It shows up before the first word, lasts a lifetime, and scientists are still rethinking what it means.
Doctors watching for early signs of autism pay close attention to how a baby plays which classic hide-your-face game?
Peek-a-boo
Trouble with back-and-forth games like peek-a-boo and pat-a-cake, along with little babbling, is one of the most common early signs of autism.