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Michael Gazzaniga

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Michael Gazzaniga conducted several experiments on split-brain patients that showed the independence and specialized functions of the left and right hemispheres. His experiments demonstrated that each hemisphere can act independently, with the right hemisphere specialized for nonverbal tasks and the left hemisphere acting as an "interpreter" for conscious experience. Further experiments revealed the right hemisphere's capacity for perceptual grouping and ability to process images holistically compared to the left hemisphere's tendency to form theories and analyze patterns. Gazzaniga's work was influential in establishing the concept of lateralization of brain function between the two hemispheres.

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Michael Gazzaniga Helena Yeung and Brian Zhao
Background Born on December 12, 1939 Graduated from Dartmouth College in 1961, received his Ph.D at Cal Tech in 1964 Worked under Sperry as a his prot辿g辿 Sperry was a pioneer of human split-brain research Theories regarding functional lateralism in the brain had already been established
Findings (split hemispheres) 1967 Experiment on split-brain patients Concluded that split-brain patients possessed two hemispheres that acted independently
Findings (nonverbal right hemisphere) 1967 Experiment in split-brain patients Flashed a picture of spoon to participants right hemisphere Asked participant to identify the object: participants generally replied with I dont know. Asked participant to choose the object from a pile of objects: participants would generally choose correctly. Concluded that the right hemisphere in split-brain patients was nonverbal
Findings (isolated hemispheres) Case study: WJ (epileptic patient with split-brain) Held apple to WJs right eye, and WJ would say, I see an apple Held apple to WJs left eye, and WJ would say, I dont see anything, but would be able to pick out a pictorial representation w/ left hand Concluded that two hemispheres of the split brain do not communicate with each other
Findings (the interpreter) Gazzaniga labeled the left hemisphere as the brains interpreter (1998) Researchers noticed that, when information is sent to the right-hemisphere to control the left hand, the left hemisphere, when it sees this, interprets this event, and consolidates it with its ongoing mental monologue Gazzaniga proposed that the left hemisphere rationalizes the actions, protecting the holistic nature of the individuals mind, giving the individual a sense of self
Findings (the gist capacity) Experiment: participants were asked to bet on which of two events would occur, one having an 80% chance of occurring, and the other having a 20% chance of occurring. Instead of choosing the event that repeatedly occurred, humans often attempted to discern patterns within the frequency of the events A rat would lose less money than a human through the same process, as they rely more on the right hemisphere Concluded that right brain takes events and images at face value, while the left brain made theories.
Findings (right hemisphere) Perceptual grouping: You know that a specific object is at the bottom of a pile, and you go directly for it, without searching You see a deer in the woods; you can only see parts of the deer, but your brain mentally puts the missing pieces together
Methodology Experiments: Performed on patients who had undergone split-brain procedures Studied with an apparatus that took advantage of separate visual fields If a split-brain patient is seated in front of a screen and told to look at an X in the middle of the screen, and if the picture is flashed on the screen too quickly for an eye movement to occur, then everything to the left of the X will go to the right hemisphere. Everything to the right of the X will go to the left hemisphere Displayed HE*ART on a screen, asked participants to stare at dot When asked what word they saw, participants generally replied with ART When asked to identify the word with their left finger, participants pointed at HE Case study: WJ (split-brain patient)
Evaluation (findings) Strengths: Supports concept of lateralization in the brain Provides details regarding the lateralized nature of each hemisphere Left hemisphere is the interpreter, while right hemisphere deals with perceptual grouping Weaknesses: Not necessarily applicable to all humans, as experimentation was done on split-brain patients Split-brain is not a naturally occurring affliction America-centered; cultural biases are not taken into consideration (eg. For language processing in Chinese speakers)
Methodology Strengths: Experimented on a large population of split-brain patients Tested both sides of the brain; did not assume control between the hemispheres Limitations: Used case studies (WJ) that arent necessarily applicable to everyone Extraneous variables not considered (culture, gender, handedness)
Works Cited Myers, D. G. (2007). Psychology . New York, NY: Worth Publishers. http://www.abc.net.au/rn/allinthemind/stories/2008/2276587.htm http://www.downstreamer.com/mindspast.html http://www.psywww.com/intropsych/ch02_human_nervous_system/dual_consciousness_in_split-brain.html

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Michael Gazzaniga

  • 1. Michael Gazzaniga Helena Yeung and Brian Zhao
  • 2. Background Born on December 12, 1939 Graduated from Dartmouth College in 1961, received his Ph.D at Cal Tech in 1964 Worked under Sperry as a his prot辿g辿 Sperry was a pioneer of human split-brain research Theories regarding functional lateralism in the brain had already been established
  • 3. Findings (split hemispheres) 1967 Experiment on split-brain patients Concluded that split-brain patients possessed two hemispheres that acted independently
  • 4. Findings (nonverbal right hemisphere) 1967 Experiment in split-brain patients Flashed a picture of spoon to participants right hemisphere Asked participant to identify the object: participants generally replied with I dont know. Asked participant to choose the object from a pile of objects: participants would generally choose correctly. Concluded that the right hemisphere in split-brain patients was nonverbal
  • 5. Findings (isolated hemispheres) Case study: WJ (epileptic patient with split-brain) Held apple to WJs right eye, and WJ would say, I see an apple Held apple to WJs left eye, and WJ would say, I dont see anything, but would be able to pick out a pictorial representation w/ left hand Concluded that two hemispheres of the split brain do not communicate with each other
  • 6. Findings (the interpreter) Gazzaniga labeled the left hemisphere as the brains interpreter (1998) Researchers noticed that, when information is sent to the right-hemisphere to control the left hand, the left hemisphere, when it sees this, interprets this event, and consolidates it with its ongoing mental monologue Gazzaniga proposed that the left hemisphere rationalizes the actions, protecting the holistic nature of the individuals mind, giving the individual a sense of self
  • 7. Findings (the gist capacity) Experiment: participants were asked to bet on which of two events would occur, one having an 80% chance of occurring, and the other having a 20% chance of occurring. Instead of choosing the event that repeatedly occurred, humans often attempted to discern patterns within the frequency of the events A rat would lose less money than a human through the same process, as they rely more on the right hemisphere Concluded that right brain takes events and images at face value, while the left brain made theories.
  • 8. Findings (right hemisphere) Perceptual grouping: You know that a specific object is at the bottom of a pile, and you go directly for it, without searching You see a deer in the woods; you can only see parts of the deer, but your brain mentally puts the missing pieces together
  • 9. Methodology Experiments: Performed on patients who had undergone split-brain procedures Studied with an apparatus that took advantage of separate visual fields If a split-brain patient is seated in front of a screen and told to look at an X in the middle of the screen, and if the picture is flashed on the screen too quickly for an eye movement to occur, then everything to the left of the X will go to the right hemisphere. Everything to the right of the X will go to the left hemisphere Displayed HE*ART on a screen, asked participants to stare at dot When asked what word they saw, participants generally replied with ART When asked to identify the word with their left finger, participants pointed at HE Case study: WJ (split-brain patient)
  • 10. Evaluation (findings) Strengths: Supports concept of lateralization in the brain Provides details regarding the lateralized nature of each hemisphere Left hemisphere is the interpreter, while right hemisphere deals with perceptual grouping Weaknesses: Not necessarily applicable to all humans, as experimentation was done on split-brain patients Split-brain is not a naturally occurring affliction America-centered; cultural biases are not taken into consideration (eg. For language processing in Chinese speakers)
  • 11. Methodology Strengths: Experimented on a large population of split-brain patients Tested both sides of the brain; did not assume control between the hemispheres Limitations: Used case studies (WJ) that arent necessarily applicable to everyone Extraneous variables not considered (culture, gender, handedness)
  • 12. Works Cited Myers, D. G. (2007). Psychology . New York, NY: Worth Publishers. http://www.abc.net.au/rn/allinthemind/stories/2008/2276587.htm http://www.downstreamer.com/mindspast.html http://www.psywww.com/intropsych/ch02_human_nervous_system/dual_consciousness_in_split-brain.html
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