mass action

Karl S. Lashley’s generalization that the size of a cortical lesion, rather than its specific location, determines the extent of any resulting performance decrement. Proposed in 1929 following experimental observations of the effects of different brain lesions on rats’ ability to learn a complex maze, the concept reflects Lashley’s belief that large areas of the cortex function together in learning and other complex processes. This concept is no longer considered completely valid. Also called law of mass action; principle of mass action. See also equipotentiality.

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Psychology term of the day

January 5th 2025

head-of-the-table effect

the propensity for group members to associate the leadership role and its responsibilities with the seat located at the head of the table. As a result, individuals who occupy such positions tend to emerge as leaders in groups without designated leaders. See also Steinzor effect.