Karl Lashley

Photo of Karl Lashley

Karl Spencer Lashley (June 7, 1890 – August 7, 1958) was an American psychologist and behaviorist well-known for his contributions to the study of learning and memory. His work significantly influenced the understanding of the brain and its function in these processes, challenging the prevailing theories of his time.

Early Life and Education

Karl Lashley was born in Davis, West Virginia. He pursued his undergraduate degree at the West Virginia University, where he developed an interest in psychology. Lashley continued his education at the University of Pittsburgh, where he began his research in psychology. He earned his Ph.D. from Johns Hopkins University in 1914, where he worked under the guidance of John B. Watson, a pioneer of behaviorism.

Career and Research

After completing his doctorate, Lashley held various academic positions, including at the University of Minnesota, the University of Chicago, and finally at Harvard University, where he spent a significant part of his career.

Lashley's research focused on attempting to locate where learning and memory processes occur in the brain. He conducted extensive experiments, primarily on rats, to understand the relationship between brain lesions and their effects on maze learning. One of his most notable experiments involved teaching rats to find their way through a maze, then lesioning different parts of their brains to observe the effects on their memory and learning capabilities.

Through his experiments, Lashley proposed two principles that have had a lasting impact on neuropsychology and the study of the brain: the principles of mass action and equipotentiality. The principle of mass action suggests that the extent of learning and memory impairment is proportional to the amount of brain tissue destroyed, regardless of the location. The principle of equipotentiality suggests that within certain brain areas, any part of that area can perform the function of any other part of that area if it is damaged.

Legacy

Karl Lashley's work challenged the phrenology-based view that specific mental functions could be mapped to precise areas of the brain. Although later research, particularly in the field of neuroscience, has shown that certain functions can indeed be localized to specific regions, Lashley's principles of mass action and equipotentiality remain influential. They have contributed to the understanding that the brain is a complex and interconnected organ, where many processes involve multiple regions working in concert.

Lashley was also a mentor to many students who would go on to become influential in the field of psychology, including Donald O. Hebb, who further developed the concept of neural networks and brain plasticity.

Death and Honors

Karl Lashley passed away on August 7, 1958. Throughout his career, he received numerous accolades for his contributions to psychology and neuroscience, including the presidency of the American Psychological Association.

See Also

• Behaviorism
• Cognitive Psychology
• Neuropsychology