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Karl Lashley
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| Biography: Karl Spencer Lashley |
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 of major scientific societies. After several joint studies with Jennings, Lashley published his own thesis, "Inheritance in the Asexual Reproduction of Hydra. …" He collaborated with Watson in studying behavior in seabirds, acknowledging Watson's behavioristic approach the rest of his life.
Collaborating with Shepherd Ivory Franz, Lashley produced several papers on the effects of cerebral destruction upon retention and habit formation in rats. This was the beginning of his preoccupation with one of the persistent problems in psychology, that of cerebral localization. Earlier researchers Gall, Broca, Fritsch and Hitzig, Ferrier, and Munk were all believers in exact cerebral localization, whereas Flourens, Goltz, and Franz doubted it. The culmination of his localization experiments was Brain Mechanisms and Intelligence: A Quantitative Study of Injuries to the Brain (1929), his longest, most significant monograph. In it he summarized his concepts of equipotentiality and mass action and marshaled the experimental evidence to support them. Thus he accounted for the absence of precise and persistent localization of function in the cortex. Lashley's experiments denied the simple similarity and correspondence, previously assumed, between associationistic connectionism and the neuronal theory of the brain as a mass of neurons connected by synapses.
In addition to his researches Lashley taught as professor of psychology at the universities of Minnesota and Chicago and at Harvard University. He held various honorary positions and lectureships, was on the editorial boards of numerous scientific journals, served as member of and adviser to governmental committees, and was elected to many scientific and philosophical societies. He died on Aug. 7, 1958, in Poitiers, France.
Further Reading
An enjoyable biographical narrative of Lashley's life and work by Frank A. Beach, Karl Spencer Lashley (1961), includes a chronological bibliography of his writings. Lashley's contributions to psychological literature are representatively sampled in a collection, The Neuropsychology of Lashley, edited by Frank A. Beach (1960), which includes as an introduction a penetrating evaluation by Edwin G. Boring, as well as an appreciation by the neurologist Stanley Cobb.
| Medical Dictionary: Lash·ley |
(lăsh'lē), Karl Spencer 1890–1958.
American neuropsychologist known for his contributions to the study of localization of brain functions.
| World of the Mind: Karl Spencer Lashley |
(1890–1958). American neuropsychologist, educated at Johns Hopkins University, Baltimore. While still relatively junior he began to work with Shepherd Ivery Franz, a pioneer in the application of physiological methods to the study of brain mechanisms and intelligence in animals. Lashley later worked closely with J. B. Watson and may be regarded as a co-founder of behaviourism. Indeed his understanding of neurology was a good deal more sophisticated than that of Watson and he soon abandoned Watson's reliance on reflexes and conditioned reflexes (see conditioning) as the building blocks of behaviour. At the same time, he held strongly to Watson's insistence on objective methods and the abandonment of consciousness in the explanation of behaviour.
Lashley's best-known work involved study of the effects of lesions of the cerebral cortex on intelligence and learning in the rat and monkey. He was a most competent experimenter and the first to apply statistical methods to the analysis of the results of brain lesions and to ascertain their locus and extent by post-mortem anatomical study. He published two influential groups of studies, the first concerned with cerebral function in learning (1920–35) and the second on the neural mechanisms of vision (1930–48). His monograph Brain Mechanisms and Intelligence appeared in 1930.
Lashley's work convinced him that, although sensory and motor functions are in some sense localized, the effects of cerebral lesions involving the so-called association areas do not indicate clear-cut functional localization, but rather as he thought 'mass action' such that loss of complex skills was a function of the volume of excised brain rather than its location. With later, more sophisticated experiments, this view is greatly modified in favour of specific regions of specialized functions. Lashley was a figure of high standing in the field of physiological psychology and although, unlike his early colleague Franz, he never extended his studies to brain injury in man, he had great influence on the evolution of contemporary neuropsychology. Among his students were Donald O. Hebb and Karl Pribram. He was a Foreign Fellow of the Royal Society of London.
(Published 1987)
Lashley's best-known work involved study of the effects of lesions of the cerebral cortex on intelligence and learning in the rat and monkey. He was a most competent experimenter and the first to apply statistical methods to the analysis of the results of brain lesions and to ascertain their locus and extent by post-mortem anatomical study. He published two influential groups of studies, the first concerned with cerebral function in learning (1920–35) and the second on the neural mechanisms of vision (1930–48). His monograph Brain Mechanisms and Intelligence appeared in 1930.
Lashley's work convinced him that, although sensory and motor functions are in some sense localized, the effects of cerebral lesions involving the so-called association areas do not indicate clear-cut functional localization, but rather as he thought 'mass action' such that loss of complex skills was a function of the volume of excised brain rather than its location. With later, more sophisticated experiments, this view is greatly modified in favour of specific regions of specialized functions. Lashley was a figure of high standing in the field of physiological psychology and although, unlike his early colleague Franz, he never extended his studies to brain injury in man, he had great influence on the evolution of contemporary neuropsychology. Among his students were Donald O. Hebb and Karl Pribram. He was a Foreign Fellow of the Royal Society of London.
(Published 1987)
— O. L. Zangwill/Richard L. Gregory
- Bibliography
- Beach, F. A., Hebb, D. O., and Morgan, C. T. (eds.) (1960). The Neuropsychology of Lashley.
- Orbach, J. (1982). Neuropsychology after Lashley.
| Wikipedia: Karl Lashley |
| Karl Spencer Lashley | |
|---|---|
| Born | June 7, 1890 Davis, West Virginia |
| Died | August 7, 1958 |
| Nationality | United States |
| Fields | psychology |
| Alma mater | Johns Hopkins University |
| Known for | learning and memory |
Karl Spencer Lashley (1890–1958), born in Davis, West Virginia, was an American psychologist and behaviorist well-remembered for his influential contributions to the study of learning and memory. His failure to find a single biological locus of memory in the rat's brain (or "engram", as he called it) suggested to him that memories were not localized to one part of the brain, but were widely distributed throughout the cortex.
While working toward his Ph.D. in genetics at Johns Hopkins University, Karl Lashley became associated with the influential psychologist John B. Watson. During three years of postdoctoral work on vertebrate behavior (1914-17), he began formulating the research program that was to occupy the remainder of his life.
In 1920 he became an assistant professor of psychology at the University of Minnesota, Minneapolis, where his prolific research on brain function gained him a professorship in 1924. He was later a professor at the University of Chicago (1929-35) and Harvard University (1935-55) and also served as director of the Yerkes Laboratories of Primate Biology, Orange Park, Florida from 1942 to 1955.
His work included research on brain mechanisms related to sense receptors and on the cortical basis of motor activities. His major work was done on the measurement of behavior before and after specific, carefully quantified, induced cortical damage in rats. He trained rats to perform specific tasks (seeking a food reward), then lesioned varying portions of the rat cortex, either before or after the animals received the training depending upon the experiment. The amount of cortical tissue removed had specific effects on acquisition and retention of knowledge, but the location of the removed cortex had no effect on the rats' performance in the maze. This led Lashley to conclude that memories are not localized but widely distributed across the cortex. Today we know that distribution of engrams does in fact exist, however, the distribution is not equal across all cortical areas, as Lashley assumed. His study of the V1 (primary visual cortex) led him to believe that it was a site of learning and memory storage (i.e an engram) in the brain. He reached this erroneous conclusion due to imperfect lesioning methods.
By 1950, Lashley had distilled his research into two theories. The principle of "mass action" stated that the cerebral cortex acts as one—as a whole—in many types of learning. The principle of "equipotentiality" stated that if certain parts of the brain are damaged, other parts of the brain may take on the role of the damaged portion.
Contents |
Notable publications
- 1923 "The behavioristic interpretation of consciousness." Psychological Bulletin
- 1929 "Brain mechanisms and intelligence."
- 1930 "Basic neural mechanisms in behavior." Psychological Review
- 1932 "Studies in the dynamics of behavior." University of Chicago Press.
- 1935 "The mechanism of vision", Part 12: Nervous structures concerned in the acquisition and retention of habits based on reactions to light. Comparative Psychology Monographs 11: 43–79.
- 1950 "In search of the engram." Society of Experimental Biology Symposium 4: 454–482.
- 1951 "The problem of serial order in behavior." Cerebral Mechanisms in Behavior
References
- Dewsbury, Donald A (2002), "Constructing representations of Karl Spencer Lashley.", Journal of the history of the behavioral sciences 38 (3): 225–45, doi:, PMID 12115785
- Dewsbury, D A (2002), "The Chicago Five: a family group of integrative psychobiologists.", History of psychology 5 (1): 16–37, 2002 Feb, doi:, PMID 11894885
- Sapetskiĭ, A O, "[A physiologist's dialog with a psychologist]", Zhurnal vyssheĭ nervnoĭ deiatelnosti imeni I P Pavlova 49 (6): 909–18, PMID 10693270
- Bruce, D (1986), "Lashley's shift from bacteriology to neuropsychology, 1910-1917, and the influence of Jennings, Watson, and Franz.", Journal of the history of the behavioral sciences 22 (1): 27–44, 1986 Jan, doi:, PMID 3511136
- Roofe, P G (1970), "Some letters from the Herrick-Lashley correspondence.", Neuropsychologia 8 (1): 3–12, 1970 Jan, doi:, PMID 4941968
- CARMICHAEL, L (1959), "Karl Spencer Lashley, experimental psychologist.", Science 129 (3360): 1410–2, 1959 May 22, doi:, PMID 13658968
- WALSHE, F M (1958), "Karl S. Lashley.", Neurology 8 (11): 870, 1958 Nov, PMID 13590401
- Weidman, Nadine (2002), "The depoliticization of Karl Lashley: A response to Dewsbury.", Journal of the history of the behavioral sciences 38 (3): 247–53; discussion 255–7, doi:, PMID 12115784
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