Post written by François Grosjean.
As I mentioned in a previous post, I have defended over the years a view which proposes that bilinguals are not the sum of two complete or incomplete monolinguals (see here). The coexistence and constant interaction of the two or more languages in bilinguals has produced specific processing characteristics that cohabit with general characteristics common to all users of language.
In the domain of speech perception and comprehension, for example, bilinguals go through the same major stages as monolinguals when processing an utterance: they identify the speech sounds and recognize the words that are uttered, they do syntacting and semantic processing, and they undertake pragmatic processing which takes into account the context in which the utterance is said, the listener's knowledge of the world, and the rules of communication in order to produce a final enriched meaning of the utterance.
However, because bilinguals speak two or more languages, they differ from monolinguals in a number of ways when they process language. We know, for example, that the perception system of bilinguals is dynamic and will operate in different activation states–monolingual or bilingual–depending on a number of linguistic, psycholinguistic and sociolinguistic factors (see here). We know also that certain mechanisms in the bilinguals' second language will never be acquired, or only partly acquired, in particular when they started learning it late (see here).
With the increased use of brain imaging, along with more traditional behavioral experimentation, great strides are being made in our understanding of how bilinguals process language. One recent study, which has been talked about extensively in the media, was conducted by Professor Viorica Marian along with colleagues from Northwestern University and the University of Houston. They wanted to study phonological competition during spoken language processing in both monolinguals and bilinguals and they obtained both behavioral data–accuracy and response time–and brain imaging data.
English monolinguals and Spanish-English bilinguals were placed individually in a scanner and were asked to search for a picture of an object (the target) that corresponded to a word presented to them in English. They saw an array of four pictures and they used a button box to indicate the position of the target picture. At various points during the experiment, the word representing one of the other objects had the same beginning as the word representing the target. So, for example, if the target object represented a candy, the other object represented a candle. The presence of this other object created a momentary competition which ended when "candy" was fully heard and the participants pressed on the "candy" button. This type of phonological competition is common in spoken word recognition, even when we are not looking at something, since many other words in our minds have the same beginning as the one being uttered and we have to deactivate them (some say, inhibit them) as we are listening.
The results obtained showed that both monolinguals and bilinguals were very accurate in their responses, but they did respond more slowly when the competitor picture was present than when it was absent, as was expected. There were no differences between monolinguals and bilinguals at this level. However, when the imaging results were compared, the researchers found that bilinguals displayed substantially less cortical activation compared to monolinguals who showed greater activation in frontal regions (executive control areas) as well as the primary visual cortex. The conclusion the study arrived at makes sense: both monolinguals and bilinguals experienced competition, as indexed by slower response times in competition conditions, whereas the two groups recruited different neural resources to manage this competition.
The interpretation the authors had of these results will be debated for some time though. They proposed that bilinguals may be more efficient at managing phonological competition. General media accounts amplified this interpretation and took it out of context to produce titles such as, "Study shows that people who speak two languages have more efficient brains" (Washington Post), "Bilingual people are like brain 'bodybuilders'" (Discovery News) and "Bilingual brains may be better at processing language and cognitive information" (The Hearing Review).
I wrote to Viorica Marian to ask her a few questions and two of her answers reassured me. First, she clearly stated that monolinguals and bilinguals are both competent language processors and are able to process language in real time. She also stated that monolinguals are just as efficient as they need to be to process the types of linguistic demands that they typically face. As concerns bilinguals, Viorica Marian thinks that their experiences involve between-language competition in addition to within-language competition and that this may change the way they process language.
In the long run, both monolinguals and bilinguals have to do extensive processing of language (think of the number of hours a day we listen to people speaking), and have to do it efficiently. They'll do it in similar ways at some levels and differently at others–and this is what bilingualism processing research will continue to examine in the years to come.
Photo of speaking girlfriends at a cafe table from Shutterstock.
Viorica Marian, Sarah Chabal, James Bartolotti, Kailyn Bradley, and Arturo E. Hernandez (2014). Differential recruitment of executive control regions during phonological competition in monolinguals and bilinguals. Brain and Language, 139, 108-117.
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François Grosjean's website.