Child and Young Adult Hull

¶ … child and young adult Hull was plagued by very poor health, and he had poor eyesight all his life. He lived all of his life as a handicapped individual. A severe case of polio at age 24 left him disabled in one leg and forced him to wear a heavy iron brace and to always walk with a cane. His father once tossed horseshoes with him behind his home and he said rather plaintively that horseshoes with his son was the first athletic event he had ever participated in and was his only athletic event. His family had very little money and he had to interrupt his education several times to do odd jobs to earn money for school. His odd jobs included teaching night school and tutoring. He studied mining engineering at the University of Wisconsin for a while, then switched to psychology and earned his Ph.D. In 1918. In his early years, he wanted to be an engineer, but after taking a few elective courses in Psychology, he fell in love with the field of Psychology and he decided to switch his major.

During college he was very proud of his dissertation because "it moved experimental psychology into the area of thought processes by investigating the learning of concepts" (Hilgard, 1987), and he became very disappointed when year after year no one paid attention to it. He worked very hard on his thesis. Other early works involved the effects of tobacco on human behavior and a survey of the literature on tests, assessments and measurements. He developed several methods of statistic analysis and invented an unique machine to calculate correlations. Intriguingly enough he investigated concept formation and also hypnosis and suggestibility. In 1927 he read about Mr.

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Pavlov's ideas and turned his focus to problems of conditioned reflexes and learning. His major books included: Principles of Behavior (1943) and A Behavior System (1952). He was very ill for many years while writing the latter book, and died before reading the galley proofs. He never saw the finished product.

After his contact with Mr. Pavlov, Hull's position soon became one of an uncompromising, radically behavioristic analysis. He read Isaac Newton's Principia (1697) to find out where his early efforts at theory had faltered. Any difference between psychology and physics, held Hull, is in degree and not in kind.

His very mature system of ideas left very little room for consciousness, purpose, or any other mentalistic notion. When he spoke of intervening variables they closely and specifically tied to objective stimuli and responses. He viewed all of human behavior as automatic and reducible to the language of physics. He constantly warned against giving subjective meanings to any behavior being observed. We mustn't anthropomorphistically think, for example, "If I were a rat, what would I do in this situation?" In 1943 he suggested that we should consider "the behaving organism as a completely self-maintaining robot, constructed of materials as unlike ourselves as may be."

Clark Hull's Ideas on Motivation and Behavior

Hull devoted the next 10 years of his life to the study of hypnosis and suggestibility, and in 1933 he published a book titled, Hypnosis and Suggestibility, while employed as a notable research professor at Yale University. Yale is where he developed

Clark Hull 3 his major contribution to Psychology, an elaborate theory of behavior based on Pavlov's laws of conditioning. Pavlov provoked Hull to become greatly interested in the problem of conditioned reflexes and learning. In 1943 Hull published a book called, Principles of Behavior, which presented a number of constructs in a detailed Theory of Behavior. He soon became the most cited psychologist in history.

Clark Hull believed that human behavior is a result of the constant interaction between the organism and its environment. The environment provides the stimuli and the organism responds, all of which is observable. However, there is a component that is not observable, the change or adaptation that the organism needs to make in order to survive within the environment. Hull explains, "when survival is in jeopardy, the organism is in a state of need (when the biological requirements for survival are not being met) so the organism behaves in a fashion to reduce that need" (Schultz & Schultz, 1987, p 238). Simply, the organism behaves in such a way that reinforces the optimal biological conditions that are required for survival.

Clark Hull was an objective behaviorist. He never considered the conscious, or any mentalistic notion. He made every attempt to reduce every concept to physical terms. He viewed human behavior as mechanical, automatic and cyclical, which could be reduced to the terms of physics. Obviously, he thought in terms of mathematics, and felt that behavior should be expressed according to these terms. "Psychologist must not only develop a thorough understanding of mathematics, they must think in mathematics" (Schultz & Schultz, 1987, p 239). In the early 1900s three specific methods were Clark Hull 4 commonly used by researchers. These methods were observation, systematic controlled observation, and experimental testing of the hypothesis. Hull believed that an additional method was needed, - The Hypothetico Deductive method. This involved deriving postulates from which experimentally testable conclusions could be deduced. These conclusions would then be experimentally tested.

Clark Hull viewed the drive as a stimulus, arising from a tissue need, which in turn stimulates behavior. The strength of the drive is determined upon the length of the deprivation, or the intensity / strength of the resulting behavior. He believed the drive to be non-specific, which means that the drive does not direct behavior, rather it functions to energize it. In addition this drive reduction is the reinforcement. Hull recognized that organisms were motivated by other forces or secondary reinforcements. " This means that previously neutral stimuli may assume drive characteristics because they are capable of eliciting responses that are similar to those aroused by the original need state or primary drive" (Schultz & Schultz, 1987, p 240). So learning must be taking place within the organism.

Hull's learning theory focuses mainly on the principle of reinforcement; when a S-R relationship is followed by a reduction of the need, the probability increases that in future similar situations the same stimulus will create the same prior response. Reinforcement can be defined in terms of reduction of a primary need. Just as Hull believed that there were secondary drives, he also felt that there were secondary reinforcements - " If the intensity of the stimulus is reduced as the result of a secondary

Clark Hull 5 or learned drive, it will act as a secondary reinforcement" (Schultz & Schultz, 1987, p 241). The way to strengthen the S-R response is to increase the number of reinforcements, habit strength.

Clark Hull's Mathematic Deductive Theory of Behavior relied on the belief that the link between the S-R relationship could be anything that might effect how an organism responds; learning, fatigue, disease, injury, motivation, etc. He labeled this relationship as "E," a reaction potential, or as sEr. Hull's goal was to make a science out of all of these intervening factors. He classified his formula:

sEr = (sHr x D. x K. x V) - (sIr + Ir) +/- sOr as the Global Theory of Behavior. Habit strength, sHr, is determined by the number of reinforces. Drive strength, D, is measured by the hours of deprivation of a need. K, is the incentive value of a stimulus, and V is a measure of the connectiveness. Inhibitory strength, sIr, is the number of non-reinforces. Reactive inhibition, Ir, is when the organism has to work hard for a reward and becomes fatigued. The last variable in his formula is sOr, which accounts for random error. Hull believed that this formula could account for all behavior, and that it would generate more accurate empirical data, which would eliminate all ineffective introspective methods within the laboratory (Thomson, 1968).

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Although Hull was a great contributor to psychology, his theory was criticized for the lack of generalizability due to the way he defined his variables in such precise quantitative terms. "Thus, Hull's adherence to a mathematical and formal system of theory building is open to both praise and criticism" (Schultz & Schultz, 1987, p 242).

Clark Hull's Theory

For about 20 years Clark Hull held a very dominant position in the history of American academic psychology. Vast numbers of experiments by experimental psychologists all across the country were carried out to confirm or challenge various details of his theoretical formulations. Then during the 1960s, almost as quickly as his ideas had come to dominate learning theory, they largely vanished from it. The conclusion became first inescapable and then widespread that the basic tack he was taking, that of trying to formulate a precise mathematical model which would identify just how much of behavior is due to what, was an impossible task even for the Norway rat in a T-maze, which was the dominant animal and environment in this research. For a human being it was not even conceivable.

In retrospect it is incredible how much time and energy went into this endeavor and how little came out of it.. Hull perhaps added somewhat more to our knowledge of the behavior of the rat than Titchener did to our understanding

Clark Hull 7 of human consciousness, but not much. His basic approach turned out to be, to use a precisely appropriate metaphor in his world of rats and mazes, a blind alley.

One of Hull's starting points was in noting that conditioning theory failed to deal convincingly with motivation. He was astute enough to recognize that motivation may be viewed as either a learned aspect of behavior (as Guthrie viewed it) or as a behavioral determinant independent of learning (as Tolman viewed it). Either way, it needed to be given greater importance. Hull drew on Freud's "instincts" as motivating forces, but changed the word to "drives" in his own formulations.

Late in his life and work, in 1952, even before the futility of his modeling endeavors became evident, Hull finally admitted that his system probably applied only to hungry rats.

INVESTIGATIVE STRATEGY

Clark Hull concluded that:

1. We should begin with specific testable postulates, even if based on minimal evidence. Then we derive concrete, empirically verifiable deductions from these and test them.

2. The task of a theorist is to formulate postulates so they will lead to unequivocal deductions.

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3. The worth of a theory resides in how much research it generates and how consistent with its thoretical deductions the findings are.

4. He was willing to put himself on the line with his predictions. His willingness to be wrong was a remarkable virtue. He was constantly revising his theories in light of empirical results.

These first four points represent Hull's most lasting contribution to experimental psychology. No one before Tolman and Hull was as careful, as sophisticated, or as precise in experimental design. Their research models of compared groups were later supplanted by other models, like Skinner's single-subject designs, but the sophistication in experimental design that grew out of their work outlived their research programs and is still a characteristic feature of American academic psychology.

Also part of Clark Hull's approach was:

5. In theorizing, a very heavy emphasis on intervening variables, cast in mathematical form.

6. Kenneth Spence was intimately associated with Hull throughout most of Hull's career. It was Spence who finally urged Hull to adopt Tolman's "intervening variable" concept and approach.

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DRIVE AND REINFORCEMENT

1. Drive is based on animal's need-state -- hunger, thirst, sexual arousal, pain, or whatever. Drive activates behavior -- any behavior.

2. Reinforcement occurs whenever the drive is reduced; leading to learning of whatever response solves the animal's problem. Thus the reduction in need serves as reinforcement and produces reinforcement of the response that leads to it.

3. Basic approach: need-related motivation, drive, and S-R learning are produced by (and only by) reinforcement. The S-R connection is called "Habit.":

4. Hull held that drives are substitutable in motivating behavior. If a hungry animal has learned a given response to get food, it should be easy to transfer the same response to get water. Early studies tended to confirm this motivation transfer, but more recent experiments have failed to find such motivation transfer when proper care is taken to use sources of drive that can be independently manipulated. It now appears that what happens with difference sources of drive is very unpredictable.

An alternative formulation was proposed by Miller & Dollard. Using a similar habit construct, they proposed that any strong stimulus can have motivating or drive properties without being tied to the needs of the organism.

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HABIT AND BEHAVIOR

1. Drive and habit act together to determine the strength of behavior. Thus the strength of behavior depends on both:

a. animal's motivation at time of testing b. amount of prior learning

Neither motivation nor prior learning alone will tell us what animal do.

2. Habit is built up as result of drive reduction

3. Habit strength depends on four different classes of independent variables:

a. Number of reinforced trials b. Magnitude of reward c. Immediacy or delay of reinforcement d. interval between CS onset and U.S..

4. Behavior can be characterized by both frequency and magnitude, and the two measures need not be correlated. There might be a very frequent response of low amplitude or a rare response of high amplitude.

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EVIDENCE REGARDING DRIVE REDUCTION

1. Habit is indeed built up as result of drive reduction.

2. Experimental work has shown that there are other variables. For example, Neal Miller carried out a series of studies showing that placing food directly in the stomach is reinforcing but food in the mouth is much more reinforcing. 3. Sheffield proposed that it is not drive or need reduction that constitutes reinforcement; but simply the occurrence of a consumatory response. A rat learns a response when this response lets it eat, mate, explore, etc.