Bilingualism and cognitive control
The ability to switch between different languages is an interesting
phenomenon in bilingual speakers given that different languages partially
share neuro-anatomical representations (Klein, Milner, Zatorre, Zhao, &
Nikelski, (1999). Producing a word in a particular language activates a
conceptual system and not only the lexical representation of the word in
the target language but also the lexical representation in the non-target
language. Not only are the lexical representations of the non-target
language activated, but also the phonological properties of the word. To
select a word should give rise to interference between these
representations and it has been suggested that selection of the correct
word is made possible through cognitive control processes. (RodriguezFornells, De Diego Balaguer, & Münte, 2006).
Cognitive control processes enables goal-oriented behaviour through
constraint of thoughts and responses, witch include controlled retrieval of
relevant information from long-term memory, inhibition of irrelevant
responses, selection of relevant responses, ability to handle competing
representations and task-switching. Prefrontal cortex is crucial to
cognitive control (Wagner, Bunge, & Badre, 2004).
Language switching
Effects of interference between competing language schemes has been
demonstrated in task-switching experiments. Meuter and Allport (1999)
let bilinguals name numerals in either their first or second language.
Digits were presented with a frame indicating witch language they should
use in naming. The different frames appeared unpredictably and
response latencies (RTs) where measured during switching between
naming in the different languages. As expected, switching between L1
and L2 gave rise to longer RTs compared to non-switching trials. On
switching trials, switching from the less dominant L2 to the more
dominant L1 was associated with longer RTs compared to switching from
L1 to L2. A possible interpretation of the results is that naming in the less
dominant L2 requires active inhibition of the more dominant L1. During
language switching, reactivation of the more dominant language takes
more time because suppression of L1 is more demanding than
suppression of L2.
Language selection and inhibition
According to Green’s Inhibitory Control model (1998) are different
languages represented by different language schemes and usage of one
language involves inhibitory control over the interfering non-target
language. A competing language scheme must be inhibited in selection
of a target language and switching between languages will according to
the model require more cognitive capacity. The model is based on the
supervisory attention system, described by Shallice and Burgess, and
Green suggests that the inhibitory mechanism underlying lexicosemantic control is a general cognitive mechanism and not specific to
language processes.
Effects on cognitive control
Ellen Bialystok has in couple of experiments demonstrated not only that
cognitive control may be involved in bilingual language processing, but
also that bilingualism can enhance cognitive control processing.
Inhibitory control in bilinguals has been investigated in non-verbal tests
traditionally
performances
used
to
measure
in
these
tests
executive
are
usually
functions.
better
Bilinguals
compared
to
monolinguals. In one study magneto-encephalography (MEG) was used
to investigate the neural correlates of bilinguals and monolinguals
performances on the Simon Task (Bialystok, Craik, Grady, Chau, Ishii,
Gunji, & Pantev, 2005). Red and green squares where presented on a
screen and the participants where instructed to press response keys with
the left or the right hand depending on the colour of the square. The
squares where presented to the right or to the left on the screen and the
participants had to concentrate on the colour and ignore the irrelevant
position of the squares. Faster reaction time in the bilingual group
correlated with greater activity in superior/middle temporal regions,
cingulate and superior/inferior frontal regions, mostly in the left
hemisphere. Faster reaction time in monolinguals correlated with
enhanced activity in middle frontal regions. It was suggested that
bilingualism lead to systematic changes in executive functions in frontal
regions.
References
Bialystok, E., Craik, F. I. M., Grady, C., Chau, W., Ishii, R., Gunji, A., &
Pantev, C. (2005). Effects of bilingualism on cognitive control in the
Simon task: evidence from MEG. Neuroimage, 40-49.
Green, D. W. (1998). Mental control of the bilingual lexico-samantic
system. Bilingualism: Language and Cognition, 67-81.
Klein, D., Milner, B., Zatorre, R. J., Zhao, V., & Nikelsi, J. (1999).
Cerebral organization in bilinguals: A PET study of Chinese-English
verb generation. Neuroreport, 2841-2846.
Meuter, R. F. I., & Allport, A. ( 1999). Bilingual language switching in
naming: Asymmetrical costs of language selection. Journal of
memory and language, 25-40.
Rodriguez-Fornells, A., De Diego Balaguer, R., & Münte, T. F. (2006).
Executive control in bilingual language processing. Language
learning, 133-190.
Poster presentation in neurolinguistics 2007
Susanna Bernstrup