“Watson,” an IBM computing system, is gearing up for a first-of-its-kind challenge—taking on human contestants on the game show Jeopardy! With a brain the size of 2,400 home computers and a database of about 10 million documents, will Watson be able to compute its way to victory? Win or lose, the difficulty of mimicking the human thought process with software is showing artificial-intelligence researchers that there’s more than one way to be “intelligent.”