The elimination of a conditioned response by withholding reinforcement.
In classical/respondent conditioning, the learned response disappears when the association between conditioned and unconditioned stimuli is eliminated. For example, when a conditioned stimulus (a light) is presented with an unconditioned stimulus (meat), a dog may be trained to salivate in response to the conditioned stimulus. If the unconditioned stimulus does not appear at least some of the time, however, its association with the conditioned stimulus will be lost, and extinction of the dog's learned or conditioned response will occur. As a result, the dog will stop salivating in response to the light.
In operant conditioning, the experimental subject acquires a conditioned response by learning that its actions will bring about specific consequences, either positive or negative. When the link between this operant response and its consequences is not reinforced, extinction of the response occurs. Thus, a rat that has learned that pressing a lever in its cage will produce a food pellet will gradually stop pressing the lever if the food pellets fail to appear.
Just as behavioral therapies use reinforcement to foster desirable behaviors, they may achieve the extinction of undesirable ones by removing various forms of reinforcement. For example, rowdy or otherwise inappropriate behavior by children is often "rewarded" by attention from both adults and peers. Sending a child to "time out" short circuits this process and can eliminate the undesirable behavior by removing the reward. Although it works slowly, extinction is a popular technique for modifying behavior in children.
Craighead, W. Edward. Behavior Modification: Principles, Issues, and Applications. Boston: Houghton Mifflin, 1976.
Skinner, B.F. About Behaviorism. New York: Knopf, 1974.