Nov 14, 2011
Dual language exposure in infancy can change neural and language processing in the developing brain: An fNIRS investigation
Kaja Jasinska (University of Toronto) and Laura-Ann Petitto (Gallaudet University)
Society for Neuroscience Control Number: 17724 Hot Topics Press Book 401.08/XX73 * = Petitto Corresponding Author
A new study, Jasinka and Petitto (2011), finds a remarkable language advantage in bilingual babies. They have a greater and longer sensitivity to language distinctions that make up the world’s languages, and show unique patterns of brain activation for language, as compared to monolingual babies. The findings, observed by a team led by Dr. Laura-Ann Petitto of Gallaudet University in Washington, D.C., reveal that early exposure to two languages changes the human brain in ways that afford linguistic advantages to young bilingual children.
As adults, we know well that it is hard to learn a new language like a pro later in life. Yet young monolingual babies begin life as “citizens of the world.” At birth, babies have the capacity to pick out the core language distinctions found in all human languages, specifically phonetic distinctions (the tiny parts of language structure). This capacity makes it possible for babies to learn any language in the world to which they may be exposed. Yet monolingual babies lose this universal capacity by around 14 months old. Not so for bilingual babies!
Petitto and graduate student Kaja Jasinska, used modern brain imaging technology, called functional Near Infrared Spectroscopy (fNIRS) to look inside of a bilingual baby’s brain. fNIRS measures changes in the brain’s blood flow in response to different types of linguistic and nonlinguistic stimuli. They wondered whether being bilingual, as compared to monolingual, would change a baby’s brain, and, consequently, whether this would have any linguistic advantages for the bilingual baby. A central puzzle for which the field had no answer regarding either group was whether young babies use the same classic language areas of the brain as adults, and whether the human brain changes based on bilingual versus monolingual language experience. Of particular interest here was the classic language area called the Superior Temporal Gyrus (STG, which is associated with processing phonetic chunks in language that comprise words, like “ba,” “pa”).
Thirty-two babies (four groups, eight babies per group, consisting of younger and older bilinguals, and younger and older monolinguals) listened to three types of stimuli in quasi random sequences (“Event” design): Native English (“ba,” “pa”), foreign language or Non-Native Hindi phonetic contrasts, and nonlinguistic Tones, while undergoing fNIRS.
When all children were listening to the linguistic units, they showed robust activity in the brain’s classic phonological processing tissue (STG), but not when listening to the nonlinguistic tones, answering an age-old question by showing that the babies’ language processing areas were similar to adults and working hard in early life!
Commensurate with the famous “loss” in phonetic discrimination, older monolingual babies showed decreased STG activity for language distinctions that they never heard before (the foreign/non-native phonetic units), even though their brains were very responsive to them when they were younger babies.
The greatest surprise was seen in the older bilingual babies. They showed robust neural sensitivity to the foreign language units, and this was not at the expense of sensitivity to their Native language contrasts, with its robust STG activation, suggesting a linguistic phonetic processing advantage in bilinguals.
Petitto noted “Bilingual brains provide a window into the full extent that our brain’s language processing tissue could potentially achieve.” Bilingual exposure may provide children with a linguistic “perceptual wedge” that holds open longer their capacity to process a fuller range of the world’s language structure. “What is clear is that early life Bilingual experience can change the brain in ways that provide powerful linguistic advantages to children, which has important implications for education.”