 Haidt cited research indicating that this sort of play is necessary to wire up the brains of all mammals, including us humans, and Haidt called this the decline of play-based childhoods. That was villain number one. Then there was a second villain, the one Haidt had zeroed in on as the bad guy of his book, the smartphone. The smartphone was introduced to the public in 2007 by Steve Jobs and imitated by South Korea's Samsung in 2009.