Sperry

Question 1

Background

Answer 1

Epilepsy is a condition is brought on by abnormal electrical impulses discharging within the brain disrupting normal brain patterns.
In the 1940’s a treatment was developed called ‘Split Brain Surgery’ (called commissurotomy) that included the corpus callosum being cut so that the abnormal electrical impulses could not spread throughout the brain.
Sperry thought that patients who had undergone split brain surgery were perfect participants for research into what each hemisphere of the brain actually does

Question 2

Key Terms

Lateralisation of Function

Answer 2

One side/hemisphere of the brain has a different role from the other

Question 3

Key Terms

Corpus Callosum

Answer 3

Fibres that carry the majority of information between the two hemispheres of the brain

Question 4

Key Terms

Contralateral Control

Answer 4

The idea that each side of your body is controlled by the other side of your brain

Question 5

Key Terms

Commisurotomy

Answer 5

Surgical operation to sever the corpus callosum (a.k.a ‘Split Brian Surgery’)

Question 6

Aim

Answer 6

To study the functions of separated and independent hemispheres

Question 7

Sample

Answer 7

• 11 patients who had undergone a commisurotomy as a treatment for their epilepsy. They were obtained from a surgery in America
• They were compared with a group of people who had not undergone the surgery and were not epileptic

Question 8

Visual Fields

Answer 8

• Each eye has two visual fields
• Right visual field is linked to left hemisphere
• Left visual field is linked to right hemisphere

Question 9

Equipment

Answer 9

• Sperry used a tachistoscope to show participants images that lasted for 0.1 seconds (one eye was covered)
• The screen allowed an image to be shown to just one visual field, or different images to be shown to different visual fields
• The screen had a dot in the middle (called the fixation point) for participants to focus on
• The screen hid the participants’ hands from view, so they could hold and feel objects without seeing them

Question 10

Controls

Answer 10

• Symbols displayed
• Images displayed
• Objects used
• Fixation point
• 0.1 seconds time displayed
• Hands out of view
• One eye covered
• Tachistoscope

Question 11

Procedure & Findings

Image shown to RVF

Answer 11

Info goes to LH and they could say what they had seen

Question 12

Procedure & Findings

Image shown to LVF

Answer 12

Info goes to RH and they could draw/point to the object with their left hand but could not say what they had seen

Question 13

Procedure & Findings

Apple shown to the LVF and key to the RVF

Answer 13

Key goes to LH, apple goes to RH. They would say they had seen a key but their left hand drew an apple

Question 14

Procedure & Findings

Simple maths problem shown to the LVF

Answer 14

Info goes to RH and they could point to the answer with their left hand

Question 15

Procedure & Findings

Nude image shown to LVF

Answer 15

Info goes to RH and they giggle/look embarrassed but cannot say why

Question 16

Procedure & Findings

Object held with right hand

Answer 16

Info goes to LH and they could name what they felt or write it

Question 17

Procedure & Findings

Object felt with left hand

Answer 17

Info goes to RH and they could point to or find again the object with their left hand but they couldn’t say what they had felt

Question 18

Conclusions

Answer 18

• Left Hemisphere - Has written and verbal language ability and control the right side of the body
• Right Hemisphere - Can only communicate non-verbally and controls the left side of the body

Question 19

Evaluation

Ethics

Answer 19

• Informed Consent - Participants consented to participate following being approached through their hospital
• Confidentiality - Details of each particpant were kept confidential
• Protection from Harm - May have been upsetting or embarrassing to not have full capabilities or understanding of your behaviour
• Deception - Participants were fully aware of the research

Question 20

Evaluation

Ethnocentrism

Answer 20

The sample were obtained from a hospital in America (so highly ethnocentric) but the roles of each hemisphere should be universal to all humans so perhaps it doesn’t matter

Question 21

Evaluation

Reliability

Answer 21

• Internal Reliability - Procedure was very standardised so high (though 2 participants had the surgery 4-5 years ago so may have recovered)
• External Reliability - Sample perhaps not large enough to establish consistent effect

Question 22

Evaluation

Validity

Answer 22

• Internal - Perhaps the behaviour can be explained as a result of epilepsy, not the surgery (low construct validity)
• External (population) - The sample was very specific so perhaps not generalisable
• External (ecological) - The visual procedure was not very realistic as we see things for longer than 0.1 seconds so our brains could adapt. The tactile procedure was more realistic as feeling around and not being able to see your hands is relatively normal