split-brain research

• functions of the two hemispheres

  lateralisation - the idea that the two halves of the brain are functionally different and some mental processes are mainly controlled by one hemisphere

  • left hemisphere - language, computation and logical reasoning
  • right hemisphere - spatial reasoning, facial recognition and music
• split-brain research - studies looking at epileptic patients who have experienced surgical separation of the two hemispheres of the brain
• split-brain research


  sperry - studied split-brain patients who had an operation that severed the corpus collosum, which allows us to see how the hemispheres are specialised for different functions as they are unable to communicate with eachother

  • 11 split-brain patients
  • patient given a 'fixation point' to look at on a screen
  • image is presented to the left or right visual field
  • the function of each hemisphere is viewed in isolation as information can't be transferred from one to another

  
• findings - describing what you see

  • when a picture of an object was shown to the right visual field they could easily describe what was seen as language and right visual field information are processed in the left hemisphere
  • when it was shown to the left visual field they couldn't describe it or typically said there wasn't anything there because left visual field information is processed in the right hemisphere which has no language centre
• findings - recognition by touch

  • individuals were able to find an object from a bag without seeing them if they were presented with a word in their left visual field and using their left hand as they are both controlled by the right hemisphere which specialises in spatial awareness
  • they couldn't use their right hand to find an object when presented the word in their right visual field because the left hemisphere isn't specialised for spatial skills
• findings - composite words

  if two words were presented simultaneously (one to each visual field) the individual would select the object presented to their left visual field using their left hand because the right hemisphere controls spatial tasks, but they would say the word in their right visual field as the left hemisphere controls language production
• findings - matching faces

  • when matching a face from a series of other faces the picture the picture processed by the left visual field was selected while the picture presented to the right was ignored
  • when each visual field was given a half of different faces, the face in the right visual field would be described but the individual would pick a picture that matched the face in the left visual field
• evaluation - research conclusions

  sperry's research showed that the brain has lateralised functions

  • other research shows that the right hemisphere can produce basic words and phrases and contributes to emotional and holistic content in language
• evaluation

  + highly standardised and specialised procedures

  + well controlled

  + led to theoretical and philosophical debates

  - differences in function of the hemispheres is exaggerated eg. some language functions such as tone recognition are in the right hemisphere

  - may be issues in generalisation as all participants had severe epilepsy

  - control group used had no history of epilepsy which may be the third variable