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Sperry (Sample (11 patients who had undergone 'an extensive midline…
Sperry
Sample
11 patients who had undergone 'an extensive midline section of the cerebral commissures in an effort to control severe epileptic convulsions not controlled by medication' (hemisphere disconnection)
2 studied in detail:-The first patient (man) had his surgery over 5½ years before study. Second patient, housewife n mother in her 30's, had her surgery more than 4 years before the study.
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Findings: Visual tests
Info presented to the RVF could be described in speech and writing. If the same info is presented to the LVF the participant insisted he either didn't see anything or was a flash of light.
When composite words were flashed the letters are responded to separately. E.g 'keycaps' the LVF would read key and RVF read case. When responding, person would pick up a key with left hand but say case.
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Research method
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Been argued that because extensive tests were carried out on a very small sample, this study can be considered a collection of case studies.
Usually considered a quasi/natural experiment because the IV (having a split brain or not) was not directly manipulated by the researchers, already undergone the surgery. No control group was necessary because results for the non split brain was already known
Findings: Tactile tests
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Objects placed in the right hand(LH)could be described in speed or writing, same object in left hand they could only make wild guesses
Conclusions
People with split brains have two separate visual inner worlds, each with its own train of visual images
The corpus callousum is responsible for passing information between the hemispheres. Split brain patients have a lack of cross integration where the second hemisphere doesn't know what the first hemisphere has been doing.
Split brain patients seems to have two independent streams of consciousness, each with its own memories perceptions .
Procedure
Presenting tactile information:
-Gap under translucent screen so participants could reach under but not see hands. Objects were placed in either right/left hand or both hands. Info about objects placed in the left hand is processed by the right hemisphere and vice versa.
Procedure
Presenting visual information:
-Participant with one eye covered fixed eyes on a fixed point. Visual stimuli was projected for 1/10 of a second. Everything projected to the left of the central meridian of the screen is passed via the LVF to the right hemisphere and vice versa.
Aim
To show that each hemisphere:
-possesses an independent stream of conscious awareness
-has its own separate chain of memories that are inaccessible to the other
Procedure
Perry used a number of ingenious tasks in order to investigate the functions of the right and left hemisphere (lateralisation of brain function). Tasks were in lab conditions, using specialised equipment (tachistoscope) and were highly standardised.