Wow! Apparently babies study facial movements associated with speaking, and for their first six months, pay closer attention when the face on a soundless video is speaking a different language. By eight months of age, babies in monolingual families lose the ability to tell the difference. You can read more about Whitney Weikum and Janet Werker’s (with others) research on this topic at ScienceNews.org. While you’re there you might like to check out the Science News for Kids page.