Roger Sperry

Would you believe there was so much we still did not know about the brain and its functions in the 1960s? There was still so much information to uncover, and one notable researcher in psychology, Roger Sperry, helped answer many of those questions. One of his questions about the brain sounds crazy! "Would the brain still work if we split it in half?" These sound like the words of a crazy scientist, but they were incredibly helpful in understanding the brain. 

Roger Sperry Roger Sperry

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Table of contents
    • Who was Roger Sperry in the field of Psychology?
    • What experiment did Roger Sperry and Michael Gazzaniga conduct?
    • What split-brain experiments did Roger Sperry conduct?
    • What were the effects of the split-brain experiments?

    Roger Sperry's Contribution to Psychology

    Roger Sperry was most notably interested in the brain's functions and would often experiment on monkeys, cats, and even humans. As you continue reading, you will see that Sperry was interested in the workings and functions of the corpus callosum but did not stop at this area of the brain.

    Roger Sperry, a photo of Roger Sperry, StudySmarter

    Roger Sperry, wikimedia.commons.org

    In the 1960s, Roger Sperry theorized about the chemicals and axons in the brain. This theory was known as Sperry's chemoaffinity hypothesis. Sperry asked, "how do chemicals reach certain organs of the body?" He also asked, "what chemicals are being used for certain organs?"

    The chemoaffinity hypothesis states that each neuron has its own chemical identity that directs its synapse to the proper target cell during development.

    Sperry wanted to understand how the nervous system could develop from a group of individual nerves within the body. Through experiments and scientific procedures, Sperry revealed a strange discovery about the brain.

    Sperry liked to use all kinds of volunteers in his research, and his experiments often included monkeys, cats, frogs, and humans.

    Roger Sperry and Michael Gazzaniga

    In the 1960s, Sperry and Michael Gazzaniga conducted experiments with the assistance of a participant with epilepsy who had undergone brain surgery to treat his seizures. The surgery involved cutting the participant's corpus callosum in half to cut the connection between the two sides of the brain.1 After this procedure, the participant seemed to act normally, but they soon realized that it was difficult for him to name objects.

    Sperry and Gazzaniga also gave the participant blocks to assemble with particular directions, which was also difficult for him. After repeated attempts at naming objects and using the blocks, the researchers realized that some tasks were more difficult depending on the instructions they gave the participant.

    The researchers discovered that the left hemisphere of the brain (the left side) is responsible for processing language (the meaning of words), and the right side is responsible for processing visual construction tasks.

    Roger Sperry Split-Brain Experiments

    The corpus callosum interested Sperry for many reasons. How did Sperry use this area of the brain for experiments?

    The corpus callosum is a bundle of nerve fibers that connects the two sides of the brain like a telephone wire sending messages back and forth.

    Sperry cut the corpus callosum in cats and monkeys to study the function of each side of the brain. He discovered that when the hemispheres are disconnected, they function independently of one another. Sperry called this a split-brain. This research technique is now known as a split-brain procedure or split-brain research method.

    Roger Sperry, Illustration of a brain split in half, StudySmarterSplit-brain, flaticon.com

    The split-brain procedure enabled the cats and monkeys to memorize double the information!

    Sperry used different test subjects, and he learned new information from each of them. What did Sperry learn from his research with monkeys, cats, and humans?

    Sperry's Cats

    What about his cat subjects? What new information did Sperry uncover in these experiments? The split-brain cats had one eye closed while Sperry showed them two different blocks. One block had food underneath it, and the other had nothing under it. Once Sperry showed these items to the cats, he would then cover the other eye and switch the food to the other block.

    Did this confuse the cats? Sperry noticed that the cats only remembered the events as separate occurrences. The cats could not tell the difference between the blocks when both of their eyes were later uncovered. After uncovering, the cats were unsure which block to choose and ultimately just chose each block an equal number of times.

    Sperry thought that, from the experiment's results, the right eye connected to the left hemisphere and the left eye connected to the right hemisphere. Since Sperry had cut the corpus callosum, the cat's hemispheres could not talk to each other. Sperry realized that when the cat's hemispheres were disconnected from each other, information from each eye only went to one hemisphere or side of the brain. That hemisphere was able to remember which block had food underneath it.

    Right eye = left hemisphere, and left eye = right hemisphere

    Sperry thought that the cats could technically have two differently functioning brains because the hemispheres could not speak with each other. Each hemisphere worked as if the other one did not even exist! Were there any discoveries when the corpus callosum was cut in the brains of monkeys?

    Sperry's Monkeys

    When Sperry experimented on monkeys (the corpus callosum of the monkeys was severed or cut), he made them use both of their eyes simultaneously by using special light filters and projectors. What did Sperry discover? The split-brain monkeys could remember two different scenarios at the same time as another monkey (with no cut in the brain) was only able to memorize one.

    What did this demonstrate? The monkey with a severed corpus callosum had brain hemispheres that could not communicate with each other. Therefore, each hemisphere acted as a separate brain!

    Sperry's Human Participants

    For the humans with a severed corpus callosum, Sperry would cover one of their eyes. He would then show a word to the uncovered eye, but the participant could only remember seeing the word if Sperry held it up to the right eye.

    Remember! Right eye = left side of the brain.

    With this information, Sperry then showed one object to the right eye and another to the left eye. After this, Sperry asked the volunteers to draw what they had seen. What did Sperry learn from this?

    Roger Sperry, a drawing of a human participant in a split-brain research study, StudySmarterSplit-brain research, wikimedia.commons.org

    Sperry's research showed that the left hemisphere of the brain could understand and recognize speech, while the right hemisphere was not able to do so.

    This new discovery was essential to science and psychology at the time. Before this, scientists had no idea which side of the brain was best for doing certain functions and tasks or if each hemisphere could perform the same tasks.

    Split-Brain Surgery Effects

    Of course, permanently changing the brain can have major effects. What happens to the brain after split-brain surgery? Sperry noticed that after each split-brain surgery, no major complications occurred in the patient, including both mental and physical capacities. The only major difference was that the brain began acting like the two hemispheres were entirely separate brains. The left hemisphere acted as if the right hemisphere was not present and vice versa.

    Roger Sperry - Key takeaways

    • In the 1960s, Roger Sperry theorized about the chemicals and axons that were in the brain. This theory is known as Sperry's chemoaffinity hypothesis.
    • In the 1960s, Sperry and Michael Gazzaniga conducted experiments with the assistance of a participant with epilepsy who had undergone brain surgery to treat his seizures.
    • Sperry cut the corpus callosum in the brain of cats and monkeys to study the function of each side of the brain. He discovered that when the hemispheres are not connected, they function independently of one another. Sperry called this a split-brain.
    • The only major difference was that the brain began acting like the two hemispheres were entirely separate brains. The left hemisphere acted as if the right hemisphere was not present and vice versa.
    • The left hemisphere of the brain (the left side) is responsible for processing language (the meaning of words), and the right side is responsible for processing visual construction tasks.

    References

    1. PBS. (1998). A Science Odyssey: People and Discoveries: Roger Sperry. Retrieved June 29, 2022, from https://www.pbs.org/wgbh/aso/databank/entries/bhsper.html
    Frequently Asked Questions about Roger Sperry

    What was Roger Sperry's contribution to psychology?

    Roger Sperry's contributions to psychology included his chemoaffinity hypothesis and split-brain theory.

    What field of psychology did Roger Sperry study?

    Roger Sperry studied neurology in psychology as shown in his split-brain theory.

    What is the split brain theory?

    The split brain theory is the theory that each side or hemisphere of our brain has its job to complete. The left hemisphere was in charge of language processing, and the right side was responsible for tasks of visual construction (understanding what we see).

    Why is split brain important?

    Split brain theory is important because there was no understanding of which side of the brain was the best for doing certain functions and tasks or if each hemisphere could act independently.

    What did Roger Sperry discover?

    Roger's experiments showed us that each side or hemisphere of our brain has its job to complete. The left hemisphere was in charge of language processing, and the right side was responsible for tasks of visual construction (understanding what we see).

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