Roger W. Sperry (1913-1994)
Roger Wolcott Sperry was born in a small suburb of Hartford, Connecticut in 1913. He spent a total of seven years at Oberlin College in Ohio; there he received both a Bachelor of Arts in English in 1935, and a Master’s Degree in Psychology in 1937. His final year was spent at-large preparing to begin work on a Ph.D. in Zoology. He moved to Illinois and in 1941, received his Ph.D. from the University of Chicago under Professor Paul A. Weiss. Afterward, Sperry did one year of postdoctoral research under Professor Karl Lashley at Harvard University. He went on to do further research at other institutions. Between 1952 and 1954, he became Associate Professor of Psychology at the University of Chicago, Section Chief of Neurological Diseases and Blindness at the U.S. National Institutes of Health, and Professor of Psychobiology at California Institute of Technology. With David H. Hubel and Torsten N. Weisel, he won the Nobel Prize in Physiology or Medicine in 1981. This was one of thirty-four awards he won in his lifetime. Sperry retired in 1984 in Pasadena, California, where he had lived for thirty years by that time. He died from complications with ALS in 1994.
Theories |
Chemoaffinity Hypothesis (1960s): neurons make connections with targets based on interactions with molecular markers (sections of DNA associated with particular genome locations) that are generated during cellular differentiation. This means that the wiring diagram of an organism’s nervous system is dictated by its genotype.
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Most Famous Experiment |
Roger Sperry is most well known for his split-brain research, which was conducted in the 1950s and 60s at the California Institute of Technology. Sperry found that the two halves, or hemispheres, of the brain performed different tasks. Severing the corpus callosum (the bundle of neurons that connects the halves) caused the two hemispheres to function separately. Cats, frogs, and monkeys were some of the animals used in split-brain experiments. “The Split Brain in Man,” an experiment conducted by Sperry and Michael Gazzaniga, is the most famous study done with people who had undergone a corpus callosotomy.
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Aim: To determine the extent to which the two hemispheres of the human brain could function independently.
Independent Variable: The subjects’ state of being “split-brain”
Dependent Variable: How the subjects processed the information presented
Methods: Four people who had undergone a corpus callosotomy to stop seizures participated in these experiments. Sperry and Gazzaniga conducted three tests: visual, tactile, and a combination of the two.
1. In the visual test, a subject would sit in front of a horizontal board of lights and stare at a point in the middle of the board. Specific lights would flash, and then the subject would be asked to describe what they saw. Later, they were asked to point at the lights that had flashed.
2. In the tactile test, an object would be placed in one of the subject’s hands. The subject would be asked to describe and name the object. Later, the subject would be asked to choose the one they had held from a group of other similar objects.
3. In the combination test, an image of an object was shown to the right hemisphere of a subject, and they were asked to describe the object in the image. If they could not, they would be allowed to feel several objects with their left hand without looking and choose the correct one.
Results:
1. When the lights flashed across both the left and right sides of the board, subjects reported that only the lights on the right side had flashed. When only lights on the left side of the board flashed, subjects said that they did not see any lights. However, when the subjects were told to point at the lights that had flashed, they pointed at lights on both the left and right sides.
2. When an object was placed in the right hand, subjects could describe and name it. When it was placed in the left hand, they could not. However, they COULD match the object correctly.
3. Subjects could not verbally describe the object in the image, but they could choose the correct object with their left hand without looking.
Significance: Sperry and Gazzaniga found that the two hemispheres of the brain perform different functions, and if they are severed, it can be impossible for certain information to be communicated between the halves. For example, when an object was placed in the left hand of a subject, it could not be described or named even though the subject knew what it was. This is because language functions are located in the LEFT hemisphere of the brain, and the left hemisphere controls the RIGHT side of the body. These experiments helped Sperry to determine which skills and functions were present in each side of the brain.
Independent Variable: The subjects’ state of being “split-brain”
Dependent Variable: How the subjects processed the information presented
Methods: Four people who had undergone a corpus callosotomy to stop seizures participated in these experiments. Sperry and Gazzaniga conducted three tests: visual, tactile, and a combination of the two.
1. In the visual test, a subject would sit in front of a horizontal board of lights and stare at a point in the middle of the board. Specific lights would flash, and then the subject would be asked to describe what they saw. Later, they were asked to point at the lights that had flashed.
2. In the tactile test, an object would be placed in one of the subject’s hands. The subject would be asked to describe and name the object. Later, the subject would be asked to choose the one they had held from a group of other similar objects.
3. In the combination test, an image of an object was shown to the right hemisphere of a subject, and they were asked to describe the object in the image. If they could not, they would be allowed to feel several objects with their left hand without looking and choose the correct one.
Results:
1. When the lights flashed across both the left and right sides of the board, subjects reported that only the lights on the right side had flashed. When only lights on the left side of the board flashed, subjects said that they did not see any lights. However, when the subjects were told to point at the lights that had flashed, they pointed at lights on both the left and right sides.
2. When an object was placed in the right hand, subjects could describe and name it. When it was placed in the left hand, they could not. However, they COULD match the object correctly.
3. Subjects could not verbally describe the object in the image, but they could choose the correct object with their left hand without looking.
Significance: Sperry and Gazzaniga found that the two hemispheres of the brain perform different functions, and if they are severed, it can be impossible for certain information to be communicated between the halves. For example, when an object was placed in the left hand of a subject, it could not be described or named even though the subject knew what it was. This is because language functions are located in the LEFT hemisphere of the brain, and the left hemisphere controls the RIGHT side of the body. These experiments helped Sperry to determine which skills and functions were present in each side of the brain.
