Drive, incentive, and reinforcement: the antecedents and consequences of motivation.

The aim of scientific explanation is to characterize the important antecedents of observable (or at least objectively confirmable) events. Explanations of behavior in terms of motivational states are appeals to unobservable, internal events for interpretations of behavior that is variable under apparently constant external stimulus conditions (see, e.g., Brown, 1953; Hinde, 1960). To be identified as the cause of a behavior, the unobservable event or condition must preexist the behavioral event to be explained. A behavior cannot be explained by its consequences, though it may be explained as a consequence of similar events in the animal's history. Scientific explanation involves the sequential identification of what comes first and what follows. To understand correctly what comes first and what follows is to achieve the primary goal of science. While the teleology of Aristotle's notion of "final causes" encouraged the explanation of what comes first by what comes after, the major advance of the scientific revolution was to substitute mechanical causes-necessary and sufficient conditions (the "efficient causes" of Aristotle)-for the "final causes II previously legitimized by Aristo-tle's teachings (see Aristotle, Physics, in Barnes, 1984). Galileo precip-I thank Leon Brown, Satoshi Ikemoto, Yavin Shaham, and Abraham Zangen for in-sightful comments on earlier versions of this chapter. itated the culling of Aristotelean teleology from physics; we no longer accept Aristotle's notion that heavy things fall faster than light ones or his teleological suggestion that they do so "in order to reach their natural place." Two centuries after Galileo, Darwin (1859) offered a nonteleological explanation for human evolution; his principles of random mutation and natural selection offered a mechanistic alternative to the Aristotelean notion that human evolution was partly determined by the goal or intention of a creator. Skinner's (1966) parallel suggestion that behavior is generated randomly and selected by its consequences was an attempt to go beyond the rigidity of reflexes while avoiding the teleology inherent in the notion of goal direction. The apparent goal direction of motivated behavior explains nothing; it is the mystery that remains to be explained. The problem of teleology is the problem of suggesting a consequence something that follows-as the explanation of its cause-something that came first. A major challenge for psychology is to find mechanistic alternatives to teleological explanations of behavior. For psychology to advance our understanding of behavior within the scientific paradigm it must find the efficient causes-the necessary and sufficient antedating conditions-for behaviors that appear to …