Mental testing and machine intelligence: The Lashley-Hull debate

Abstract

Karl Lashley and Clark Hull had a long and unresolved controversy about the structure and function of the brain, its relationship to the mind, and the use of machine metaphors to explain intelligence. Though on the surface their debate was not about the relative importance of heredity or environment in determining intelligence and behavior, this is the subtext that ran through their exchanges. A determined hereditarian, Lashley was committed, both intellectually and institutionally, to the integration of biology and psychology. But Hull believed that environmentally‐shaped reflex connections underlay behavior and that this law made psychology the most basic of the social sciences.

The Lashley–Hull debate revisited.

“…and out of his conviction that intelligence is determined primarily by heredity. Weidman's (1994) reasoning requires close examination. Surveying the results of Lashley's brain ablation experiments with rats during the 1920s, she observed that even though the data themselves were much the same throughout that period, Lashley moved in 1926 from a reflex theory interpretation of his findings to one that argued against connectionism.…”

“…He also removed all traces of environmentalism from his writings.... My argument is that his underlying allegiance was to a hereditarian belief in the determination of intelligence, which was compatible with the behaviorism of the early twenties, but not with behaviorism when it evolved into environmentalism in the late twenties. Watson's "radical environmentalist" tract, which appeared in 1924, redefined behaviorism in the mid and late twenties, and lost followers like Lashley, who believed it had ceased to be a useful theory, (p. 167) Weidman's (1994) interpretation of Lashley's conversion from advocate to opponent of reflex theory and connectionism is provocative and, though it appears to square with some of the facts-for example, Lashley's well-known emphasis on the importance of heredity in determining behavior and intelligence-in too many other places it takes on water.…”

“…So if Watson's environmentalism, which was conspicuous in 1919, was instrumental in Lashley's taking an anticonnectionist stand in 1926, why did Lashley delay so long in doing so? Consider next Weidman's (1994) assertion that Lashley jettisoned the entire behaviorist system. The problem with this claim is that Lashley never took it on board in the first place (Bruce, 1986).…”

“…Lashley did not eliminate all traces of environmentalism from his articles because of Watson (Weidman, 1994). His empiricist account of generalization gradients (Lashley & Wade, 1946) is but one example; another is his essay on instinct (Lashley, 1938a) which, though it underscored the importance of innate mechanisms of behavior, nevertheless reserved a place for learning and stressed that environmental influences can change the character of instinctive responses and their adequate stimuli.…”

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Weidman (1994) claimed that "Karl Lashley and Clark Hull had a long and unresolved controversy about the structure and function of the brain, its relationship to the mind, and the use of machine metaphors to explain intelligence" (p. 162). The record contained in published articles and unpublished correspondence indicates otherwise.

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