• Choose a category
• All
• Classic-Fiction

By Root 823 0

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.

Classical Conditioning Paradigm and the Learning Curve

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.

Strength of Conditioning and Classical Aversive Conditioning

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