Sperry research Flashcards
aim
to study the psychological effects of hemispheric disconnection in split-brain patients and understand how the hemispheres function in ‘normal’ individuals
sample
- 11 participants
- All had severe epilepsy
- They couldn’t be treated with drugs / meds
- They had their corpus collosum severed (split) as a result to attempt to cure / treat this condition
- 9 had been operated on to recently to do a therapeutic evaluation - this would have told us if there was any injury or damage done to the brain. 2 of these patients were still experiencing seizures
- 1 patients had been operated on 5 and 1/2 years prior and showed no signs of epilepsy or injury
1 patient was a mother and housewife in her 30s who had been operated on 4 years before and was also seizure free
procedure - visual tasks
Sperry carried out a number of visual and tactile tasks with the participants. Each participant was tested individually and not as a group.
Visual tasks - - Participant will gaze (with one eye covered) at a fixation point on a translucent screen. - A tachistoscope is used with 35mm slides arranged in a standard projector - images on the slides were projected either left or right of the fixation point for 1/10th of a second - either in the left or right visual field
why’s it only flashed for 1/10th of a second? - visual task
this is so that the fixation point doesn’t move and therefore the visual field isn’t changed
procedure - tactile tasks
there is a gap underneath the screen the participant would reach the objects but they could not see them or their hand.
objects were placed in participants left / right hands (or both)
info in the left hand is processed by the right hemisphere and vice versa
research method
both a quasi experiment and a case study
has a naturally occurring IV
IV
whether or not the participant had a served corpus collosum or not, although all participants had a severed corpus collosum sperry already had a ‘normal’ control group of ‘neurologically typical individuals’
DV
ability to perform tactile and visual tasks measured through a controlled observation
case study
case studies are. small group of people in depth, usually conducting multiple measures over time (longitudinal)
sperry’s participants were in detail and were all participating in multiple tasks
results from visual task
when an object is displayed in the right visual field the participant is able to describe the object in speech and writing.
when the object is placed in the left visual field, participants insist that they have not seen it but asked to used the LEFT HAND to point to a matching object on the table. they do this while they insist nothing was seen
the left VS is controlled but the right hemisphere, left hemisphere is in control of language and the two hemispheres are disconnected so they can’t physically tell you as it requires the use of language which would require communication with each side of the brain which is not possible when the corpus collosum is severed
results from tactile task
when the object was in the right hand participants were able to explain the object through speech and writing
when object in left hand participant could guess what they were feeling as they couldn’t name the object in speech and writing but they could correctly pick the object out of a range of objects when using the LEFT HAND
when objects were placed in each hand then hidden for retrieval in pile of items, each hand searched for its own object but if the lefthand picks up the object that the right hands searching for it gets rejected. the other hand will then continue to search.
if the lefthand when searching couldn’t find the previous object it would find something similar showing that the right hemisphere is capable pf sorting things into categories.
this sums up to the idea that the two hemispheres are not equal with respect to intellectual functioning
right hemisphere has some reasoning ability
conclusion
people with split brains have two separate visual inner worlds, each with its own train of visual images. - this means that each only attends to the visual field it is assigned to and not both VS’. however in real life both eyes focus on the same thing
split brain patients have a lack of cross-integration where the second hemisphere does not know what the first hemisphere is doing - when the participant is asked to say what object that they have been shown / felt with the RVF or right hand they either incorrectly guess, say they don’t know or say there was nothing
split brain patients seem to have two independent streams of consciousness, each with its own memories, perceptions and impulses. - basically 2 minds one body
right has no idea what left is doing as it is unable to communicate via language with the other hemisphere.
