A03 Split-Brain Research Into Hemispheric Lateralisation

• Demonstrated lateralised brain functions

  Sperry and later Gazzaniga's work into split brain phenomena has produced an impressive and sizeable body of research findings.
• The main conclusion of Sperry and Gazzaniga's work (Demonstrated lateralised brain functions )

  Left hemisphere is more geared towards analytic and verbal tasks and the right is more adept at performing spatial tasks and music. The right hemisphere can only produce rudimentary words and phrases but contributes emotional and holistic content to language. Thus, the left hemisphere is the analyser and the right hemisphere is the synthesiser.
• Strengths of methodology


  Highly specialised and standardised procedures used. Sperry's method of presenting visual information to one hemisphere at at time was ingenuous.
• Presenting to one hemisphere at a time (Strengths of methodology)

  As the ppts were told to look at a fixed point, an image would be flashed up for 1/10 of a second meaning the ppts would not have time to move their eye across the image and so spread into across both sides of the visual field and therefore, both sides of the brain.
• Consequences of presenting to one hemisphere at a time (Strengths of methodology)

  This allowed Sperry to vary aspects of the basic general procedure and ensure only one hemisphere was receiving information at a time. Thus, developing a very useful and controlled procedure.
• Theoretical basis


  Sperry's work prompted a theroretical and philosophical debate about the degree of communication between the two hemispheres in everyday functioning.
• Pucetti et al (Theoretical basis)


  Suggested that the two hemispheres are so functionally different that they represent a form of duality in the brain - we are all two minds. Other psychologists argue that the hemispheres are far from working in isolation and are a highly integrated system and are both involved in most every day tasks
• Issues with generalisation


  Many researchers have urged caution in the widespread acceptance of this theory as split-brain patients constitutes an unusual sample of people. Only 11 ppts took part in all variations of the procedure and they all had evidence for past epileptic seizures.
• Consequence of epileptic seizures (Issues with generalisation)

  Argued to have caused unique changes in the brain that may have influenced the findings. Also, some ppts expereinced more disconnection to the two hemispheres as part of their surgical procedure. Thus, the control group of 11 by Sperry with no past epileptic history may have been inappropriate.
• Differences in function may be overstated


  One legacy of Sperry's work is a growing body of pop-psychological literature that overemphasises and oversimplifies the functional distinction between the left and the right hemispheres. Modern neuroscientists would contend that the actual distinction is less clear cut and much more messy than this.
• The two hemispheres in a 'normal brain' (Differences in function may be overstated)

  In the normal brain the two hemispheres are in constant communication when performing every day tasks, and many of the behaviours typically associated with one hemisphere can be effectively performed by the other when the situation requires it