The American neuropsychologist Karl Spencer Lashley (1890-1958) demonstrated relationships between animal behavior and the size and location of brain injuries, summarizing his findings in terms of the concepts of equipotentiality and mass action.

Karl Spencer Lashley was born at Davis, W. Va., on June 7, 1890. Even as a child he was interested in animals, an interest which continued throughout his adult life. His mother, Maggie Lashley, encouraged him in intellectual pursuits. After studying at the University of West Virginia and then taking a master's degree in bacteriology at the University of Pittsburgh, Lashley did doctoral and postdoctoral research at Johns Hopkins University. While at Hopkins, he was influenced by the zoologist H. S. Jennings, the psychiatrist Adolf Meyer, and the psychologist John B. Watson, the father of behaviorism.

Lashley was at once an experimental researcher and a psychological theoretician. His investigations were published in the leading journals and proceedings...