When her daughter Aeryn was about 3, Jean Player noticed a subtle change. Aeryn arrived home from daycare telling her mom not about the songs or the games but rather about the children she had played with. "She would talk about the kids, about how she wanted to see them, to call them on the phone," Player, of Somerville, Massachusetts, says. "It seemed like things were starting to broaden in her world."
As with many other children her age, Aeryn's social web was broadening. When they're born, babies are primed for social interaction -- think of those big eyes that just draw you in -- but with none of the skills required to engage with other people. Over the next three years, children go from caring about no one else but Mom to boiling with excitement about a playdate.