It's almost instinctive -- you see an adorable baby, and you start to coo, smile or make a face to elicit some kind of response. But even if you get a blank stare back, rest assured that the tyke is processing every change in the shape and rhythm of your mouth and face. Researchers, led by Whitney Weikum at the University of British Columbia, found that infants under 8 months old may rely on such visual cues to learn language, even using variations in facial expressions to distinguish one language from another.
Working with babies raised in two different language environments--one in which English was the only language spoken and another in which the parents used both English and French--the team of scientists played silent video clips of English- and French-speaking adults reading in each language. Babies at 4 and 6 months old noticed the difference in facial expressions when the language was switched, and paid more attention to the clips after such a swap than when all the readings were in the same language. By 8 months, however, only infants reared in bilingual homes retained the ability to make this distinction.
Which makes perfect sense. At birth, babies need to be receptive to any language and the facial cues that differentiate them. With time, they learn to focus on the sounds, muscle movements and facial rhythms of only the languages to which they are exposed. It's all part of the way babies learn, by processing stimuli from a range of senses; even language, it seems, depends on visual triggers. So go ahead and coo at the next infant you encounter. Just be expressive about it.