Sperry's split brain research

Question 1

Hemispheric lateralisation

Answer 1

• brain is split into 2 symmetrical halves: left and right hemisphere
• some of our functions are controlled by a particular hemisphere
• each hemisphere does something different
• left side of the body is controlled by the right hemisphere and vice versa
• outer layer of both hemispheres = cerebral cortex

Question 2

Corpus callosum

Answer 2

a bundle of nerve fibres that connect the 2 halves
* a bridge that connects the 2 hemispheres
* allows info to be reveieved from one hemisphere and to be sent to the other hemisphere

Question 3

Sperry’s experiment

Answer 3

• 1968
• 11 split brain patients
• split brain patients have no corpus collosum to study if info truly goes from left visual field to the right hemisphere and vice versa
• procedure involved blindfolding one eye of patient and presenting an image to other eye which ensured that he knew which hemisphere was being used
• variation of tasks using this procedure allowed conclusions to be drawed about the functions of different hemispheres

Question 4

Summary/Results of Sperry’s research

Answer 4

• supports localisation of function
• left hemisphere connects to the right visual field
• right hemisphere connects to the left visual field
  left hemisphere- language centre, speaking, understanding speech
  right hemisphere- drawing, recognising, music and spatial skills

Question 5

Tasks in Sperry’s research

Answer 5

1. Describing what you see
2. Recognition by touch
3. Composite words
4. Matching faces

Question 6

Describing what you see

Answer 6

picture of an shown to patients right visual and left visual field seperately
* right visual field = ppt could easily describe what was seen
* left visual field = ppt couldnt describe it
* suggests that theres a lack of language centres in the right hemisphere
* language is processed in the left hemisphere

Question 7

Recognition by touch

Answer 7

when asked to use the left hand to select a closely matching object from bag, (behind hidden screen) they were able to do this
* patient couldnt verbally identify what they had seen but was able to understand what the object was using right hemisphere to select corresponding object accordingly
* right hemisphere is good at recognition

Question 8

Composite words

Answer 8

when 2 words were presented simultaneously, on either side of visual field, ppt would write and draw a word with their left hand and say the other word
* shows right hemisphere is superior in terms of drawing tasks
* shows that speech production is processed by left hemisphere

Question 9

Matching faces

Answer 9

when asked to match a picture of a face series of other faces, pictured processed by right hemisphere was consitently selected correctly, whilst picture on left was consistently ignored
when composite picure was presented the left hemisphere (right visual field) dominated when asked to verbally describe it whereas right dominated in terms of selecting a matching photo
* right hemisphere is dominant in terms of recognising faces

Question 10

Evaluation

Answer 10

• small sample size
• ethical
• reliable
• Kim Peek Case study

Question 11

Small sample

Answer 11

• sperry’s research only used 11 patients, all with a history of epilepsy
• argued that this may have caused unoque changes in brain that may have influenced findings
• eventhough there was a contol group of 11 with no history, this wasnt enough
• study cannot be generalised to wider population
• low in population validity

Question 12

Ethical

Answer 12

• natural experiment so IV naturally occurred
• only ethical way to investigate the isolation of hemisphere by conducting it on patients who already had there corpus callosum removed

Question 13

Reliable

Answer 13

• Sperry’s research is reliable and scientific
• it used a standardised procedure and operationalised variables which meant that it was easy to test the reliabiltiy

Question 14

Kim Peek

Answer 14

• born with severe brain damage including the total absence of a corpus callosum
• split brain due to natural causes
• socially awkward with a low IQ of 87
• memory skills were exceptional
• he could read 2 pages in 10 seconds, employing his split brain to simultaneously read one page with right eye and the other with his left
• criticism of sperry as it suggests language centres can develop in both hemispheres in the brain, not just the left