BIOLOGICAL-Sperry Flashcards
What was the background to Sperry’s study?
Sperry had investigated the separated hemispheres of cats and monkeys. He could teach one hemisphere one thing while the other was unaware.
What does lateralisation of function mean?
Each hemisphere of the brain has a different function
What is the corpus callosum?
The bundle of nerve fibres that allows communication between the two brain hemispheres
What is contralateral control?
Each hemisphere contains the opposite side of the body and the opposite visual field
What is a commissurotomy?
Surgery which cuts the nerve fibres between the two hemispheres
What did Sperry aim?
-To investigate the function of each hemisphere of the brain
-Also wanted to investigate the effect of deconnecting the two hemispheres of the brain
Describe Sperry’s sample
-11 participants who have had a prior commissurotomy
-All had a history of severe epilepsy which wouldn’t respond to drug therapy
-Two had their surgery much earlier, and the other nine had it recent to the study
What controls did Sperry use in the study?
-All had to remain in silence for the duration of the study
-The images were only presented for 1/10th of a second
-In the tactile task, objects were not seen
What were the two tasks Sperry gave the participants?
TACTILE
-Objects are felt behind a screen
-Participant is asked to identify the object(name, point to, draw)
VISUAL
-Images flashed for 1/10th of a second to one side of the screen(left visual field, right visual field)
-Participant then had to identify the image
-Sometimes two images are flashed simultaneously
What were the visual results?
Flashed to the right visual field:
-Information went to the LHS
-They could name it, point to it with their right hand, and find it with their right hand
Flashed to the left visual field:
-Information went to the RHS
-Point to it with only their left hand, draw with their left hand, point to it with their left hand
-They couldn’t say what they had seen
Two different objects flashed to both visual fields:
-An apple was flashed on the left and went to the RHS, and a key was flashed on the right and went to the LHS
-They could draw the apple with their left hand, but would say they had seen a key
-They couldn’t explain why they had drawn an apple
Maths problems flashed to the left visual field:
-Info went to the RHS
-They could do the problem, either by pointing to or writing it
A photo of a nude pinup was presented to the left visual field:
-Info went to the RHS
-They would grin or giggle, but couldn’t explain why
What were the findings for the tactile task?
Objects were felt by the right hand only (unseen):
-Info went to the LHS
-They could name the object or point to it with their left hand
Objects were felt by the left hand only(unseen):
-Could point to it
-They could not name what they had felt
What did Sperry conclude?
The left hemisphere controls speech, writing, language and the right visual field and the right side of the body\
The right hemisphere controls the left visual field and the left side of the body, and able to communicate info non verbally.
Evaluate Sperry’s study in terms of ethics
Upheld
-Consent, as the participants volunteered
-Sperry didn’t deceive the participants
-None of the participants were harmed
-Confidentiality was upheld as participants were only referred to by initials
How is this study related to ethnocentrism?
Species specific as it is measuring anatomy
Individual differences in patients with a split brain, people may have differences in their brain lateralisation
How does Sperry’s study relate to internal reliability?
All participants completed the sample visual and tactile tasks with the same conditions. e.g all images flashed for 1/10th of a second
How does the study relate to external reliability?
There were only 11 participants, so a consistent effect may not be established as they may be a fluke, but it may not matter as it is a biological study so individual differences may be unrelated
How does this study relate to ecological validity?
-A person with a severed corpus callossum would have both eyes to compensate in real life, unlike the study
-Tactile tasks were more ecologically valid as when we root around in a pocket we are feeling things we can’t visually identify
How does the study relate to population validity?
The sample was extremely small and limited, and so can’t be generalised to the “normal brain”
How does the study relate to construct validity?
The differences in normal and severed brains could be related to the nature of their disorder, or the medication trying to treat it. May not be due to the commissurotomy
Very highly controlled, so EV may not be present
How does Sperry’s study relate to the debates?
Free will determinism
-Biological determinism as undergoing the commissurotomy will no longer be able to identify the objects they touch with their hands out of sight
Usefulness
-Groundbreaking findings allowing understanding of how the brain works
Reductionism vs Holism
-Only focuses on reductionism as an explanation for their behaviour ( split half procedure)
