Clark L. Hull

Clark Leonard Hull
File:ClarkHull2.jpg Clark Leonard Hull
Born	24 May 1884 Akron, New York
Died	10 May 1952 New Haven, Connecticut
Nationality	American
Alma mater	University of Michigan
Scientific career
Fields	Psychologist

Clark Leonard Hull (May 24, 1884 – May 10, 1952) was an influential American psychologist who sought to explain learning and motivation by scientific laws of behavior. Hull is known for his debates with Edward C. Tolman. He is also known for his work in drive theory.

Hull spent the mature part of his career at Yale University, where he was recruited by the president and former-psychologist, James Rowland Angell. He performed research demonstrating that his theories could predict 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’s model is expressed in biological terms: Organisms suffer deprivation; deprivation creates needs; needs activate drives; drives activate behavior; behavior is goal directed; achieving the goal has survival value.

Background

Hull was born in Akron in western New York state. He studied math, physics, and chemistry, intending to become an engineer, but changed direction when he encountered the works of Watson and Pavlov. Hull obtained bachelor's and master's degrees from the University of Michigan, and in 1918 a PhD from the University of Wisconsin–Madison, where he also taught from 1916 to 1929. His doctoral research on "Quantitative Aspects of the Evolution of Concepts" was published in Psychological Monographs.

Formula to determine motivation

Hull's formula for determining motivation, was sEr = sHr * D such that:
sEr = excitatory potential (likelihood that the organism would produce response r to stimulus s),
sHr = habit strength (derived from previous conditioning trials),
D = drive strength (determined by, e.g., the hours of deprivation of food, water, etc. A variety of other factors were gradually added to the formula to account for results not included by this simple function. Eventually the formula became:

sEr = V x D x K x J x sHr - sIr - Ir - sOr - sLr

such that V is the stimulus.

Drive theory

Hull's emphasis was on experimentation, an organized theory of learning, and the nature of habits, which he argued were associations between a stimulus and a response. Behaviors were influenced by goals that sought to satisfy primary drives—such as hunger, thirst, sex, and the avoidance of pain.

Studies on hypnosis

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 demonstrated emphatically once and for all that hypnosis is not related to 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 examine the veracity of the apparently extravagant claims of hypnotists, especially regarding extraordinary improvements of cognition or the senses by hypnosis. Hull's experiments showed the reality of some classical phenomena such as mentally induced pain reduction and apparent inhibition of memory recall.

However, Hull's work indicated that these effects could be achieved without hypnosis being considered as a distinct state, but rather as a result of suggestion and motivation, which was a forerunner of the behavioural study of hypnosis. Similarly, moderate increases of certain physical capacities and changes to the threshold of sensory stimulation could be induced psychologically; attenuation effects could be especially dramatic. Hull is famous for his hypnotic induction method in which he would look at someone straight in the eyes until they were induced.

Recognition and death

Hull received the Warren Medal during 1945 from the Society of Experimental Psychologists. During 1929, he began employment with Yale University and retained it until his death. He died on May 10, 1952, in New Haven, Connecticut.

See also

• Drive theory
• The Logic of Modern Physics

External links

• "The Conflicting Psychologies of Learning: A Way Out", Clark L. Hull (1935), Psychological Review, 42, 491-516.
• Lemov, Rebecca (2005). World as Laboratory: Experiments with Mice, Mazes, and Men. New York: Farrar, Straus, and Giroux. Chapter 4.
• Deci, E. L., & Ryan, R. M. (1985). Intrinsic motivation and self-determination in human behavior. New York: Plenum.
• National Academy of Sciences Biographical Memoir