split brain research

• Hemispheric lateralisation


  Two halves of the brain are functionally different, each hemisphere has functional specialities (e.g. left = language, right = visual motor tasks)
• Corpus Callosum


  The two hemispheres communicate as they are connected by the Corpus Callosum, a thick bundle of 200-300 million nerve fibres.
• What is done to split the brain?

  Cutting the corpus collosum which was a surgical procedure for epilepsy. Isolating each hemisphere from the other. The corpus callostomy reduces epileptic symptoms and has few side effects for such an invasive procedure. However, unusual behaviour and a sense of a loss of agency led to research.
• Sperrys split brain research - Procedure


  Quasi-experiment using 11 participants who all undergone corpus callosotomy.

  Sperry projected information to each visual field, so controlling the information that each hemisphere has access to.

  In a series of tests, participants would be required to either say what they had seen, draw the object or select from a number of objects that were hidden from view with their hands.
• Sperrys split brain research - Findings

  Information presented to the left hemisphere could be spoken, but not spoken if delivered to the right hemisphere.

  However, the right hemisphere could draw or select the object by using the left hand.

  Suggesting the hemispheres are both capable of acting independently (memories and awareness) also supporting the theory that language centres are in the left side of the brain.
• Gazzanigas split brain research


  Used patients who had undergone corpus collosotomy.

  Found that when each hemisphere or split-brain patients were presented with faces the right hemisphere was much more able to recognise them.

  Suggesting that the right hemisphere is specialised for facial recognition.
• / Small sample size in Sperry's research


  E - In Sperry's research, they only 11 participants who were all epileptic.

  E - Since they were all epileptic, their brains may have been affected by seizures.

  L - Therefore, this makes it hard to generalise to people who do not have epilepsy due to participant variables.
• / Research lacks mundane realism


  E - The experimental procedure used in split brain research is unlike how these individuals would process information and act in normal day to day life.

  E - The findings from the research may not generalise to anything which occurs outside the study.

  L - Therefore, the research lacks mundane realism.
• + Close control in Sperry's research


  E - Patients were given eye patches, and images were flashed up for a very brief time, meaning there was no possibility of looking over and using the other visual field.

  E - This strengthens internal validity of the research as there is no confounding variables.

  L - However, no control group of non-epileptics was used which means findings cannot be compared.