the use of the bow and arrow knew that the son needed plenty of practice and that he had to see where the arrow went on each shot if he was to make any improvement on the next. The importance of this immediate feedback was formulated years ago by Thorndike as the “law of effect.” According to this law of learning, an action which leads to a satisfactory result tends to be repeated. In the contemporary terminology of B.F. Skinner, of Harvard University, immediate reinforcement or reward is important in the learning process. As far as the application of this principle is concerned, we do a much better job of teaching rats, pigeons, and football players than we do in teaching mathematicians and physicists. Teaching machines designed for individual use make it possible to provide this immediate reinforcement for every student…. Laboratory experiments have demonstrated that the use of immediate reinforcement techniques is a very efficient way of training animals to make a discriminative response to selected stimuli. Rats and pigeons can be trained to perform a whole series of such responses in sequence. Their actions then form a complicated “chain” of events.... The only reason a rat should turn to the right rather than the left at a certain point is that it is that turn which leads to reinforcement. (p. 402)