Background/context
Localisation - a limitation of a brain function to a particular structure
Lateralisation - limits a function to 1 hemisphere
Physiological approach could explain difficulties experienced by individuals with a split brain
The 2 hemispheres of the brain work independently and don't transfer info from side to side
No important behavioural aspects of surgical of surgical commiseratory
Movement/activity on each side is controlled by opposite sides of the brain = contralateral control
Aim
To test the effects of the hemispheric de-connection in humans, to see if cognition differs between hemispheres
Method
Quasi experiment because the IV (split brain or not) is natural
P's with split brains had undergone commiseratories to reduce severe epilepsy
No control group necessary
DV= P's ability to perform visual and tactile tests
Qual. data gathered through self reports
Procedure
1. Visual info-
P covered 1 eye and centered gaze on a fixed point on a screen
Visual stimuli were projected for 1/10 of a second or less, too fast for eye movement.
Everything was projected to the left side of the screen was passed via the left visual field to the right hemisphere and vice versa
2. Tactile info-
Below the screen was a gap so that the p's could touch but not see the objects
Objects were placed into p's hands and information about the objects when placed in the left hand was processed by the right hemisphere of the brain and vice versa
Findings
1. Visual-
Info shown to L.v.f. could be recognised only if shown to the same side of the screen
Info presented to the R.V.F could be described in speech and writing
When the same info presented to LVF, p didn't see anything or said there was only a flash, they could not describe or write it
If different symbols were shown at the same time to both fields, e.g. $ and ?, the p could draw the $ but could only report a ?
2. Tactile tests-
Things in R.H could be described in speech and writing but if some things were in the L.h, P's just made guesses
Things touched were only recognised by the right hand
Conclusions
Split brain patients have 2 separate minds and lack cross-integration, 2nd Hemisphere doesn't know what the 1st Hemisphere is doing
We have 2 streams of consciousness with our memories, perceptions and impluses
Evaluation
Research method- lab experiment with 2 conditions
Data type-detailed qual. data and quant. data
Ethics- ethical surgical issues, there are many ways split brain patients could be emotionally affected
Validity- high control so extraneous variables are limited, visual restrictions are imposed, the stimuli was only shown for a short time and there was a lack of realism
Reliability- easy to replicate the experiment
Sample- 11 men and women, but it was a restricted sample because they all used to suffer from severe epilepsy