Split-brain Research

Split brain operation

A surgical procedure used to reduce epilepsy. When the corpus callosum is severed (cut in two halves) and aims to stop erratic electric messages travelling between hemispheres

Sperry’s aim (1968)

Examine the extent to which the two hemispheres are specialised for certain functions

Sperry’s procedure

Studied 11 people who had a split brain operation. Was based on the brain being contralateral - info from the left visual field goes to the RH. Projected info into each visual field

Describe what you see

An image was shown to the right visual field, could describe what was seen, processed by the left hemisphere. When shown to the left visual field, couldn’t describe with words. Info went to the right hemisphere. Said that there was nothing there

Tactile task (touch)

Series of objects were placed into their hands. When placed in the right hand, could describe it using speech or writing. When placed in the left, made guesses of what it was

Drawing task

Asked to draw a picture shown to the right visual field (LH), the right hand did worse than the left (RH). Asked to draw a picture shown to the left visual filed (RH), the left hand drawings were better. All participants were right-handed

Sperry’s conclusion

Observations show how certain functions are lateralised in the brain. Supports the view that left hemisphere is dominant in visual speech and language, right is dominant for visual-motor tasks

A strength of split-brain

Support from more recent research. Gazzinga showed that split-brain patients performed better on certain tasks. Supports Sperry’s findings that the left brain and right brain are distinct

A limitation of Sperry’s research

Doesn’t have valid comparison groups. The behaviour of Sperry’s group was compared to a neurological control group, none of the participants had epilepsy. A confounding variable, differences observed between the groups may be the result of epilepsy

Furthermore point of the limitation

There are issues with making generalisations from his findings. Research relates to a small sample, there were individual differences. Issues with external validity and generalising beyond the participants