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Behaviors maintained by consistent and predictable reinforcement are highly sensitive to discontinuing reinforcement (Williams 1994). For example, if someone pressed an elevator button, but it didn’t light up to indicate that an elevator was on its way, what would the person do? Most people would press the button again, maybe a few more times in rapid succession, or hold the button down harder and longer than usual. After a few attempts, most people would eventually just take the stairs. The process by which a response stops occurring when reinforcement no longer follows the behavior is termed extinction.

Extinction can be both a process and a procedure. Extinction as a procedure entails withholding the reinforcer that previously maintained a response. Extinction as a process involves the decrease and eventual elimination of a response. It is important to note this difference because for extinction as a process to successfully occur, the reinforcer that is maintaining the response must be identified. Sometimes we assume that a behavior is maintained by a certain reinforcer, but relying on assumptions can lead us astray when trying to implement extinction to decrease behavior.

The discovery of extinction as a behavioral process in operant conditioning was completely serendipitous (Skinner 1956). Skinner was running an experiment in which a rat pressed a lever for food. Unbeknownst to Skinner, the pellet dispenser jammed at some point during the session. Therefore, presses on the lever no longer produced reinforcement and underwent extinction. The rat didn’t immediately stop pressing the lever; instead, there was a gradual reduction in the number of lever presses before the behavior finally stopped. Skinner’s accidental demonstration of extinction highlights an important feature of the process: the behavior under extinction diminishes gradually, not in an all‐or‐none fashion. How quickly behavior decreases during extinction is a function of the schedule of reinforcement that maintained the behavior, the length of time the behavior has been in the animal’s repertoire, and whether conditioned reinforcers are delivered during extinction.

At the beginning of the extinction process, an increase in frequency or intensity of the behavior, called an extinction burst, may occur. Extinction bursts can make the use of extinction difficult when the intention is to reduce behavior. Many pet owners are familiar with a dog who persistently begs during dinner time. She might sit politely by the dining table waiting for the usual handout. The dog has a long history of reinforcement for begging at the table and has learned some methods that might increase the odds of her getting a snack. When she is ignored, she might escalate to whining. When that doesn’t work, she might start to bark. The barking can be pretty annoying, making it really difficult to continue ignoring her. If the owner gives the dog food at that point, he or she would have been relieved of the dog’s barking temporarily but would have also reinforced barking as a way to get food. In addition, it teaches the dog to be further resistant to extinction because the owner has effectively thinned the reinforcement schedule. Using an extinction procedure can take a long time, and owners must wait for the extinction burst to subside before the begging behavior is completely extinguished. When begging no longer occurs, the association between begging at the dinner table and getting food is overridden by the new learning that begging does not result in food.

Extinction and reinforcement are used in combination to teach new behaviors through a technique called shaping. In shaping, a behavior is trained by reinforcing responses with forms that are closer and closer to a final desired behavior. In the laboratory, a common scenario is for a rat to press a lever for food. However, when a rat is put in the operant chamber for the very first time, it is highly unlikely that he would press the lever since the lever‐press response and the reinforcer have yet to be associated. Experimenters must first shape the lever‐press response before they can run their experiments. As the rat sniffs around the operant chamber and looks in the direction of the lever, the experimenter delivers a food pellet. As the rat moves progressively closer, each approach is reinforced with a food pellet. The experimenter might then wait for the rat to place his paw on the lever before delivering food. And finally, the rat presses down on the lever, exhibiting the final desired behavior. As successive approximations to a lever press are reinforced, previous responses that had formerly been reinforced are extinguished.