split brain research Flashcards
corpus callosum
The two hemispheres are connected by the corpus callosum, which allows information received from one hemisphere to be sent to the other hemisphere.
Sperry - participants
His participants were a group of individuals who had undergone a commissurotomy - an operation where the corpus callosum is cut down the middle in order to prevent seizures.
When this main communication line between the two hemispheres was removed, Sperry could investigate the extent to which the two hemispheres were specialised for certain functions and if the 2 hemispheres performed tasks independently of each other.
Sperry - procedure
An image or word was projected to just a patient’s right visual field, so it was processed by the left hemisphere.
This could be repeated with an image or word projected to the left visual field so it was processed by the right hemisphere
Sperry - findings (describe what you see)
If the stimulus word was exposed to the right visual field, then it would be processed by the left hemisphere and the patient would say the word. This is because the left hemisphere contains the ‘language centres’ of the brain and so allows for speech. However, if the same stimulus word was exposed to the left visual field, then it would be processed by the right hemisphere and the patient would write the word using their left hand.
This is because the right hemisphere contains the visuo-spatial centres of the brain, allowing for the physical act of writing. The patient would not be able to give a verbal description of the word, because the right hemisphere contains no language centres.
Sperry - findings (drawing task)
Participants were presented with a picture/word in either their left or right visual field and they had to draw what they saw.
When presented to the right visual field (so processed by the left hemisphere) the participant would have to speak the word out loud to communicate it to the right hemisphere and they could then draw it.
However, when presented to the left visual field (so processed by the right hemisphere) participants used their left hand and were able to draw clearer and better pictures than with their right hand. Shows that the right hemisphere is dominant for visual motor tasks.
Sperry - conclusions
Certain functions are lateralised in the brain (i.e. language in the left hemisphere).
Connectivity between the different regions is important for the full operation of the brain.
AO3 - strength (Sperry)
Sperry’s experiments demonstrate that brain functions are lateralised. For example, if images processed in the right hemisphere can’t be spoken of, this suggests that the image processing and language processing do indeed happen in different hemispheres.
AO3 - limitation (Sperry)
Overly simplified: Sperry’s research often leads to the exaggeration and oversimplification of the different functions of the left and right hemispheres.
In reality, functions associated with one hemisphere (e.g. the left) can be carried out or shared by the other hemisphere when necessary.
AO3 - strength
A researcher found that split brain participants actually perform better than connected controls on certain tasks. For example, they were faster at identifying the odd one out in an array of similar objects than normal controls. This supports Sperry’s findings that the left and right hemisphere are distinct.
AO3 - limitation
The split-brain procedure is rarely carried out these days.
Therefore patients who have had this procedure are rarely encountered in sufficient numbers to be useful for research.
Many studies have only three participants, conclusions have often been drawn from individuals who have a confounding physical disorder that made the procedure necessary.
Therefore, findings cannot be generalised - low ecological validity.
& low in reliability as it is difficult to measure consistency of split brain research as it is rarely repeated.
