ON NOVEMBER 11, 1953, psychology professor B.F. Skinner sat in a fourth-grade math class, perturbed. It was Parents Day at his daughter Deborah’s school. The lesson 
seemed grossly inefficient: students proceeded through the material in lock-step, at the same pace; their graded assignments were returned to them sluggishly.
A leading proponent of what he called “radical behaviorism,” Skinner had devoted his career to studying feedback. He denied the existence of free will and dismissed inner mental states as explanations for outward action. Instead, he focused on the environment and the organism’s response. He had trained rats to push levers and pigeons to play Ping-Pong. A signed photo of Ivan Pavlov presided over his study in Cambridge. Turning his attention to a particular subset of the human animal—the schoolchild—Skinner invented his Teaching Machine.
