Sperry (biological psychology)

• Date of study?

  1968
• Aim of the study?

  • to investigate the function of hemispheres and lateralisation of functions
  • does iIt happen in one hemisphere or both?
• Participants?


  • split-brain patients
  • 11 patients - male and female
  • all had undergone an operation called a commissurotomy
  • All had severe epilepsy prior to operation
• What is a commissurotomy?


  • severing of the corpus collosum
• Type of method?

  • lab experiment (had variables)
  • repeated measures (designs or left and right hemisphere)
• Independent variable?


  • information presented to right or right left hemisphere - can be manipulated as their corpus collosum is cut
• Dependent variable?


  • how they respond
• Control variable?


  • a controlled group of non-commissurotomised epileptics who would have had provided a better comparison
• What was the procedure?

  • Sperry presented information through using a tachistoscopic stimulus
  • To present it to a visual field, they covered one eye and presented the stimulus for 1/10 of a second. (seen through one visual field so only goes to one hemisphere)
• Task 1?

  • visual material presented to left or right hemisphere
  • material presented to right visual field goes the the left hemisphere (vice versa)
• What does left hemisphere do?

  • controls language
• What does the right hemisphere do?


  • controls recognition, emotions and spatial awareness
• Task 2?


  • touching something with right hand = able to identify
  • left hand = not able to identify
• Task 3?


  • simultaneously presented objects to each hand - put objects pack, relocate objects
  • if object was held with left hand, information sent from right hemisphere
  • left hand relocated and identified object
  • right hemisphere can recognise the object but not name it
• Task 4?


  • dollar was presented to left visual field
  • question mark presented to right visual field - shown at same time for 1/10 of a second
  • left hand to draw what they saw (drew dollar)
  • they said they drew the question mark - as left hemisphere has language and saw the question mark not dollar sign
• Task 5?


  • block design task:
  • did it with their right hand then their left hand
  • people were faster when they did it with their left hand - right hemisphere (recognition and spatial awareness)
• Task 6?

  • Nude lady task:
  • picture of nude lady was presented to left visual field for 1/10 of a second
  • participants had a reaction
  • when asked what they saw they don’t know (went to right hemisphere = no language)
  • shown to right visual field they had no emotion or reaction, but knew hat they saw (left hemisphere)
• Conclusions?

  • patients had split brain, so had independently working hemispheres
  • sperry could show that there was lateralisation of functions
  • left hemisphere = language, comprehension, writing
  • right hemisphere = recognition, emotions, spatial awareness (aphasic - no language)
• Data collection?

  • qualitative and quantitative data
• Ethics?


  • had the right to withdraw
  • no deception
• Validity?


  • lacks ecological validity
  • has high internal validity (aim was met)
  • took place in highly controlled environment-possible to eliminate many extraneous variables
• Determinism?


  • can’t control what the brain does
• Reliability?


  • lacks inter-rater reliability as there was only one observer for all participants
  • replicable
  • types of damage to the hemisphere is unrepresentative so the findings may be less generalisable
• Ethnocentrism?


  • the results are generalisable for any ethnic group as the neocortex evolves in all humans, despite only white people having access to the surgery
• Psychology as a science?


  • has a hypothesis and an aim
• Usefulness?

  • has replicability
  • supports aim