Chapter Summary Pavlov proposed that generalization is an automatic by-product of the conditioning process, whereas Lashley and Wade proposed that experience is necessary for typical gradients to occur. Each theory seems to be correct in some cases and wrong in others. Some experiments found that discrimination training was necessary before typical generalization gradients appeared. However, experiments on sensory deprivation supported Pavlov’s position by finding generalization gradients for color with birds that were raised in an environment with only one color. Another question is whether stimulus control is absolute or relational. Spence’s theory of absolute stimulus control can account for peak shifts in generalization gradients by assuming that an excitatory gradient develops around the S+ and an inhibitory gradient develops around the S–. However, this theory cannot explain results from the intermediate-size problem, which favor the position that animals can respond to relationships between stimuli. Other evidence also suggests that animals are capable of learning relational rules. Terrace developed an “errorless” discrimination training procedure, in which the S– is introduced very early in training, but under conditions in which the subject is not likely to respond to this stimulus. Errorless discrimination training has been successfully used in behavior-modification programs with children who have mental handicaps and with other populations. Concept formation occurs when individuals learn to treat one class of stimuli as positive and another class as negative. Studies with pigeons and other animals show that they can learn such categories as tree, water, and people. Humans can also learn equivalence sets, in which random stimuli are arbitrarily assigned to different categories. Some psychologists have proposed that only humans can learn such arbitrary categories, but others claim to have evidence that animals can also learn them. Stimulus control techniques are used in behavior modification when a desired response seldom occurs in the presence of the appropriate stimulus. For students who do poorly, a special location can be trained as a strong discriminate stimulus for study behavior. If a person’s insomnia is due to poor stimulus control, the person’s bed can be trained as a strong discriminative stimulus for sleeping.