Learning

C

Applications of Classical Conditioning

After studying classical conditioning in dogs and other animals, psychologists became interested in how this type of learning might apply to human behavior. In an infamous 1921 experiment, American psychologist John B. Watson and his research assistant Rosalie Rayner conditioned a baby named Albert to fear a small white rat by pairing the sight of the rat with a loud noise. Although their experiment was ethically questionable, it showed for the first time that humans can learn to fear seemingly unimportant stimuli when the stimuli are associated with unpleasant experiences. The experiment also suggested that classical conditioning accounts for some cases of phobias, which are irrational or excessive fears of specific objects or situations. Psychologists now know that classical conditioning explains many emotional responses—such as happiness, excitement, anger, and anxiety—that people have to specific stimuli. For example, a child who experiences excitement on a roller coaster may learn to feel excited just at the sight of a roller coaster. For an adult who finds a letter from a close friend in the mailbox, the mere sight of the return address on the envelope may elicit feelings of joy and warmth.

Psychologists use classical conditioning procedures to treat phobias and other unwanted behaviors, such as alcoholism and addictions. To treat phobias of specific objects, the therapist gradually and repeatedly presents the feared object to the patient while the patient relaxes. Through extinction, the patient loses his or her fear of the object. In one treatment for alcoholism, patients drink an alcoholic beverage and then ingest a drug that produces nausea. Eventually they feel nauseous at the sight or smell of alcohol and stop drinking it. The effectiveness of these therapies varies depending on the individual and on the problem behavior. See Psychotherapy: Behavioral Therapies.

D

Contemporary Theories

Modern theories of classical conditioning depart from Pavlov’s theory in several ways. Whereas Pavlov’s theory stated that the conditioned and unconditioned stimuli should elicit the same type of response, modern theories acknowledge that the conditioned and unconditioned responses frequently differ. In some cases, especially when the unconditioned stimulus is a drug, the conditioned stimulus elicits the opposite response. Modern research has also shown that conditioning does not always require a close pairing of the two stimuli. In taste-aversion learning, people can develop disgust for a specific food if they become sick after eating it, even if the illness begins several hours after eating.

Psychologists today also recognize that classical conditioning does not automatically occur whenever two stimuli are repeatedly paired. For instance, suppose that an experimenter conditions a dog to salivate to a light by repeatedly pairing the light with food. Next, the experimenter repeatedly pairs both the light and a tone with food. When the experimenter presents the tone by itself, the dog will show little or no conditioned response (salivation), because the tone provides no new information. The light already allows the dog to predict that food will be coming. This phenomenon, discovered by American psychologist Leon Kamin in 1968, is called blocking because prior conditioning blocks new conditioning.

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IV

Operant Conditioning

One of the most widespread and important types of learning is operant conditioning, which involves increasing a behavior by following it with a reward, or decreasing a behavior by following it with punishment. For example, if a mother starts giving a boy his favorite snack every day that he cleans up his room, before long the boy may spend some time each day cleaning his room in anticipation of the snack. In this example, the boy’s room-cleaning behavior increases because it is followed by a reward or reinforcer.

Unlike classical conditioning, in which the conditioned and unconditioned stimuli are presented regardless of what the learner does, operant conditioning requires action on the part of the learner. The boy in the above example will not get his snack unless he first cleans up his room. The term operant conditioning refers to the fact that the learner must operate, or perform a certain behavior, before receiving a reward or punishment.

A

Thorndike’s Law of Effect

Some of the earliest scientific research on operant conditioning was conducted by American psychologist Edward L. Thorndike at the end of the 19th century. Thorndike’s research subjects included cats, dogs, and chickens. To see how animals learn new behaviors, Thorndike used a small chamber that he called a puzzle box. He would place an animal in the puzzle box, and if it performed the correct response (such as pulling a rope, pressing a lever, or stepping on a platform), the door would swing open and the animal would be rewarded with some food located just outside the cage. The first time an animal entered the puzzle box, it usually took a long time to make the response required to open the door. Eventually, however, it would make the appropriate response by accident and receive its reward: escape and food. As Thorndike placed the same animal in the puzzle box again and again, it would make the correct response more and more quickly. Soon it would take the animal just a few seconds to earn its reward.

Based on these experiments, Thorndike developed a principle he called the law of effect. This law states that behaviors that are followed by pleasant consequences will be strengthened, and will be more likely to occur in the future. Conversely, behaviors that are followed by unpleasant consequences will be weakened, and will be less likely to be repeated in the future. Thorndike’s law of effect is another way of describing what modern psychologists now call operant conditioning.

B

B. F. Skinner’s Research

American psychologist B. F. Skinner became one of the most famous psychologists in history for his pioneering research on operant conditioning. In fact, he coined the term operant conditioning. Beginning in the 1930s, Skinner spent several decades studying the behavior of animals—usually rats or pigeons—in chambers that became known as Skinner boxes. Like Thorndike’s puzzle box, the Skinner box was a barren chamber in which an animal could earn food by making simple responses, such as pressing a lever or a circular response key. A device attached to the box recorded the animal’s responses. The Skinner box differed from the puzzle box in three main ways: (1) upon making the desired response, the animal received food but did not escape from the chamber; (2) the box delivered only a small amount of food for each response, so that many reinforcers could be delivered in a single test session; and (3) the operant response required very little effort, so an animal could make hundreds or thousands of responses per hour. Because of these changes, Skinner could collect much more data, and he could observe how changing the pattern of food delivery affected the speed and pattern of an animal’s behavior.

Skinner became famous not just for his research with animals, but also for his controversial claim that the principles of learning he discovered using the Skinner box also applied to the behavior of people in everyday life. Skinner acknowledged that many factors influence human behavior, including heredity, basic types of learning such as classical conditioning, and complex learned behaviors such as language. However, he maintained that rewards and punishments control the great majority of human behaviors, and that the principles of operant conditioning can explain these behaviors.

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