Split-brain research into hemispheric lateralisation

• What is hemispheric lateralisation?

  The idea that the two halves of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other.
• Sperry's studies involved an unique group of individuals, all of whom had undergone the same procedure in which the corpus callosum which connects the two hemispheres was cut in order to separate the two hemispheres.
• Sperry devised a general procedure in which an image or word could be projected to an individual's right visual field and the same, or different, image could be projected to the left visual field. Presenting the image to one hemisphere of a split-brain individual meant that the information could not be conveyed from that hemisphere to the other.
• Recognition by touch:

  Although individuals could not attach verbal labels to objects projected in the left visual field, they were able to select a matching object from a grab-bag of different objects using their left hand.
• Composite words:

  If two words were presented simultaneously, one on either side of the visual field, the individual would select a key with their left hand and say the word 'ring'.
• Matching faces:

  The right hemisphere also appeared dominant in terms of recognising faces. When asked to match a face from a series of other faces, the picture processed by the right hemisphere (LVF) was consistently selected, whilst the picture presented to the left hemisphere was consistently ignored.
• AO3 - Demonstrated lateralised brain functions:

  Sperry's research had concluded that the left hemisphere is more geared towards analytic and verbal tasks whilst the right is more adept at performing spatial tasks and music. This is a key contribution to our understanding of brain processes.
• AO3 - Strengths of the methodology:

  The experiments involving split-brain individuals made use of highly specialised and standardised procedures. The image projected would be flashed up for one-tenth of a second, meaning the split-brain individuals would not have time to move their eye across the image and so spread the information across both sides of the visual field and the brain. Thus Sperry developed a well-controlled procedure.
• AO3 - Theoretical basis:


  Sperry's work prompted a theoretical and philosophical debate about the degree of communication between the two hemispheres in everyday functioning and the nature of consciousness. For example, some theorists have suggested that the two hemispheres are so functionally different that they represent a form of duality in the brain.
• AO3 - Issues with generalisation:


  Split-brain individuals constitute such an unusual sample of people. There were only 11 who took part in all variations of the basic procedure, all of whom had a history of epileptic seizures.