Lateralisation of function

• What is lateralisation?

  • two hemispheres
  • Each responsible for its own specific functions
  • Not localised
• What Does the corpus callosum do?

  It’s a bundle of nerve fibres and is the connection between the two hemispheres
• The Right Hemisphere:

  • ‘the synthesiser‘
  • Creative
  • Spatial awareness, recognition of objects and faces
• The Left Hemisphere:

  • ‘academic’
  • Language, mathematical skills, recognition of names and words / letters / numbers
• What ppts did sperry use?


  brain research on 11 epileptic patients who had their brains split through surgical lesioning (severing of the corpus callosum)
• What did Sperry do?

  • ppts had one eye covered + had to fix their vision on a dot in the centre of the screen
  • Words flashed briefly on either the right side or the left side
  • Then asked what they saw
  • Words that flashed on the right field of view entered the left hemisphere and vice versa
• What were Sperry’s findings?

  • words presented on the left visual field = could draw but not name
  • Words presented on the right visual field = could describe or name it
  • Conclusion = functions are lateralised
• Strength: developed understanding of lateralisation

  • pivotal in establishing the differences in functions between the two hemispheres
  • Left hemisphere was demonstrated as being dominant for language tasks (containing language centres)
  • Right hemisphere was demonstrated as being dominant for visuo-spatial tasks
  • So the research suggests the left hemisphere is the analyser and the right is the synthesiser.
  • Therefore - research has made strong contributions to our understanding of the differences between hemispheres + their functioning
• Strength - standardised procedure

  • standardisation of presenting visual info to one hemisphere at a time was well controlled
  • Allowed the basic procedure to be varied very easily (4 conditions / ensuring only one hemisphere was receiving info)
  • Therefore this research has high internal validity and therefore has high credibility
• Strength - Roger’s et al

  • domestic chicken - brain lateralisation is associated with an enhanced ability to perform two tasks simultaneously
  • finding food and being vigilant for predators
  • Using only one hemisphere to engage in a task leaves the other hemisphere free to engage in other functions
  • Therefore - this demonstrates how lateralisation can enhance brain efficiency in cognitive tasks.
• Weakness - Rogers et al

  • Animal research
  • impossible generalise to humans.
  • If we can only experiment on animals like chickens or rats, it may not be accurate as we have higher order thinking and brain anatomy is different in size
  • Therefore- human brains could be different in structure and function too
• Weakness - small sample size

  • low population validity, so low external validity
  • only 11 ppts, all who had epilepsy
  • the disorder itself may have caused changes in the brain that influenced the findings.
  • Therefore - Sperry’s research lacks credibility and his findings are incredibly difficult to generalise
  • also- low ecological validity = flashing images with one eye covered unlikely to happen in real life