When we hold our babies for the first time, we might imagine that they're clean slates, unmarked by life, when in fact, they've already been shaped by us and by the particular world we live in. Today I want to share with you some of the amazing things that scientists are discovering about what fetuses learn while they're still in their mothers' bellies. First of all, they learn the sound of their mothers' voices. Because sounds from the outside world have to travel through the mother's abdominal tissue and through the amniotic fluid that surrounds the fetus, the voices fetuses hear, starting around the fourth month of gestation, are muted and muffled. One researcher says that they probably sound a lot like the the voice of Charlie Brown's teacher in the old "Peanuts" cartoon. But the pregnant woman's own voice reverberates through her body, reaching the fetus much more readily. And because the fetus is with her all the time, it hears her voice a lot. Once the baby's born, it recognizes her voice and it prefers listening to her voice over anyone else's.