ABSTRACT
Our general thesis is that psychological processes, involving interaction between the behavior of the individual and the environment, modify the behavioral repertoire throughout life. However, operant conditioning and classical conditioning, along with other psychological processes, are influenced by a range of biological factors. There are a variety of ways in which characteristics of the species of the individual, which in turn are determined by the evolutionary history of the species, affect the outcome of conditioning. Many of these effects can be described in terms of selectivity: there are predispositions for relationships between certain classes of responses and stimuli, rather than others, to affect subsequent behavior. These effects complicate our account of conditioning processes, because we cannot assume that all relationships between CS's and US's or responses and reinforcers will have identical outcomes, but we should not find them surprising. After all, conditioning processes have only evolved and persisted because they serve a variety of biological needs for many animal species: they enable food, shelter, mates, and the other necessities of life to be located and, as we shall see later, danger to be avoided. It turns out that they are designed through evolution so that relationships that are of biological importance, whether between events or between behavior and environmental events, are likely to modify subsequent behavior.
