OCR AS Psychology: Core Studies - Sperry (2)

Aim/M&P:The aim of this experiment was to investigate the effects of hemisphere deconnection and to show that each hemisphere has different functions. The study is an example of a Quasi-experiment. The participants were 11 ‘split-brain’ patients, that is, they were patients who had undergone disconnection of the cerebral hemispheres. They were compared with performance of people who had no hemisphere deconnection. The participants had all undergone hemisphere deconnection because they had a history of advanced epilepsy which could not be controlled by medication. Sperry used a number of ingenious tasks in order to investigate lateralisation of brain function conducted in lab conditions, using specialised equipment which were highly standardised. One of the tasks used to send information to just one hemisphere involved asking participants to respond to visual information. This involved blindfolding one of the participant’s eyes and then asking them to fixate with the seeing eye on a point in the middle of a screen. The researchers would then project a stimulus on either the left or right hand side of the fixation point for less than 1/10 of a second. The presentation time is so small to ensure that the participant does not have time for eye movement as this would ‘spread’ the information across both sides of the visual field and therefore across both sides of the brain. As language is processed in the left hemisphere, when a stimulus is presented to the left visual field of a split-brain patient they should not be able to name the stimulus (as the image will be processed by the right hemisphere of the brain). Another of the tasks used to send information to just one hemisphere involved asking patients to respond to tactile information. This involved presenting a stimulus to one of the hands of a split-brain patient so the participant could not see the stimulus and then asking the participant to name it. If the stimulus is presented to the participant’s left hand the participant should not be able to name it.