Core study nine-Sperry (Biological area)

Question 1

Background Sperry

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

Lateralization of Function

Answer 2

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

Question 3

Corpus Callosum

Answer 3

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

Question 4

Contralateral Control

Answer 4

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

Question 5

Commissurotomy

Answer 5

Surgical operation to sever the corpus callosum

Question 6

Visual processing

Answer 6

Our vision is slightly different. In each eye, we have two visual fields (LEFT and RIGHT)

Our left visual field (LVF) in both eyes sends information to the right hemisphere of the brain
Our right visual field (RVF) in both eyes sends information to the left hemisphere

Question 7

Aim

Answer 7

To study the functions of separated and independent hemispheres

Question 8

Sample

Answer 8

Epileptic-11 patients who had undergone a commissurotomy as a treatment for their epilepsy. They were obtained from a surgery within America.
Non epileptic- They were compared with a group of people who had not undergone the surgery.

Question 9

Why did sperry select the sample

Answer 9

Able to test the hemispheres independently as they were separated in the surgery

Question 10

Weakness of the sample

Answer 10

Small sample size
2 people had the surgery 4-5 yrs ago so may have recovered
Perhaps the cause of results was epilepsy

Question 11

Control of the experiment

Answer 11

Symbols displayed
Images displayed
Objects used
Fixation point
1/10th second time for presentation
Hands out of view
One eye covered
Tachistoscope

Question 12

Objects were presented in the right visual field

Answer 12

Information went to the Left hemisphere
Participants can describe it in speech and written format

Question 13

Objects were presented in the left visual field

Answer 13

Information went to the Right hemisphere

Participants insist that they’ve not seen anything- so couldn’t describe it verbally but if asked to point to a matching object on the table with their LEFT hand they can do so- still insisting they didn’t see anything

Question 14

Different visual stimuli were presented simultaneously to different visual fields (e.g. an image of an apple to the left vf; an image of a key to the right visual field), and the participant was asked to draw with his left hand (out of sight) what he had seen

Answer 14

Image of an apple went to the right hemisphere

Left hemisphere when an image of a key

The participants were able to draw an apple (LVF) but not consciously know why. Participants were Able to name object once they had seen the drawing in the RVF.

Able to say they had seen a key (RVF)- but unaware of anything else.
Were not sure why they had drawn apple

Question 15

Simple mathematical problems were presented to the left visual field.

Answer 15

Information went to the Right hemisphere
Participants Were able to sort objects by shape, size, texture- using their left hand.

Question 16

A nude pin-up was presented to the left visual field

Answer 16

Information went to the right hemisphere
participants would giggle/look embarrassed when nude picture appeared but they could not say what they were giggling/embarrassed about

Question 17

Objects were felt by the right hand only (unseen by the participant)

Answer 17

Information went to the Left hemisphere
Participants described object BY NAME in speech and writing

Question 18

Objects were felt by the left hand only (unseen by the participant)

Answer 18

Information went to the Right hemisphere
They could find the object with their left hand - by touch – in a bag full of objects.

When the objects were placed in one hand, they could point to what the object was-with the same hand which had held the object.

Couldn’t use speech to describe object - made wild guesses-seemed unaware of object in their hand – as they had no conscious awareness of it.

Question 19

Conclusions of the right hemisphere

Answer 19

Right hemisphere does not have language ability. Can show NON-VERBALLY that mental processes from left visual field and left side of body are present
Right hemisphere can process mathematical/spatial information
Non-verbal response suggested the right hemisphere has a second conscious entity

Question 20

Conclusions about the left hemisphere

Answer 20

Left hemisphere can communicate anything from the right visual field, or experiences of the right side of the body

Question 21

What ethical guidelines did Sperry uphold

Answer 21

The study was conducted ethically as the participants consented to be studied, no deception was used and they were neither harmed or overly stressed by the experimental tests.

Question 22

What ethical guidelines did Sperry break

Answer 22

Protection form harm- the participants may have been embarrassed that they could not say the words if they were presented to the left side.

Question 23

Ethnocentrism

Answer 23

On the one hand, since brain lateralisation is affected by the anatomy and physiognomy of our brain, we could argue that Sperry’s study is not ethnocentric as it was investigating a species- specific behaviour. There is no reason
to suppose that a sample of split-brain patients in America would perform any differently on these
tasks from samples of split-brain patients from other countries or cultures.

On the other hand, Sperry notes that there were individual differences and exceptions to the rule in the split-brain patients. Our
environment and culture influences affects how our brain develops, so it might be that people not raised
in a Western environment might show differences in their brain lateralisation. Without cross-cultural
confirmation of Sperry’s findings, this would be hard to establish, however.

Question 24

Internal reliability

Answer 24

It was a standardized procedure as it was a step by step procedure which can be repeated is needed to suggest a consistent (reliable) effect.

Question 25

External reliability

Answer 25

There was a very small sample of eleven patients with split brain so cannot be generalized to the wider population as it could be a fluke.
As well as ‘abnormal’ brains (split brain) cannot really be generalized to normal brains.

Question 26

Internal validity

Answer 26

Low risk of demand characteristics as not sure which hemisphere the information was being sent too.
The study controlled exterenous variables for example they were completely silent throughout the experiment so that no other information cannot be sent to the hemispheres

Question 27

Population validity

Answer 27

The sample was eleven participants who were all from America who had undergone a commissurotomy as a treatment for their epilepsy therefore only representative of abnormal brains .

Question 28

Ecological validity

Answer 28

The visual tasks lacks ecological validity because it does not resemble real life as person with a severed corpus callousm who had both eye open would be able to compensate, and the information would be received by both hemisphere at the same time

The tactile tasks are more ecologically valid as they resemble real life- every time we root around for something in our pockets or handbag we feel things with one hand without being able to see what we feel.

Question 29

Links to debates

Answer 29

Sperry’s work was ground-breaking in beginning to understand the physiognomy of the brain; that is,
how the brain works. It revealed the importance of the corpus callosum as a pathway for internal communication between the two sides of the brain. This can be seen as intrinsically useful.

Reductionist because it only looks at one factor to explain human behaviour and establish cause and effect. That the left hemisphere can communicate anything from visual right field and language.

Nature because it is investigating regions of the brain and investigating regions of the brain and lateralisation of brain function. Specifically, it demonstrated the
importance of the corpus callosum as a communication

Question 30

What area does it link to

Answer 30

Sperry’s study falls within the biological area as it is investigating regions of the brain and lateralisation of brain function. Specifically, it demonstrated the
importance of the corpus callosum as a communication pathway between the left and right hemispheres and provided evidence of the different functions each hemisphere performs.