Lesson 8 - Split-brain research Flashcards
Sperry and Gazzaniga (1967) - Method
- They were the first researchers to study split brain research
- They used the divided field procedure, where an image or word is presented to the left visual field, which is processed by the right hemisphere and vice versa. In patients with a split brain, the two hemispheres will not communicate and this gives the opportunity to see which brain is more dominant in certain behaviours
Describe test - a picture was presented to either the left or right visual field and the participant had to describe what they saw
Tactile test - an object was placed in the patients left or right hand and they had to describe what they felt and select a similar object
Drawing test - participants were presented with a picture in either their left or right visual field and they had to draw what they saw
What is split brain research?
It is used to study lateralisation, and it involves the corpus callosum being cut in order to cease communication between the two hemispheres. This is a treatment for patients with severe epilepsy. It is known as commissurotomy
Sperry and Gazzaniga (1967) - Findings
Describe test - the picture presented to the right visual field (processed by left hemisphere), the patient could verbally describe what they saw, showing that the left hemisphere is dominant in language production. When it was presented to the left visual field (processed by the right hemisphere) it was often reported that there was nothing present and they could not describe what was shown
Tactile test - Objects placed in the right hand (processed by the left hemisphere) resulted in the patients describing verbally what they felt and being able to select a similar object from a series of alternate objects. When the object was placed in the left hand (processed by the right hemisphere) the patients could only make wild guesses as to what it was, but they were able to select a similar object to the test object
Drawing test - when a picture was presented to the right visual field (processed by the left hemisphere) the right hand would attempt to draw the image, but it was not as clear as the left hand, showing that the right hemisphere is dominant in visual motor skills. When the picture was presented in the left visual field (processed by the right hemisphere) and the left hand attempted to draw it, it came out consistently clearer despite all the patients being right handed. This demonstrates the superiority of the right hemisphere in visual motor tasks
Therefore, The left hemisphere is dominant in language production, whereas the right is dominant in visual motor tasks
Turk et al (2002)
He was interested in facial recognition post-commissurotomy
- He studied a patient called JW who had the surgery 23 years earlier and had been extensively studied
- He was presented with a stimuli: a morphed face, containing differing proportions of his own face, and a familiar researcher’s face who he had worked with many times. The combination was from 0% JW/100% researchers to 50/50 to 100% JW/0% researchers
Turk used the divided field procedure, and JW was asked to press a button if the image presented in either visual field was his own or the researchers
Results found that the right hemisphere had a clear bias towards recognising the morphed face as the familiar other and the left had a clear bias towards recognising it as himself
Therefore the left was more important in self-recognition and the right is better at facial processing
Strengths of split brain research
- We can prove that there is hemispheric lateralisation as shown is Turk’s and Sperry and Gazzaniga’s research
Weaknesses of split brain research
It is difficult to generalise these findings, because there are very few patients who have split brains and few of them have been studied, plus, they are not always comparable because some patients did not have the corpus callosum fully cut, allowing for some communication
It also lacks temporal validity, as we do not need to carry out commissurotomy in order to study the brain as technology has advanced enough, so it is not relevant today
