One of the trials of childhood is receiving numerous injections. You may have seen pictures of children crying before they receive their shot. This behavior is an excellent example of classical conditioning, which was discovered by the Russian physiologist Ivan Pavlov (1849-1936). Children have a response (crying) to a stimulus (the injection). On later occasions, they have a response (cry) at the sight of the stimulus (the needle), or perhaps at the sight of other factors associated with the stimulus (the person who gives the shot). Four steps in classical conditioning explain what happens here (Table 7-2). Classical conditioning refers to the pairing of a stimulus and a response.

B. F. Skinner (1904-1990) developed an explanation of learning that stressed the consequences of behavior—what happens after we do something is all important.

For example, imagine a 10-year-old with a sweet tooth. His father has constantly prodded him all summer to mow the lawn: “Do it today, do it before I get home, or else.” But his mother, with a shrewd understanding of human behavior, discovers that the local store carries ice cream bars that her son likes, but they are rather expensive. She promises him a package each week after he mows the lawn. By the end of the summer, the boy is cutting the grass on a regular basis with no threats, coercion, or scoldings. Skillful use of reinforcement greatly increased the desired behavior. Operant conditioning refers to how the consequences of a behavior increase or decrease the likelihood that the behavior will happen again.