What the bilingual brain tells us about language learning

By Arturo E. Hernandez

One of the most common questions people ask revolves around when and how to learn a second language. One common view is that earlier is better. There is good evidence for this view. A number of studies have found that the earlier a person learns a second language, the better they perform on a number of tests. Particularly sensitive to age is a person’s ability to speak without an accent and to detect speech sounds that are not present in their native language. For example, infants can detect sounds from a language not in their environment at six months of age. By 10 months of age they lose this ability. This suggests that the ability to detect speech sounds from around the globe is available to all infants but slowly fades away. Another arena where age plays a role is in the processing of grammar. Those who learn a second language later in life do not perform as well on tests of grammar as early learners. Hence, the ability to learn grammar and speech sounds appears to be very dependent on the age that one first learns a language.

Despite this general rule, there are some very interesting exceptions. For example, Christophe Pallier and his colleagues tested a group of adults who had been born in Korea and adopted as children in France between the ages of 4-8. This group of adults were asked to listen to sentences in Korean, French, or an unknown language. The results revealed no difference in their brain activity when compared to native French speakers. That is, both groups showed similar activity for French, Korean, and a foreign language. Furthermore, the Korean adoptees had no discernible accent. They sounded French. The results are intriguing because they suggest that a language can be lost even relatively late in childhood. This suggests that the age at which a language is learned is not the only predictor of how well a language is spoken as an adult.

This complex form of language representation is also found when observing the effects of brain damage on bilingual individuals. For over 100 years, neurologists and neuropsychologists had observed a lot of differences in the pattern of language loss in bilinguals. There were cases of people who lost access to one or both languages after suffering brain damage. Some lost access to the first language and others lost access to the second language. I also experienced a brief period of language inaccessibility when immersed in Portuguese, my third language. When I returned from my time abroad, I began to read about cases of bilingual aphasia. The resonance between language loss due to stroke and what I had experienced was interesting. I wondered why there was such a dynamic aspect to language access in bilinguals — questions that I began to ask myself 24 years ago.

Arturo Hernandez is currently Professor of Psychology and Director of the Developmental Cognitive Neuroscience graduate program at the University of Houston. He is the author of The Bilingual Brain. His major research interest is in the neural underpinnings of bilingual language processing and second language acquisition in children and adults. He has used a variety of neuroimaging methods as well as behavioral techniques to investigate these phenomena which have been published in a number of peer reviewed journal articles. His research is currently funded by a grant from the National Institutes of Child Health and Human Development.

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Image credit: Thinker, created by Auguste Rodin at the end of the 18 century. San Francisco Legion of Honor. © rramirez125 via iStockphoto.

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