Clark L. Hull

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Clark Leonard Hull (1884-1952) was an influential American psychologist and behaviorist who sought to explain learning and motivation by scientific laws of behavior. Born in Akron, New York, Hull obtained bachelor's and master's degrees from the University of Michigan, and in 1918 a PhD in from the University of Wisconsin. His doctoral research on "Quantitative Aspects of the Evolution of Concepts" was published in Psychological Monographs.

Hull conducted research demonstrating that his theories could predict and control behavior. His most significant works were the Mathematico-Deductive Theory of Rote Learning (1940), and Principles of Behavior (1943), which established his analysis of animal learning and conditioning as the dominant learning theory of its time. Hull is known for his debates with Edward C. Tolman.

In experimental psychology, he created the "hypothetic-deductive" systematic method, after the observation and elaboration of hypotheses. This method brought him precise definitions and conceptualised axioms which helped him develop his theories. He believed that behavior was a set of interactions between an individual and their environment. He analysed behavior from a perspect of biological adaptation, which is an optimization of living conditions through need reduction.

Hull is often credited with having begun the modern study of hypnosis. His work Hypnosis and Suggestibility (1933) was a rigorous study of the phenomenon, using statistical and experimental analysis. Hull's studies emphatically demonstrated once and for all that hypnosis had no connection with sleep ("hypnosis is not sleep, … it has no special relationship to sleep, and the whole concept of sleep when applied to hypnosis obscures the situation"). The main result of Hull's study was to rein in the extravagant claims of hypnotists, especially regarding extraordinary improvements in cognition or the senses under hypnosis. Hull's experiments did show the reality of some classical phenomena such as hypnotic anaesthesia and post-hypnotic amnesia. Hypnosis could also induce moderate increases in certain physical capacities and change the threshold of sensory stimulation; attenuation effects could be especially dramatic.

He died on May 10, 1952, in New Haven, Connecticut.