n 1930, a psychologist at Harvard University called B.F. Skinner made a box and placed a hungry rat inside it. The box had a lever on one side. As the rat moved about it would accidentally knock the lever and, when it did so, a food pellet would drop into the box. After a rat had been put in the box a few times, it learned to go straight to the lever and press it: the reward reinforced the behaviour. Skinner proposed that the same principle applied to any “operant”, rat or man. He called his device the “operant conditioning chamber”. It became known as the Skinner box.