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Karl Lashley

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Karl Lashley

Known for
Karl Lashley A fun and easy way to remember 39Karl Lashley39 in

Notable awards
Fellow of the Royal Society (1951)Daniel Giraud Elliot Medal (1943)

brain Mechanisms and Intelligence: A Quantitative Study of Injuries to the Brain

August 7, 1958 (aged 68) Poitiers, France

June 7, 1890 (age 68), Davis, West Virginia

Karl Lashley 12.6.2016

Karl Spencer Lashley (June 7, 1890 – August 7, 1958) was a psychologist and behaviorist remembered for his contributions to the study of learning and memory. A Review of General Psychology survey, published in 2002, ranked Lashley as the 61st most cited psychologist of the 20th century.


Karl Lashley httpsuploadwikimediaorgwikipediaen33bPho


Early life and education

He was born on June 7, 1890 in the town of Davis, West Virginia. He was the only child of Charles and Maggie Lashley. He grew up in a middle-class family with a reasonably comfortable life. Lashley's father had a love of local politics and held various political positions. On the other hand, his mother was a stay at home mom and had a vast collection of books in the home. His mother would have women from the community come in and she would teach them various subjects. This is no doubt what gave Lashley his love of learning. Lashley has always held his family in high regard. He has been noted saying his father was a kind man. Lashley grew up being a very active boy, both physically and mentally. He was able to read by the age of four. His favorite thing to do as a child was to wander through the woods and collect animals, like butterflies and mice. Lashley spent most of his childhood alone. He did not have many friends. The reasons for his lack of friendships is unclear. In connection, with his love of learning and education, Lashley made an exceptional achievement. He graduated high school at age 14. He enrolled at West Virginia University, where he had originally decided to become an English major. He took a course in zoology, however, and decided to switch his major to zoology due to his interactions with a professor. When speaking of this professor, Lashley wrote "Within a few weeks in his class I knew that I had found my life's work". After obtaining his Bachelor of Arts at the West Virginia University, he was awarded a teaching fellowship at the University of Pittsburgh where he taught biology along with biological laboratories. While there he also carried out research which he used for his master's thesis. Once Lashley completed his master's degree, he studied at Johns Hopkins University, where he received his Ph.D. degree in genetics in June 1911. After obtaining his Ph.D. he became a professor at University of Minnesota, University of Chicago, and Harvard University.


There were three people in particular that significantly influenced Lashley’s life. The first was his mother Maggie Blanche Spencer. Maggie was a strong advocate of schooling and from an early age she encouraged Karl intellectually; as a result he was able to read at the age of four. The second influential person that came into Karl’s life was a professor at the University of West Virginia named John Black Johnston. Johnston was the teacher of the first zoology course that Lashley took and he led Lashley to understand what he wanted to do the rest of his life. Psychologist John B. Watson had the most influence on Lashley. Together the two conducted field experiments and studyed the effects of different drugs on maze learning of rats. The influence of Watson helped Lashley to focus on specific problems in learning and experimental investigation, followed by the cerebral location of learning and discrimination.

Lashley's career began with research concerning brain mechanisms and how they were related to sense receptors. He also conducted work on instinct as well as color vision. In addition he studied many animals and primates, which had always been an interest of his from the start of his freshmen year at college. Although Lashley studied many things, his most influential research centered around the cortical basis of learning and discrimination. Karl researched this by looking at the measurement of behavior before and after specific, carefully quantified, induced brain damage in rats. He trained rats to perform specific tasks (seeking a food reward), then lesioned specific areas of the rat cortex, either before or after the animals received the training. The cortical lesions 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 that they were 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 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 the 1950s two separate principles had grown out of Lashley's research and they were mass action and equipotentiality.

Lashley was originally in search of a single biological locus of memory or “engram” however he ended up disproving his own theory suggesting that memories were not localized in one part of the brain rather they were spread out through the cortex. As a result of this discovery, Lashley developed two separate theories, Mass action and Equipotentiality. Mass action refers to the idea that the rate, efficacy and accuracy of learning depend on the amount of cortex available. To be specific if cortical tissue is destroyed following the learning of a complex task, deterioration of performance on the task is determined more by the amount of tissue destroyed than by its location. Equipotentiality refers to the idea that one part of the cortex can take over the function of another part; within a functional area of the brain, any tissue within that area can perform its associated function. Therefore, to destroy a function, all the tissue within a functional area must be destroyed. If the area is not destroyed then the cortex can take over another part. These two principles grew out of Lashley’s research on the cortical basis of learning and discrimination.

Later life

In February 1954 while doing his teaching at Harvard, Lashley unexpectedly collapsed and was hospitalized. He was later diagnosed with hemolytic anemia and was put on a cortisone treatment. The Cortisone eventually began to soften his vertebrae, and as a result a splenectomy was performed. He was on the road to a full recovery until his trip to France with his wife Clair, where he once again unexpectedly collapsed, but this time to his death on August 7, 1958.


Lashley was elected to many scientific and philosophical societies, including the American Psychological Association (Council member 1926-1928; President, 1929), Eastern Psychological Association (President, 1937), Society of Experimental Psychologists, British Psychological Association (Honorary Fellow), American Society of Zoologists, American Society of Naturalists (President, 1947), British Institute for the Study of Animal Behavior (Honorary Member), American Society of Human Genetics, American Physiological Society, Harvey Society (Honorary Member), National Academy of Sciences (elected in 1930). In 1938, he was elected a Member of the American Philosophical Society, the oldest learned society in the United States, dating to 1743. Since 1957, the Society has awarded the annual Karl Spencer Lashley Award in recognition of work on the integrative neuroscience of behavior. In 1943 Lashley was awarded the Daniel Giraud Elliot Medal from the National Academy of Sciences. Lashley was also awarded honorary Doctor of Science degrees from the University of Pittsburgh (1936), the University of Chicago (1941), Western Reserve University (1951), the University of Pennsylvania; in 1953, Johns Hopkins University presented him with an honorary Doctor of Laws degree.

Notable publications

  • 1923 "The behavioristic interpretation of consciousness." Psychological Review
  • 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.
  • 1943 "Studies of Cerebral Function in Learning", Journal of Comparative Neurology vol. 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

    Karl Lashley Wikipedia