1187068851chapter9-sec4

Chapter 9 - Motivational Strategies ____________________________________________________

Extinction ___________________________________________

What do you think would happen if a dog who had become classically conditioned to salivate at the ringing of a bell never again received food when the bell was rung? The answer lies in one of the basic phenomena of learning: extinction.

Extinction occurs when a previously conditioned response decreases in frequency and eventually disappears.

To produce extinction, one needs to end the association between conditioned and unconditioned stimuli. For instance, if we had trained a dog to salivate at the ringing of a bell, we could produce extinction by ceasing to provide meat after the bell was rung. At first, the dog would continue to salivate when it heard the bell, but after a few such instances, the amount of salivation would probably decline and the dog would eventually stop responding to the bell altogether. At that point, we could say that the response had been extinguished. In summary, extinction occurs when the conditioned stimulus is repeatedly presented without the unconditioned stimulus. We should keep in mind that extinction can be a helpful phenomenon. Consider, for instance, what it would be like if the fear you experienced while watching The Exorcist never was extinguished. You might well tremble with fright every time you entered your bedroom.

Psychologists have treated people with irrational fears, or phobias, by using a form of therapy called systematic desensitization. The goal of systematic desensitization is to bring about the extinction of the phobia. For example, a therapist using systematic desensitization for a client who is afraid of dogs might repeatedly expose the client to dogs, starting with a less frightening aspect (a photo of a cute dog) and moving toward more feared ones (such as an actual encounter with an unfamiliar dog). As the anticipated negative consequences of exposure to the dog (e.g., being jumped on or bitten) do not occur, the fear eventually becomes extinguished.

Once a conditioned response has been extinguished, has it vanished forever? Not necessarily. Pavlov discovered this when he returned to his dog a few days after the conditioned behavior had seemingly been extinguished.

If he rang a bell, the dog once again salivated…an effect known as spontaneous recovery, or the reemergence of an extinguished conditioned response after a period of rest.

Spontaneous recovery helps explain why it is so hard to overcome drug addictions. For example, cocaine addicts who are thought to be “cured” could experience an irresistible impulse to use the drug again if they are subsequently confronted by a stimulus with strong connections to the drug, such as a white powder. If you are saying to yourself, “I heard this before,” you are perfectly right. I discussed this procedure in chapter 7 when I was talking about The Exorcist. Remember, I used the same exact method to desensitize the fear the students had to the movie.

Generalization and Discrimination _________________________________________________________________________________________

Despite differences in color and shape, to most of us, a rose is a rose. The pleasure we experience at the beauty, smell, and grace of the flower is similar for different types of roses. Pavlov noticed a similar phenomenon. His dogs often salivated not only at the ringing of the bell that was used during their original conditioning, but at the sound of a buzzer as well.

Such behavior is the result of stimulus generalization. Stimulus generalization takes place when a conditioned response follows a stimulus that is similar to the original conditioned stimulus. The greater the similarity between the two stimuli, the greater the likelihood of stimulus generalization. Baby Albert, who was conditioned to be fearful of rats, was later found to be afraid of other furry white things as well. He was fearful of white rabbits, white fur coats, and even a white Santa Clause mask. On the other hand, according to the principle of stimulus generalization, it is unlikely that he would have been afraid of a black dog because its color would differentiate it sufficiently from the original fear-evoking stimulus. The conditioned response elicited by the new stimulus is usually not as intense as the original conditioned response, although the more similar the new stimulus is to the old one, the more similar the new response will be. It is unlikely, then, that Albert's fear of the Santa Clause mask was as great as his learned fear of a rat. Still, stimulus generalization permits us to know, for example, that we ought to brake at all red lights, even if there are minor variations in size, shape, and

Chapter 9 - Motivational Strategies ____________________________________________________

shade.

If two stimuli are sufficiently distinct from one another so that one evokes a conditioned response but the other does not, we can say that stimulus discrimination has occurred. Stimulus discrimination is the ability to differentiate between stimuli. For example, the ability to discriminate between a red and a green traffic light prevents us from getting mowed down by oncoming traffic at intersections.

Beyond Traditional Classical Conditioning: Challenging Basic Assumptions _______________________________________________________________________________________________________________________________________________________________________

Although Pavlov hypothesized that all learning is nothing more than long strings of conditioned responses, this notion has not been supported by subsequent research. It turns out that classical conditioning provides us with only a partial explanation of how people and animals learn and that Pavlov was wrong in some of his basic assumptions.

For example, according to Pavlov, the process of linking stimuli and responses occurs in a mechanistic, unthinking way. In contrast to this perspective, learning theorists influenced by cognitive psychology have argued that learners actively develop an understanding and expectancy about which particular unconditioned stimuli are matched with specific conditioned stimuli.

A ringing bell, for instance, gives a dog something to think about: the impending arrival of food.

Traditional explanations of how classical conditioning operates have also been challenged by learning psychologist John Garcia, whose research was initially concerned with the effects of exposure to nuclear radiation on laboratory animals. In the course of his experiments, he realized that rats placed in a radiation chamber drank almost no water, even though in their home cage they drank eagerly. The most obvious explanation…that it had something to do with the radiation…was soon ruled out.

Garcia found that even when the radiation was not turned on, the rats still drank little or no water in the radiation chamber.

Initially puzzled by the rats‟ behavior, Garcia eventually figured out that the drinking cups in the radiation chamber were made of plastic, thereby giving the water an unusual, plastic-like taste. In contrast, drinking cups in the home cage were made of glass and left no abnormal taste.

As a result, the plastic-tasting water had become repeatedly paired with illness brought on by exposure to radiation, and that had led the rats to form a classically conditioned association. The process began with the radiation acting as an unconditioned stimulus evoking the unconditioned response of sickness. With repeated pairings, the plastic-tasting water had become a conditioned stimulus that evoked the conditioned response of sickness.

This finding violated one of the basic rules of classical conditioning…that an unconditioned stimulus should immediately follow a conditioned stimulus for optimal conditioning to occur.

Instead, Garcia‟s findings showed that conditioning could occur even when there was an interval of as long as eight hours between exposure to the conditioned stimulus and the response of sickness.

Furthermore, the conditioning persisted over very long periods and sometimes occurred after just one exposure to water that was followed later on by illness.

These findings have had important practical implications. For example, to prevent coyotes from killing their sheep, some ranchers now routinely lace a sheep carcass with a drug and leave the carcass in a place where coyotes will find it.

The drug temporarily makes the coyotes quite ill, but it does not permanently harm them. After just one exposure to a drug-laden sheep carcass, coyotes avoid sheep, which are normally one of their primary natural victims.