Lateralisation + Split-brain research Flashcards
define lateralisation
the idea that the hemispheres of the brain are functionally different and that certian mental processes and behaviours are mainly controlled by one hemisphere rather than the other.
As in the example of language which is localised as well as lateralised
define hemispheric dominance
the preference for using one side of the brain
what is meant by split-brain research
Split-brain research is a series of studies (which began in the 1960’s and are still ongoing) involving people with epilepsy who had experienced a surgical seperation of the hemispheres of their brain to reduce the severity of their epilepsy. This enables researchers to test lateral functions of the brain in isolation.
Who is the key peice of research for split-brain research
Sperry 1968
What was the procedure of Sperry 1968
Method 1: visual: An image was projected to a participants RVF and the same or different image was projected to the LVF. When two different images were presented simultaneously on either side of the visual field. The participant is then required to draw with their left hand (which was shielded from view) what they had seen.
method 2: touch: Objects were given to the participants to identify by touch. 2 different items were placed in the participants hands at the same time and then they were removed and hidden in a ‘grab bag’ or scrambled amoung other test items. Each hand hunted through the pile and searched out its own object.
Give the results of Sperry 1968
method 1: visual: The participant was then require to say the object they had drawn. The participant would name the object from the RVF despite having drawn a different object that had been present in their LVF.
method 2: touch: Although the performance of a ‘normal’ participant would be slowed down by the competing demands of the tasks, the people without the connected corpus callosum could perform these double tasks in paralel as quickly as though performing them individually.
What is Sperry 1968 conclusion
These observations show how certain functions are lateralised in the brain and support the view that the LH is verbal and the RH is ‘silent’ but emotional.
Evaluate Sperry 1968
W - distress - the patients didn’t know why they drew what they did.
W - small sample size - difficulty generalising to non-split-brain patients.
W - sample - some had the corpus callosum cut completely
W - Sperry’s control group were neurotypical, non had epilepsy
Evaluate Split-brain research
W - epileptic patients are often prescribed medication. This may influence theur behaviour and cognitive abilities more than the split-brain surgery.
W - different patients experience different amounts of corpus callosum severing and so their results should not be compared.
Evaluate - lateralisation
S- supported by scientific research - Sperry
W- research is on small samples with unusaul brain structure, so results are difficult to generalise to typical individuals
W - Lateralisation is oversimplified view of brain function.
