Story of Psychology - Morton Hunt [174]
Two Great Neobehaviorists: Hull and Skinner
As the above experiments show, behaviorists were enlarging their theory and methodology far beyond Watson’s formulations. He had described behavior in simplistic terms as “the total striped and unstriped muscular and glandular changes which follow upon a given stimulus,”37 a view later dubbed “muscle-twitch psychology.” For a while, his followers stuck to this view; as one of them, Walter Hunter, wrote in 1928, “All behavior seems to be a combination, more or less complex, of the relatively simple activities of muscles and glands.”38
Yet to say anything meaningful about complex forms of behavior, it was necessary to see them intact, as acts with an identity and meaning. A bird building a nest is not just an organism responding to X number of stimuli with X number of reflexes; it is also a bird building a nest—an intricate kind of behavior with a goal. As one behaviorist, Edwin Holt, said in 1931, behavior is “what the organism is doing”—hunting, courting, and so on—an organized entity, and not merely the string of reflexes of which that entity is constructed, not just “an arithmetical sum, related only by the and or plus relation.”39
But Holt refused to attribute purpose to the creature itself; that would have implied the influence of a mind that looked ahead to the goal and set out to reach it. Rather, he ascribed the purposiveness of complicated behaviors to the process by which S-R units were combined: the creature’s seeking or avoiding, at each step, assembled S-R units in such a way that the assemblage appeared to be purposive behavior. It was a vague and unsatisfying formulation, but it went as far as any orthodox behaviorist could go.
A more important development was the neobehaviorist effort of Clark L. Hull (1884–1952) of Yale University to make behaviorism a quantitatively exact science modeled after Newtonian physics. Hull, who had started out to be a mining engineer, suffered an attack of polio and remained partly crippled. He switched to psychology, since it was less likely to involve heavy physical activity, but the engineering training carried over, and he set out to develop a kind of calculus of behaviorism. As he wrote in his autobiography:
[I] came to the definite conclusions around 1930 that psychology is a true natural science; that its primary laws are expressible quantitatively by means of a moderate number of ordinary equations; that all the complex behavior of single individuals will ultimately be derivable as secondary laws from (1) these primary laws together with (2) the conditions under which behavior occurs; and that all the behavior of groups as a whole, i.e., strictly social behavior as such, may similarly be derived as quantitative laws from the same primary equations.40
Hull’s central concept was a familiar one: behavior consists of sets or chains of linked habits, each of which is an S-R connection that developed as a result of reinforcement. This was his version of Thorndike’s Law of Effect. What was new about Hull’s work was his postulation of a number of factors, each of which, he held, enhances, limits, or inhibits the formation of such habits, and his development of equations by which one could calculate the exact effect of each of those factors.
They included the level of the creature’s drive (a hungry rat has a stronger drive to food than a sated rat); the strength of the reinforcement (expressed in such terms as “5 grams of a standard food”); the number of times a stimulus had been followed by reinforcement; the degree of “need reduction” achieved by each reinforcement; the degree of “drive reduction” (drives are fueled by needs) due to fatigue and the length of time between one trial and the next trial; and so on and on. As Edwin Boring