byers-Heinlein, & Fennell, 2009). In other words, they use acoustic
information to discriminate between their two languages. It seems that phonetic sensitivity at
the beginning of life ensures bilingual flawless mastery of the sound patterns of both
languages – mastery that later becomes progressively difficult to achieve as the brain
matures.
In adult bilinguals congnitive mechanisms ensure language discrimination. It has been
established that both languages are active in bilingual speakers’ minds during their
monolingual mode, so the question arises about the mechanisms that keep the two languages
from interfering with each other. In Bialystok’s opinion the executive control system in the
frontal and prefrontal cortex is in charge of focusing attention on one language (2011).
At times, studies show contradictory outcomes of the comparison of monolingual and
bilingual infants’ performance on similar tasks. For example, some researchers found that
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bilinguals manage the word learning tasks that require the application of phonetic sensitivities
at a later age than monolinguals (Fennell et al., 2007; Ramon-Casas et al., 2009), however,
others observed a superior performance by bilinguals (Mattock et al., 2008). Some authors
hypothesize that bilinguals may indeed master some language developmental tasks at a later
age than monolinguals because they may have a delay in forming stable phonological
representations due to their experience of a significantly larger phonetic variability. Another
explanation of the delay may be greater processing demands imposed by the need to separate
two languages.
Kuhl (2005) explains the observed delay using the notion of neural commitment,
which refers to brain’s capacity to wire itself to understand one language and its sounds. Her
study with electroencephalogram showed that 6-month old monolingual infants could
discriminate between phonetic sounds of any language but by 12 months this ability
disappeared and they recognized only the language they normally heard. The bilingual infants
demonstrated a different developmental course: at 6 months they did not detect phonetic
differences in either language but by 12 months they could discriminate sounds in both
languages. The author concluded that bilingual infants showed a delay in perceptual
narrowing because the variability in their experience kept their phonetic perception open,
which confirms the view that experience shapes the brain.
Interesting results emerged from research on the use of word learning heuristics,
specifically disambiguation heuristic, which refers to the tendency of infants by the age of 17
months to associate a novel noun with a novel object rather than a familiar one. ByersHeinlein & Werker (2009) observed strong use of this heuristic by monolingual infants,
marginal use by bilinguals, and no disambiguation use by trilinguals. Intriguingly, it was not
the vocabulary size that predicted performance but the number of languages learned. The
authors concluded that a particular language experience plays a role in the development of
disambiguation.
The issue of inhibition is another focus in bilingualism research. According to the
inhibitory control model (Green, 1998), bilinguals employ multiple levels of control of their
two languages and use language tags to discriminate between them. Experimental data show
that bilinguals have better inhibitory control for ignoring irrelevant perceptual information.
Bialystok & Martin (2004) reported that in their experiment with card sorting task, bilingual
preschool children demonstrated a better control of attention by selectively directing attention
to specific aspects of representation; this ability proved advantageous in problem solving
tasks that required intentional focus on some information and the exclusion of other stimuli.
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Recent advances in technology contributed to the development of the neurolinguistics
of bilingualism through widespread use of neuroimaging methods. Neuroscientific studies
have detected some structural and functional brain differences between bilinguals and
monolinguals. For example, in one study adult participants completed a syntactic sentencejudgment task during functional magnetic resonance imaging (fMRI); while both
monolinguals and bilinguals showed predicted increases in activation in classic language
areas, bilinguals had a significantly greater increase in the blood oxygenation level-dependent
signal (BOLD) in the left inferior frontal cortex when processing English than the English
monolinguals (Kovelman, Baker, & Petitto, 2008). This outcome indicates that cognitive
processes may vary between the two categories of speakers and led the authors to speculate
about a possible existence of a “neural signature” of bilingualism. Other neuroimaging
studies support the importance of the timing of the first bilingual exposure not only for
mastery of languages but also for further cognitive development. Petitto (2009) found that
early bilingualism predicts reading mastery.
Experiments with adult participants have demonstrated long-term effects of early
exposure to two languages. For example, fMRI studies revealed greater gray matter density in
left hemisphere regions of bilingual adults (see Appendix 1). In cognitive terms, the
inhibitory control in older bilinguals is slower to decline with age and their average age of
dementia onset is later; linguistically, bilingual adults demonstrated a better ability to learn
new words (Marian et al, 2009).
Generally, the left cerebral hemisphere is considered to be specialized for most
language functions (Damasio, 1994) and monolinguals and late bilinguals follow this
lateralization pattern. However, hemisphere lateralization appears to be somewhat different in
early bilinguals’ brains which show a consistent bilateral processing of language (Hull &
Vaid, 2007). This finding indicates that early experience with a single language fixes the left
hemisphere dominance in language processing; conversely, early bilingual exposure recruits
bilateral processing mechanisms, and both patterns are durable and transfer into adulthood.
Cognitive flexibility in bilingualism
The analysis of the empirical data obtained so far suggests an enhanced cognitive
flexibility of bilinguals. Bilinguals, when compared to monolinguals, seem to have a better
ability to understand the structure and the meaning of language. Bialystok has studied
metalinguistic development of children between the ages of five and nine; in her experiments
she asked the participants to evaluate grammatical correctness of a nonsensical sentence (for
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example, "Apples grow on noses.") and found that bilingual children were more accurate in
their judgment. The author attributed this outcome to the bilinguals’ rich experience in
“resolving the conflict between form and meaning” (2011).
The bilinguals’ cognitive advantages seem to continue throughout life. Repeated
studies with patients diagnosed with Alzheimer's disease showed that within the group of the
same age and same cognitive level, the bilingual patients had considerably more damage in
the medial-temporal cortex than the monolinguals. This meant that the bilingual patients’
disease was much more advanced, however, their cognitive functioning was at the same level
than that of a less advanced monolingual patients. The author concluded that cognitive
enhancement of bilinguals helped them cope with the disease better (Bialystok, 2011). Thus,
a life-long experience of using two languages may cause reconfiguration of the brain
networks which provides evidence for cognitive plasticity of the human brain. Neuroimaging
studies corroborated protective effects of bilingualism on behavioral symptoms of dementia.
For example, Sanjuan (2010) suggested a neurobiological explanation that an increased
synaptic density that results from additional learning provides a greater redundancy in brain
mechanisms which, in turn, compensates for cognitive losses.
Conclusion
Recent research in bilingualism has acknowledged that universal patterns of language
acquisition and development apply to both monolingual and bilingual speakers; however, it
has also indicated differences in particular cognitive processes between them. Early bilingual
language acquisition appears to impart durable cognitive advantages on individuals, such as
enhanced metalinguistic awareness, strengthened executive control system, and cognitive
flexibility. Researchers suggest that bilingualism also contributes to the delay of age-related
cognitive decline. Neuroimaging studies indicate that early bilingualism changes brain
structure which is in agreement with the view of brain plasticity. Currently, specific ways of
language-related brain organization of bilinguals can be only hypothesized and further
research is imperative. Ongoing behavioral and neuroimaging studies promise to elucidate the
phenomenon of bilingualism.
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Appendix 1
Source: Society for Neuroscience, 2008
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