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  • Sperry
    • Theory
      • The brain hemispheres mirror each other, but each have a functional localisation
      • The primary motor cortex is situated in the frontal lobe. Right hemisphere receives information from the activities of the left side of the body and vice versa
      • Split-brains reveal the ‘true’ nature of the two hemispheres because they can only work independently
    • Background
      • Previous research showed numerous behavioural effects, but they were much less severe than other cerebral surgeries
      • Sperry set out to show that each hemisphere possesses an independent stream of conscious-ness and has its own chain of memories that are inaccessible to the other
    • Research Method
      • Quasi/natural experiment because the IV wasn't directly manipulated
      • Ps' with split-brains had hemisphere deconnection. No controls were necessary because the visual fields/ hemispheres in non split-brain individuals was already known
      • IV: having a split brain or not
      • DV: ability to perform visual/tactile tests
      • Can be considered a collection of case studies
    • Sample
      • 11 patients who had their corpus collosum commis-surated to control severe epliepsy
      • 2 patients had surgery over 4/5 years before the study was conducted
      • 9 patients had surgery not long before the study
    • Procedure
      • Ps' had one eye covered, and stared a fixed point in the centre of the tachistoscopeVisual stimuli were back-projected at 1/ 10 of a second or less – too fast for eye movements to get the information into the wrong visual field. Everything projected to the left of the screen is given to the LVF/right hemisphere and vice versa
      • Objects were placed where ps' could not see, into their right/left hand or both. Information about objects in the left hand is processed by the right hemisphere and vice versa
      • Participants did visual and tactile tests
    • Results
      • Information shown to one VF could only be recognised if shown to the same VF
      • Information presented to the RVF can be described in speech/ writing with the right hand. If the same info is presented to the LVF, the ps insist they did not see anything/there was only a flash of light on the left side, it could not be described. However ps' could point with their left hand to a matching picture/object
      • If different figures were presented simultaneous-ly to different VFs eg. $ to the LVF and ? to the RVF, the ps could draw the $ sign with their left hand but reported that they had seen a ? 
      • Objects in the right hand could be described in speech/ writing with the right hand. If the same objects were placed in the left hand, ps' could only guess/were unaware they were holding anything 
      • Objects felt by one hand were only recognised again by the same hand
      • If objects were placed simultaneous-ly in each hand and then hidden, hands only selected their own object
    • Conclusions
      • People with split brains have two separate visual inner worlds
      • Split-brain patients second hemisphere does not know what the first hemisphere has been doing
      • Split-brain patients seem to have two independent streams of conscious-ness


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