* The discovery of variable rewards happened by accident. One day in the lab, the famous Harvard psychologist B. F. Skinner was running low on food pellets during one experiment and making more was a time-consuming process because he had to manually press the pellets in a machine. This situation led him to “ask myself why every press of the lever had to be reinforced.” He decided to only give treats to the rats intermittently and, to his surprise, varying the delivery of food did not decrease behavior, but actually increased it.