5 Steps to a 5 AP Psychology, 2010-2011 Edition (32 page)

Social learning

Biological factors in learning

Preparedness evolves

Instinctive draft

In
classical conditioning
, the subject learns to give a response it already knows to a new stimulus. The subject associates a new stimulus with a stimulus that automatically and involuntarily brings about the response. A
stimulus
is a change in the environment that elicits (brings about) a response. A
response
is a reaction to a stimulus. When food—a stimulus—is placed in our mouths, we automatically salivate—a response. Because we do not need to learn to salivate to food, the food is an unconditional or unconditioned stimulus, and the salivation is an unconditional or unconditioned response. In the early 1900s, Russian physiologist Ivan Pavlov scientifically studied the process by which associations are established, modified, and broken. Pavlov noticed that dogs began to salivate as soon as they saw food (i.e., even before the food was placed in their mouths). The dogs were forming associations between food and events that preceded eating the food. This simple type of learning is called Pavlovian or classical conditioning.

In classical conditioning experiments, two stimuli, the unconditioned stimulus and neutral stimulus, are paired together. A
neutral stimulus (NS)
initially does not elicit a response. The
unconditioned stimulus (UCS
or
US)
reflexively, or automatically, brings about the
unconditioned response (UCR
or
UR)
. The
conditioned stimulus (CS)
is a
neutral stimulus (NS)
at first, but when paired with the UCS, it elicits the conditioned response (CR). During Pavlov’s training trials, a bell was rung right before the meat was given to the dogs. By repeatedly pairing the food and the bell,
acquisition
of the conditioned response occurred; the bell alone came to elicit salivation in the dogs. This exemplified the classical conditioning paradigm or pattern—

If you are having trouble figuring out the difference between the UCS and the CS, ask yourself these questions: What did the organism LEARN to respond to? This is the CS. What did the organism respond to REFLEXIVELY? This is the US. The UCR and the CR are usually the same response.

In classical conditioning, the learner is passive. The behaviors learned by association are elicited from the learner. The presentation of the US strengthens or reinforces the behavior. A learning curve for classical conditioning is shown in
Figure 10.1
.

Does the timing of presentation of the NS and US matter in establishing the association for classical conditioning? Different experimental procedures have tried to determine the best presentation time for the NS and the UCS, so that the NS becomes the CS.
Delayed conditioning
occurs when the NS is presented just before the UCS, with a brief overlap between the two.
Trace conditioning
occurs when the NS is presented and then disappears before the UCS appears.
Simultaneous conditioning
occurs when the UCS and NS are paired together at the same time. In
backward conditioning
, the UCS comes before the NS. In general, delayed conditioning produces the strongest conditioning, trace conditioning produces moderately strong conditioning, simultaneous conditioning produces weak conditioning, and backward conditioning produces no conditioning except in unusual cases. A pregnant woman who vomits hours after eating a burrito often will not eat a burrito again, which is a case of rare backward conditioning.

Figure 10.1 Classical conditioning learning curve
.

The strength of the UCS and the saliency of the CS in determining how long acquisition takes have also been researched. In the 1920s, John B. Watson and Rosalie Rayner conditioned a nine-month-old infant known as Baby Albert to fear a rat. Their research would probably be considered unethical today. The UCS in their experiment was a loud noise made by hitting a steel rod with a hammer. Immediately Albert began to cry, a UCR. Two months later, the infant was given a harmless rat to play with. As soon as Albert went to reach for the rat (NS), the loud noise (UCS) was sounded again. Baby Albert began to cry (UCR). A week later, the rat (CS) was reintroduced to Albert and without any additional pairings with the loud noise, Albert cried (CR) and tried to crawl away. Graphs of the learning curve in most classical conditioning experiments show a steady upward trend over many trials until the CS–UCS connection occurs. In most experiments, several trials must be conducted before acquisition occurs, but when an unconditioned stimulus is strong and the neutral stimulus is striking or salient, classical conditioning can occur in a single trial. Because the loud noise (UCS) was so strong and the white rat (CS) was salient, which means very noticeable, the connection between the two took only one trial of pairing for Albert to acquire the new CR of fear to the rat (CS). This experiment is also important because it shows how phobias and other human emotions might develop in humans through classical conditioning. Conditioning involving an unpleasant or harmful unconditioned stimulus or reinforcer, such as this conditioning of Baby Albert, is called
aversive conditioning
.

Unfortunately, Watson and Rayner did not get a chance to rid Baby Albert of his phobia to the rat. In classical conditioning, if the CS is repeatedly presented without the UCS, eventually the CS loses its ability to elicit the CR. Removal of the UCS breaks the connection and extinction, weakening of the conditioned association, occurs. If Watson had continued to present the rat (CS) and taken away the fear-inducing noise (UCS), eventually Baby Albert would probably have lost his fear of the rat. Although not fully understood by behaviorists, sometimes the extinguished response will show up again later without the repairing
of the UCS and CS. This phenomenon is called
spontaneous recovery
. If Baby Albert had stopped crying whenever the rat appeared, but 2 months later saw another rat and began to cry, he would have been displaying spontaneous recovery. Sometimes a CR needs to be extinguished several times before the association is completely broken.

Generalization
occurs when stimuli similar to the CS also elicit the CR without any training. For example, when Baby Albert saw a furry white rabbit, he also showed a fear response.
Discrimination
occurs when only the CS produces the CR. People and other organisms can learn to discriminate between similar stimuli if the US is consistently paired with only the CS.

Higher-order conditioning
occurs when a well-learned CS is paired with an NS to produce a CR to the NS. In this conditioning, the old CS acts as a UCS. Because the new UCS is not innate, the new CR is not as strong as the original CR. For example, if you taught your dog to salivate to a bell, then flashed a light just before you rang your bell, your dog could learn to salivate to the light without ever having had food associated with it.