We found that bilingual children were better than monolingual children at this task. If you think about it, this makes intuitive sense. Interpreting someone’s utterance often requires attending not just to its content, but also to the surrounding context. What does a speaker know or not know? What did she intend to convey? Children in multilingual environments have social experiences that provide routine practice in considering the perspectives of others: They have to think about who speaks which language to whom, who understands which content, and the times and places in which different languages are spoken.

Interestingly, we also found that children who were effectively monolingual yet regularly exposed to another language — for example, those who had grandparents who spoke another language — were just as talented as the bilingual children at this task. It seems that being raised in an environment in which multiple languages are spoken, rather than being bilingual per se, is the driving factor.

You might wonder whether our findings could be explained as just another instance of the greater cognitive skills that bilingual children have been observed to have. We wondered that, too. So we gave all the children a standard cognitive test of executive function. We found that bilingual children performed better than monolingual children, but that the kids who were effectively monolingual yet regularly exposed to another language did not. These “exposure” children performed like monolinguals on the cognitive task, but like bilinguals on the communication task. Something other than cognitive skills — something more “social” — must explain their facility in adopting another’s perspective.

In a follow-up study, forthcoming in the journal Developmental Science, my colleagues and I examined the effects of multilingual exposure on even younger children: 14- to 16-month-old babies, who are hardly speaking at all. In this study, led by Zoe Liberman and in collaboration with Professor Keysar and the psychologist Amanda Woodward, babies were shown two versions of the same object, such as a banana, one of which was visible to both the infant and an adult, the other visible to the baby yet hidden from the adult’s view. When the adult asked the baby for “the banana,” the baby might hand her either object — both were bananas, after all — yet if the baby understood the social context, he would reach more often for the banana that the adult could see.