May 24, 2007 -- Just by reading grown-ups' faces, babies may notice when bilingual adults shift from one language to another, a new study shows.
The study, published in the journal Science, included 96 healthy, full-term babies aged 4 months, 6 months, and 8 months.
Some of the babies were from families that only spoke English. The other babies were from bilingual families that spoke English and French.
One by one, the babies sat on their parent's lap and watched a silent video tape play on a TV screen.
The video showed an adult reciting French and English sentences from a classic book by Antoine de Saint-Exupery published in English as The Little Prince and as Le Petit Prince in French.
The researchers included neuroscience doctoral student Whitney Weikum of Canada's University of British Columbia. They filmed the babies during the experiment to see how long the babies watched the silent videos.
Across the board, babies aged 4 months and 6 months watched the videos longer when the speakers switched languages, even though the speakers' words couldn't be heard.
The babies may have noticed how the grown-ups' faces changed in speaking different words, note the researchers.
Among the 8-month-old babies, only those raised in bilingual homes kept paying more attention to the language shifts. Those babies' bilingual upbringing may have reinforced their interest in telling the two languages apart, the researchers suggest.
Weikum tells WebMD that she and her colleagues are interested to see if the findings hold for languages that have more rhythmic similarities than English and French.