The Story of Psychology (51 page)
Read The Story of Psychology Online
Authors: Morton Hunt
In consequence, much of the research conducted between 1920 and the 1960s dealt with minute, undeniably objective but not very enlightening topics. A few representative titles from the
Psychological Bulletin
and the
American Journal of Psychology
in 1935 were:
“Influence of Hunger on the Pecking Responses of Chickens”
“Comparison of the Rat’s First and Second Explorations of a Maze Unit”
“The Use of Maze-Trained Rats to Study the Effect on the Central Nervous System of Morphine and Related Substances”
“Differential Errors in Animal Mazes”
“Circuits Now Available for the Measurement of Electrodermal Responses”
Even when human beings were the experimental subjects, the topics and methods were constrained by behaviorist doctrine. Some typical titles from the
American Journal of Psychology
in 1935 were:
“The Reliability of the pH of Human Mixed Saliva as an Indicator of Physiological Changes Accompanying Behavior”
“A Comparison of the Conditioning of Muscular Responses Which Vary in Their Degree of Voluntary Control”
“Experimental Extinction of Higher Order Responses”
“The Galvanic Skin Reflex as Related to Overt Emotional Expression”
“Over-Compensation in Time Relationships of Bilateral Movements of the Fingers”
The authors of these and similar studies were not really interested in the pecking behavior of chickens or the pH of human saliva but in learning—the acquisition of behavioral responses to different kinds of stimuli. Learning was the central concern of American psychology during the behaviorist era, the assumption being that almost all behavior could be explained by S-R learning principles.
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An equally important assumption was that these principles held true of all sentient creatures, much as the principles of valence are true of all elements in chemical compounds. What one learned from chickens, cats, dogs, and especially rats applied to human beings.
Rats were the favorite experimental animal because they were relatively cheap, small, easy to handle, and fast-maturing. Countless thousands of them served the cause of research by learning to run mazes, operate levers or push buttons to get food, jump at doors of different colors, depress a bar to turn off an electric current that was making their feet tingle, and a host of other tasks. There was nothing frivolous about these experiments; they were aimed at the discovery of important universal laws of behavior. A few examples:
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—A rat is placed at the start of a simple maze that includes six choice points (each choice point is a T, one branch being a blind alley, the other an alley that continues) and ends at the goal box. The rat begins exploring and sniffing about, and runs a little; it goes into a blind alley, turns back and runs the other way, and after making three wrong choices and three right ones reaches the goal box— and is lifted out and, after a brief rest, put back in the start box. On its seventh run it finds a food pellet at the goal; the rat sniffs it, then bolts it down. Another rat gets the same training but without any food reward, not even on the final run.
For a week both rats get the same training every day. By the end of the week the first rat knows the route perfectly and races through the maze, making no mistakes; the second rat still makes as many errors as ever. But finally the second rat gets a food reward at the end of its run—and, remarkably, on the next trial makes no errors. It learned as much from one rewarded trial as the other rat learned in a week. The experiment demonstrates the operation of two principles:
reward produces learning
, exemplified by the first rat’s behavior; and
lacking reward, there may be latent learning
, exemplified by the second rat’s behavior. (Learning takes place in some sense when there is no reward but becomes activated as soon as a reward is associated with the “right” behavior.)
What has this got to do with human behavior? Any teacher can tell you. A child practicing drawing or any other skill may make little progress until the teacher has a moment to say something encouraging or complimentary; then, suddenly, the child shows improvement. Similarly, a novice at flying may make a dozen bumpy landings, finally “grease one in” half by accident, winning praise from his instructor, and from then on make landings as if he had at last “got the idea.”
—One at a time, a number of rats are put in the start box of a simple T-shaped maze. At the end of the right-hand branch is a white door behind which is a bit of cheese; at the end of the left-hand branch is a black door behind which is a metal grid floor that gives the rat’s feet a mild but unpleasant shock. The rats learn, after a while, to turn right and push through the white door. But once they’ve learned, the experimenter switches the situation. Now the white door and food are at the end of the left branch, the black door and electrified grid at the end of the right branch. The rats turn right, get shocked, and soon learn to turn to the left.
Once again the diabolic experimenter reverses things, but now the rats learn almost immediately; they have come to associate reward and punishment with the colors of the doors, not their direction. The experiment revalidates Pavlov’s principle of
discrimination
, the determination of the rewarding cue in a two-cue situation.
Does this apply to humans? Of course. A novice at gardening gets only a meager crop of tomatoes but sees that his neighbor, who plants a different variety in a sunnier location, gets a bumper crop. The novice tries the neighbor’s variety the next year; still no luck. He realizes that the number of hours of sunshine must be the critical factor, fells some trees to get more sunshine, and is successful.
—Another T-maze in which rats learn to turn to the right. This time there is no punishment for choosing the left branch but merely a lack of reward. Some rats are lucky; they find a reward every time they choose the right side. Others are unlucky; they find food there only once every four times. The unlucky rats learn far more slowly
than the lucky rats to choose the right-hand branch. The experiment demonstrates that
partial reinforcement
is less effective in learning than is continual reinforcement.
But now the experimenter changes things; there is no reward at either branch for either group. What happens? Oddly, the rats who had previously been lucky lose their conditioning rapidly and begin to alternate their choices, while the ones who were rewarded only every fourth time continue to choose the right branch for a long while. The experiment has demonstrated the
partial reinforcement effect:
the higher the creatures’ expectations, the more disruptive a change in the situation; with lower expectations, their learned behavior is more stable when change occurs.
A human analogue: A highly efficient employee has had a generous raise every year; in a year of poor income for the company, he gets only a modest raise, loses his drive, starts taking longer lunches, leaves promptly at 5:00 p.m., and calls in sick now and then. A less capable employee, who has only occasionally gotten a raise bigger than a cost-of-living adjustment, gets only a cola in the poor year; his commitment to his job is unaffected, because, not expecting much, he does not interpret the lack of bonus as a change in the system.
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,”
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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.”
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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.”
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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.
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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 later said, with consummate understatement, it was a “ponderous” theory.
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An example: By means of the following equation one can calculate the extent to which any given number of repetitions of a reinforced act increases the strength of the learned habit:
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The equation says that the strength of the learned habit depends on the number of reinforced trials (
N
), the relationship between the afferent and efferent nerve impulses in the specific act (
S
H
R
), the physiologically maximum strength of that particular habit (
M
) minus—well, it goes on and on.
Hull’s work was a major attempt to model neobehaviorist psychology on the physical sciences and thereby have it achieve intellectual respectability. His calculus of learning, appearing piecemeal during the 1930s and in systematic form in his
Principles of Behavior
(1943), was greatly admired and hugely influential. In the late 1940s and the 1950s thousands of master’s theses and doctoral dissertations were based on one or more of his postulates; he became the most frequently cited psychologist in the literature of psychological research and the leading figure in the psychology of learning.
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But during the 1960s, the unwieldiness of his theory and the dwindling of behaviorism’s status made Hull’s name and work fade rapidly from sight. By 1970 he was rarely quoted, and today there is virtually no research based on his theory. When Hull died, in 1952, he seemed assured of scientific immortality; now he is a figure of minor historical interest, and few young psychologists and very few people outside the profession know his name.
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B. F. Skinner (1904–1990), another leading neobehaviorist, had a very different fate. He became, and remained until his death at eighty-six, the best-known psychologist in the world,
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and his ideas are in wide use today in psychological research, education, and psychotherapy.
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