Although the term reinforcement has many common uses and associated meanings, its meaning is precise when used by behavior analysts and behavior therapists. The act or process of making a reinforcer contingent on behavior is termed positive reinforcement, and a reinforcer is any object or event that, when delivered following some behavior, increases the probability that the behavior will occur again. A typical example might evolve from a laboratory experiment with rats. A rat is placed in a small plastic chamber. The rat can press a lever located on one wall of the chamber. When the rat presses the lever, a small food pellet drops into a dish. If the rat returns to the lever and continues to press it would be said that the food pellet functions as a reinforcer that the behavior is maintained by positive reinforcement.

There is often confusion between positive reinforcement and negative...