How Will A.I. Learn Next?

The Web site Stack Overflow was created in 2008 as a place for programmers to answer one another's questions. At the time, the Web was thin on high-quality technical information; if you got stuck while coding and needed a hand, your best bet was old, scattered forum threads that often led nowhere. Jeff Atwood and Joel Spolsky, a pair of prominent software developers, sought to solve this problem by turning programming Q. & A. into a kind of multiplayer game. On Stack Overflow--the name refers to a common way that programs crash--people could earn points for posting popular questions and leaving helpful answers. Points earned badges and special privileges; users would be motivated by a mix of altruism and glory.