Sperry, 1968 (Split Brain)

Question 0

What is the main bundle of nerve fibres that joins the two hemispheres called?

Answer 0

Corpus callosum (thick body).

Question 1

What is epilepsy?

Answer 1

A collection of disorders that are associated with uncontrollable seizures and electrical impulses.

Question 2

What animals had Sperry performed the split brain technique on?

Answer 2

Cats and monkeys.

Question 3

What is the left hemisphere connected to?

Answer 3

Right side of the body and right visual field.

Question 4

What is the right hemisphere connected to?

Answer 4

Left side of the body and left visual field.

Question 5

Which of the two hemispheres are connected to language?

Answer 5

Left hemisphere.

Question 6

What is the aim of study?

Answer 6

To investigate the psychological effects of hemisphere deconnection (in split brain patients) and the lateralisation of function.

Question 7

What is the method of the study?

Answer 7

Quasi Experiment/Case Study

Question 8

Describe the participants.

Answer 8

• 11 ‘split-brain patients’

- Undergone hemisphere deconnection due to epilepsy which could not be treated by medication.

Question 9

Describe the procedure.

Answer 9

The participant had one eye covered and was asked to gaze at a fixed point in the centre of a projector screen. Visual stimuli were back projected onto the screen either to the right or left at a very high speed (one picture every 0.1 second or less). This meant that the eye only had time to access the image in the visual field where it was placed. Below the screen was a gap so the participants could reach objects but not see his or her hands.

Question 10

What was the visual investigation?

Answer 10

It involved flashing one stimuli at a time to one visual field or two stimuli simultaneously to different fields and participants were asked to identify what they saw through speech, writing or drawing.

Question 11

What was the tactile investigations?

Answer 11

It involved placing an object in one hand, or the other, or both hands simultaneously without the participant being able to see what they were holding and then asking them to identify what they had been holding through speech, writing and drawing or manual selection from various objects.

Question 12

What is the IV in the study?

Answer 12

If they were a split brain patient or not.

Question 13

What is the DV in the study?

Answer 13

P’s performance on the tests.

Question 14

What are the results?

Answer 14

• A picture shown in one visual field is only recognised again if it appears in that visual field.
• Items presented in the right visual field (left hemisphere) could be described as speech and written.
• If the same items are then projected to the left visual field (RH) the participants says he did not see anything.
• If you then ask the participant to use his left hand (RH) to point to a matching picture or object in collection of pictures/objects, then he points to the item he has just said he couldn’t see.

Question 15

What can the right hemisphere do in split brain patients? (7)

Answer 15

• Human mental capacities
• Understanding of general categories
• Simple arithmetic problems
• Responding to spoken cues
• Sorting
• Spatial awareness
• Emotion

Question 16

What does the study show?

Answer 16

Patients acts as if they have two minds in one body. He established that the left hemisphere has language and the brain shows lateralisation of function. He acknowledges that there are individual differences between patients.

Question 17

What were the strengths of the method used?

Answer 17

• Quasi experiment: allowed researchers to investigate variables that they are not able to investigate in a lab experiment.
• Can be seen as a collection of detailed case studies conducted in highly controlled and objective laboratory equipment and procedures (reliable).

Question 18

What are the weaknesses of the methods used?

Answer 18

• No full control over IV.
• Low ecological validity (tests are not like real life).
• Test is artificial.

Question 19

How representative was the sample of participants?

Answer 19

• Small sample so lacks generisability but all Ps experienced similar effects.
• It may have been the epilepsy that had caused their brain functioning differently (hard to draw out conclusions).

Question 20

What type of data was collected?

Answer 20

• Quantitative: If something could be identified or not. (Data about different functioning of the two hemispheres.)
• Qualitative: Experiences of “split brain” patients. (Giggling at pin up pictures without knowing why they giggled.)

Question 21

Define: Lateralisation of function

Answer 21

How the two hemispheres have different functions.

Question 22

What would you change?

Answer 22

• Sample (11 Ps): Bigger sample means findings on lateralisation of function are more generalisable. However it will be more expensive and harder to organise as split brain patients are quite rare.
• Method (Quasi/Lab): Compare split brain patients (with epilepsy) with other people with epilepsy rather than the population who don’t have it. Removes epilepsy as am extraneous variable. We can see how IV affects DV but some people may not be willing to do it.
• Ethics: Protection- unaware their brains are functioning differently. Debrief them and answer any questions they may have.