Split Brain Research

• what is the corpus callosum?

  - a thick bundle of 200-300 million nerve fibres that connects the left and right hemispheres
• what happens if the corpus callosum is severed?

  - cutting the corpus callosum is a surgical procedure for epilepsy, isolating each hemisphere from the other

  - the corpus callosotomy reduces epileptic symptoms and has a few side effects for such an invasive procedure

  - however, unusual behaviour and a sense of a loss of agency (feeling of control)
• how was the Sperry (1968) study carried out?

  - 11 patients had undergone corpus callosotomy

  - projected info to each visual field, Sperry controlled the info that each hemisphere has access to

  - in a series of tests, ppts would be required to either say what they had seen, draw the object or select from objects that were hidden from view with their hands
• what did the Sperry (1968) research find?

  - info presented to the LH could be spoken but not spoken if delivered to RH

  - however, the RH could draw or select the object by using the left hand

  - suggesting the hemispheres are both capable of acting independently (memories and awareness)
• what did Gazzaniga's (1983) study find?

  - found that when each hemisphere of split-brain patients was presented with faces, the RH was much more able to recognise them

  - suggesting that the RH is specialised for facial recognition
• what wider effect has the research on split-brain patients had?

  - a fundamental impact on the psychological and philosophical understanding of both the unity of consciousness and identity

  - suggesting that the brain is a combination of separate intelligent processes working together
• what is the problem with the samples used in split-brain research?

  - the sample of split-brain patients in these studies is small; ppts were compared against non-epileptics, had varying amounts of connection cut, and all undergone drug therapy

  - this suggests some of the result may have been due to ppt variables meaning the results are not generalisable to the wider population
• how can split-brain research be argued to lack validity?

  - the experimental procedure used in split-brain patients is unlike how these individuals would process info and act day-to-day (lacks mundane realism)

  - low external validity: in real life, both LH and RH would have access to info by moving the head