 He said that parents, starting in the 1980s, no longer allowed their kids to go off with their friends and play without adult supervision. Haight cited research indicating that this sort of play is necessary to wire up the brains of all mammals, including us humans, and Haight called this the decline of play-based childhoods. That was villain number one. Then there was a second villain, the one Haight had zeroed in on as the bad guy of his book, the smartphone.