Extinction is a procedure whereby a posi tively or negatively reinforced response is decreased in strength or frequency by discontinuing the contingency of reinforcement maintaining it. During the acquisition phase, dogs learn that reinforcement or its omission depends on what they do. Under the extinction phase, they learn that the desired or expected consequence is no longer available for the same response. This does not imply that extinction is the functional opposite of learning, nor is it a passive effect based on response fatigue or some other such phenomenon (e.g., habituation), but rather extinction is the result of additional active learning about the relevant discriminative stimulus (Sd), response, and outcome (Sr+/_). Extinction results when the controlling Sd fails to predict the occurrence of the expected outcome for which the selected response is emitted, that is, to control the presentation of the positive reinforcer (Sr_) or to escape or avoid the occurrence of the negative reinforcer (Sr_). Consequently, during extinction, dogs learn not to respond in the presence of the signal since it no longer adequately predicts the occurrence or nonoccurrence of the anticipated attractive or aversive stimulus. However, extinguishing a response under the control of one Sd or signal does not mean that it will be adversely affected in the presence of other signals that still adequately predict reinforcement. In fact, if the previously disconfirmed signal again becomes predictive of reinforcement, the erstwhile extinguished response will quickly recover to its original strength.
Extinction procedures are often used to reduce attention-motivated disruptive behavior that is under the control of social contingencies of reinforcement (Ducharme and Van Houten, 1994). For example, many puppies rebel against being restrained in their crate at night, often exhibiting strong protestations in the form of barking and persistent efforts to escape. A concerned owner may reinforce this behavior by either attending to the puppy or, worse yet, by releasing the puppy from confinement. In cases where such a history of reinforcement is evident, extinction by simply ignoring the puppy often proves very effective. An interesting parallel case has been de scribed by Williams (1959), in which a dramatic reduction of "tyrant-like tantrum behavior" was expressed by a 2-year-old child whenever he was put to bed. The child quickly responded to the extinction efforts carried out by the family, until one night the child exhibited a period of tantrum behavior (spontaneous recovery) while an aunt was watching him. This single reinforcing event caused the tantrum behavior to recover, requiring that another series of extinction trials be carried out. After a few days, the behavior was fully suppressed.
As mentioned previously, the rate of extinction depends to a great extent on the reinforcement history controlling the targeted behavior. Behaviors maintained under an intermittent schedule of reinforcement tend to be more resistant to extinction than ones maintained under a CRF. Characteristically, intermittent reinforcement also tends to produce higher rates of responding than does reinforcement occurring on a continuous schedule. In some cases, therefore, especially involving difficult-to-extinguish behavior, it may make sense to place the unwanted behavior on a continuous schedule before proceeding to the extinction phase of training. At first, this sort of behavioral intervention may seem highly questionable (i.e., deliberately reinforcing unwanted behavior), but the evidence is fairly clear—such an approach tends to reduce the overall rate of responding while rendering the behavior more vulnerable to subsequent extinction efforts. Lerman and colleagues (1996) have successfully tested and confirmed the efficacy of a similar approach with human subjects exhibiting disruptive and aggressive behavior.
When an instrumental response undergoes extinction, it may actually intensify before beginning to decrease in strength. For example, if one wishes to extinguish begging behavior by withholding food treats, the frequency and magnitude of begging behavior may initially increase to levels exceeding pre-extinction operant levels. This so-called extinction burst or frustration effect is usually followed by a gradual decrease in response strength until the behavior is finally extinguished over the course of several non-reinforced trials.
After a day of rest following a series of extinction trials, a trainer may find that the behavior that he or she thought was extinguished the day before had meanwhile returned to nearly its full original strength. This phenomenon is referred to as spontaneous recovery, which frequently occurs after a rest period between extinction sessions. However, such recovered behavior is usually much more sensitive to subsequent extinction efforts, yielding more rapidly than before. Over the next several days, the begging behavior is apt to recover periodically but with progressively weaker strength and persistence. If the owner remains steadfast, the begging behavior will be eventually extinguished without further episodes of spontaneous recovery. If, however, the owner becomes lax or forgetful and gives the dog a single treat (intermittent reinforcement), future extinction efforts will be adversely impacted.
While extinction can be usefully employed to reduce the strength of an unwanted behavior, competing phenomena like bursts and spontaneous recovery make it an impractical training tool for many situations. Further, because extinction is essentially a punitive measure (the withdrawal of positive reinforcement is punishment), the dogs or puppies are not learning anything new—they are only learning that the behavior under extinction no longer produces the expected reinforcement. In the case of simple extinction, it is important to introduce and differentially reinforce an alternative or incompatible behavior to replace the one being extinguished.
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Getting a new puppy is a fun and interesting time. You probably went to a breeder or pet store or maybe just saw an ad on the Internet or the newspaper, for puppies, and decided just to check it out. Before you knew it those little eyes and fluffy puppy fur had your heart melting and you were headed home with him or her in your arms. If you are like most new pet owners you had visions of playing fetch with your dog, of watching him frolic at the lake, and of cuddling up on cold nights.