It’s a good thing that the movie Inglourious Basterds has subtitles, because everyone except the Americans are always switching languages. Now imagine that you see a silent clip from the movie — do you think you’d be able to tell when someone starts speaking a different language? If you’ve ever tried figuring out what someone is saying just from looking at their mouth, you’ll know it’s not easy. What if you showed Inglourious Bastards to a baby — would it be able to detect a language switch if the sound were turned off? Since babies often seem more like blobs than humans, you might think not. Amazingly, we’ve recently discovered that 8 month-old infants CAN tell the difference — but only if they’re bilingual.
How can babies, who can’t even understand what their parents are saying, tell when a silent face switches languages? And how can you test a baby to figure this out? Whitney Weikum and her colleagues had babies sit on a parent’s lap and watch silent videos clips of 3 different women reading children’s stories. Babies saw lots of similar video clips all in the same language (English) until they stopped looking at them as much. Just like when you look away from something when you’re bored with it, so will babies.
Suddenly, the language in the videos switched: although the same 3 women were reading stories in silent videos, now they were reading them in a different language. Now French-English bilingual babies returned to looking at the videos. They noticed that the language changed, and became interested in the videos again. Since the videos were silent, the only clues they could have used were the way the women’s faces and mouths moved. So babies who can’t even talk were using these very subtle differences to tell languages apart.
Not all babies were equally good at this test, though: monolingual English-speaking 8 month-olds couldn’t tell the difference when the languages switched. But when monolingual babies were younger (4-6 months old), they could. Why is this? It seems like all babies start out with the ability to tell languages apart just from looking at people’s faces when they’re speaking. But since this skill is only really helpful for babies exposed to more than one language on a regular basis, bilingual babies use it and monolinguals loose it.
Rather than being confused by constantly switching languages at home, bilingual babies are actually quite good at telling them apart — even just from tiny differences in people’s facial expressions. When it comes to language learning, babies are very intelligent blobs.
Weikum, W., Vouloumanos, A., Navarra, J., Soto-Faraco, S., Sebastian-Galles, N., & Werker, J. (2007). Visual Language Discrimination in Infancy Science, 316 (5828), 1159-1159 DOI: 10.1126/science.1137686