Sperry (Brain)
Sperry (1968) Hemisphere Deconnection (textbook pg. 90-94)
“Understand the aims, procedures and findings (results and conclusions), strengths and weaknesses of: Sperry (1968) Hemisphere Deconnection and Unity in Conscious Awareness.”
Background: To treat severe epilepsy, the corpus callosum can be cut to disconnect the left and right hemispheres of the brain (to stop seizures spreading from one hemisphere to the other). Without the corpus callosum, the two hemispheres seem to act independently, like two separate brains (split brain) instead of one whole brain.
Description: APRC
| A | • Sperry aimed to investigate the information processing of “split brain” participants, whose corpus callosum had been cut. • Sperry also aimed to investigate the functions of the left and right hemispheres. |
| P | • There were 11 participants with a cut corpus callosum, each given a series of tasks. • VISUAL TASKS: Participants focused on the midpoint of a screen. Information was presented to the left and right visual fields (left and right side of the screen) just for 1/10th of a second. • The participants were then asked to say what they had seen on the screen or point to a picture that matched what they had seen. • TACTILE TASKS: Other tasks included identifying objects from touch alone (no sight) and trying to name these objects or search for the them by feeling for them amongst piles of different objects. • All of the tasks required participants to process sensory information from one of the two hemispheres and then use the same or the opposite hemisphere to respond to the information. |
| R | • When words/images were shown to the RIGHT visual field (LEFT hemisphere) they could SAY the word back. But they couldn’t point to the image they had just seen. • When words/images were shown to the LEFT visual field (RIGHT hemisphere) they could POINT to the image. But they couldn’t say the word. • When objects were felt with the RIGHT hand (LEFT hemisphere) they could SAY the name. When objects were felt with the LEFT hand (RIGHT hemisphere) they couldn’t say the name. • When objects were felt by the RIGHT hand, they could only be found again using the RIGHT hand. When objects were felt by the LEFT hand, they could only be found again using the LEFT hand. This is because the two hemispheres can’t communicate. |
| C | • Sperry concluded that each hemisphere is capable of working independently to the other hemisphere. • Sperry also concluded that each hemisphere seems to have its own memories, which cannot be shared to the other hemisphere without the corpus callosum. • Sperry also concluded that the left hemisphere controls more language abilities and the right hemisphere controls more spatial abilities. |
Evaluation: GRAVE
| G | • The sample of 11 participants is very small, meaning the results may lack generalisability. |
| R | • Standardised procedure which can easily be replicated, to check for consistency of results over time. For example, all words/images were presented for 1/10th of a second. |
| A | • From Sperry’s research, he confirmed the functions of either hemisphere, adding to knowledge in Psychology. • He also identified the side-effects of cutting the corpus callosum, therefore …. |
| V | • There is low ecological and task validity – the laboratory setting and artificial tasks are nothing like information processing in everyday life. E.g. you never have to recall images you have only seen for 1/10th of a second or look at images with one eye then find the related object. |
| E | • There are no major ethical issues with the procedure. Participants would have given informed consent to participate in the research. |
Sperry (1968) Key Term Glossary
| Corpus callosum | A large bundle of nerve fibres that connects the two hemispheres so they can communicate. |
| Epilepsy | A disorder that affects the brain, that causes the patient to have epileptic seizures. |
| Split-brain | Term given to patients that have their corpus callosum cut, meaning the left and right hemispheres work independently, without communicating. |
| Left hemisphere | The half of the brain mostly responsible for processes such as language and speech recognition and production. It is also responsible for logical thinking. |
| Right hemisphere | The half of the brain mostly responsible for processes such as spatial awareness, musicality, creativity and face recognition. |
| Need more help? Want to stretch your understanding? Need a video example? |
| http://holah.co.uk/study/sperry/ http://psychyogi.org/sperry-1968-split-brain-study/ |
| https://www.youtube.com/watch?v=82tlVcq6E7A (10 min split brain case) https://www.youtube.com/watch?v=SaZcIVvLmeM (2 min summary of the experiment) |
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