Sperry Flashcards
Background
The brain is split into two hemispheres: each with different abilities.
Left: language, logic, analysis.
Right: spatial abilities, creativity, music.
They are attached by the corpus callosum (a collection of nerve fibres).
Epilepsy: brought on by abnormal electrical impulses discharging within the brain disrupting normal brain patterns.
In the 1940s, a treatment was developed called ‘split brain surgery’ in which the corpus callosum was cut so abnormal electrical impulses couldn’t spread throughout the brain.
Aims/ hypothesis
To study the functions of separated and independent hemispheres.
Visual fields: the left visual field is from the right hemisphere.
The right visual field is from the left hemisphere.
Research method.
Quasi experiment
IV- split brain or not
DV- ability on tasks
IV is naturally occurring and can’t be manipulated.
Sample
11 patients who had undergone split brain surgery/ commisurotomy.
These were compared against people who had not had the surgery.
Opportunity sampling.
Weakness of Sperry’s sample
small sample size
2 had the surgery 4/5 years ago so may have adapted since.
perhaps epilepsy was causing the result not the surgery.
Why Sperry used the sample that he did.
participants had two hemispheres separated so were able to test the function of each individually.
no other choice but to use opportunity sampling, can’t make people have the surgery.
What was the equipment used
Tachistoscope:
Projector
Fixation point in middle of the screen
Objects on table (can’t see them)
Hand shield
Controls
symbols displayed
images displayed
objects used
fixation point
1/10th of a second = time for presentation
hands out of view
one eye covered
tachistoscope
Procedure: objects presented in the right visual field.
What the participants could do
What this tells us about the relevant hemisphere.
Objects presented in the right visual field.
Information went to the left hemisphere.
Can describe it in speech and written format.
Left hemisphere can communicate anything from the right visual field or experiences of the right side of the body.
Procedure: objects presented in the left visual field.
What the participants could/ couldn’t do
What this tells us about the relevant hemisphere.
Information went to the right hemisphere .
If asked to point to a matching object on the table with their left hand they can. They can also draw it with their left hand.
Participants insist they haven’t seen anything so can’t describe it verbally.
Right hemisphere doesn’t have language ability. They can show non-verbally that mental processes from the left visual field and left side of the body are present.
Procedure: an image of an apple was presented to the left visual field and an image of a key to the right. These were presented simultaneously and the participant was asked to draw with his left hand (out of sight) what he’d seen.
What the participant could / couldn’t do.
Able to say they had seen a key (RVF) but unaware of anything else.
Able to draw apple (LVF) with left hand but not consciously know why. Able to name object once they had seen the drawing in the RVF.
Were not sure why they’d drawn an apple.
Procedure: simple mathematical problems presented to left visual field.
What the participant could / couldn’t do.
What does this tell us.
Info went to right hemisphere.
Were able to sort objects by shape, size, texture using left hand. Can solve simple arithmetic or addition by pointing to correct answer with left hand.
Right hemisphere can process mathematical/ special information.
Procedure:
A nude pin up presented to left visual field.
What the participant could / couldn’t do.
What does this tell us.
Info went to right hemisphere.
Participants would giggle/look embarrassed when nude pictures appeared.
Couldn’t say what they were giggling/ embarrassed about.
Non-verbal response suggested the right hemisphere has a second conscious entity.
Objects were felt by the right hand only (unseen by the participant).
What they could/ couldn’t do.
What does this tell us.
Info went to left hemisphere.
Couldn’t understand.
Not good at spatial- left hemisphere doesn’t understand touch.
Objects were felt by the left hand only (unseen by the participant).
What they could/ couldn’t do.
What does this tell us.
Info went to right hemisphere.
They could draw what they felt.
They couldn’t describe what they felt.
Right hemisphere understands feelings/touch.
