The Biological Area

Key assumption: Biological mechanisms, brain functions and genetics play a key role in explaining behaviour.

The biological area uses highly scientific methods in order to understand biological processes such as hormone release, brain plasticity, brain activity and so on.

The biological area takes a rather reductionist and determinist view as it assumes that all behaviour is determined through a biological process which we cannot control.

Strengths Weaknesses

Year 1 studies:

Key terms:

Sperry (1986)

Area: Biological area

Key theme: Regions of the brain

Background

The brain has two hemispheres: the right and the left. Each hemisphere is thought to have different responsibilities. The left hemisphere is known to be responsible for language, logic and problem solving. The right hemisphere is known to be responsible for creativity, spatial awareness and emotion.

Key terms

1. Localisation of the brain – certain actions are carried out by specific parts of the brain (EG. Left hemisphere for language)

2. Lateralisation in the brain – there is a difference in roles between both hemispheres

3. Corpus Callosum – bridge between two hemispheres. The ‘bridge’ is a bundle of fibres which act as a communication pathway so that the two hemispheres can exchange information

4. Split-brain - When the corpus callosum is severed, information cannot travel from one hemisphere to the next… thus, splitting the brain into two singular hemispheres

Why would you want to severe the corpus callosum?

During an epileptic seizure, there is an electrical storm in one hemisphere of the brain which travels to the other. This causes the entire brain to be affected. In individuals with severe epilepsy where no other treatment helps, their corpus callosum would be severed. The idea behind this was that by severing the connecter between both hemispheres, the electrical storm could not transfer between hemispheres. This would limit the seizure and side effects. Individuals who have endured this surgery are considered ‘split-brain’ patients.

Case study: Phineas Gage

Phineas Gage was involved in a terrible accident where a mental pole went through his eye, brain and skull. Miraculously he survived this – he was conscious, speaking and even took himself to the hospital! After his injury, friends and family reported that Gage ‘was no longer Gage’. Doctors believed that the area of the brain which was damaged within Gages brain was responsible for planning, reasoning and control. This would explain why his personality changed. This supports brain localisation.

The brain and the body

The brains hemispheres are contralateral. This means that the left hemisphere controls the right side of the body, and the right hemisphere controls the left side of the body. This means that if someone has a stroke in the motor areas of their right hemisphere, it will be their left hand side of the body which is affected. And similarly vice versa.

Everything on the left of your nose is your left visual field. Everything on the right

of your nose is the right visual field.

Humans are cross-wired

Visual field and brain hemispheres – normal humans

As seen in the diagram at the side, any information from the right visual field enters both eyes (red). This information is then taken to the left hemisphere to be processed. In normal humans, this information is communicated to the right hemisphere. Similarly, any information from the left visual field enters both eyes (blue). This information is taken to the right hemisphere to be processed. In normal humans, this information is communicated to the left hemisphere.

Visual field and brain hemispheres – split-brain patients

See diagram below. However, in split brain patients their corpus callosum has been severed. This means the hemispheres do not communicate with each other. This means, information from the left visual field enters the right hemisphere (red). This information is not passed onto the left hemisphere due to split brain. In addition, this means information from the right visual field enters the left hemisphere (blue). This information is not passed onto the right hemisphere due to split brain. This means both hemispheres know different things.

Aim

Sperry believed split-brain patients revealed the ‘true’ nature of each hemisphere. His aim was to investigate the functions of each hemisphere.

Method

11 participants (10 male, 1 female)

Evaluate:

1. Sample size

2. Gender split

All participants suffered epilepsy. All participants had previously undergone their split-brain surgery. Participants had a mean of 5.5 years post-treatment when the study was conducted.

Quasi experiment

Why was this type of experiment conducted?

Laboratory experiment

Why was this type of environment used?

This study can be considered:

A case study – an intense study of 11 patients

A snapshot study – each split-brain patient was tested at one point in time and their behaviour monitored.

Each participant completes all tasks. This means the repeated measures design was used.

Independent variable (IV) - whether the individual has split brain (or not)

Dependent variable (DV) - the individual’s performance on each task

Note: There is only one IV in this study, as all participants had a split brain. Why is there no control group?

Procedure

Task 1: Visual task (sight)

Participants covered one of their eyes. The participant was asked to stare at a focal point on a screen. The researcher would project a stimulus on either the left hand side or the right hand side of the fixation point for less than one-tenth of a second.

Participants were then asked what they had seen. It was found that participants would only recognise the stimuli if the stimuli was presented again to the same visual field as it primarily was.

This means, if participants were shown stimuli in the right visual field, but then shown the same stimuli to the left visual field, they would claim to have not seen it before.

Why did this happen?

There is no corpus callosum to bridge the information from one hemisphere to the next.

Remember, the left hemisphere is responsible for language and for the right side of the body.

When information was presented to the right visual field, this was sent to the left hemisphere. When asked, the participants could describe what they had seen – in speech and writing with their right hand.

Why could they describe it in speech?

Because the left hemisphere is responsible for language

Why could they write with their right hand?

Because the left hemisphere controls the right side of the body

This means, when information was presented to the left visual field, this was sent to the right hemisphere. When asked, the participants would say they did not see anything or that they only saw a flash of light.

Why could they not remember what they had seen?

Because there is no bridge to cross the information from the right hemisphere to the left hemisphere. As the left hemisphere is responsible for language, there is no words for the person to say.

What could they do?

The participants could not draw what they had seen. Instead, they were able to recognise the stimuli by pointing to the image of what they had saw only with their left hand (as this is controlled by right hemisphere).

Summary for task 1:

What they saw in their right visual field went to what hemisphere?

Could they verbally describe this?

Why?

What they saw in their left visual field went to what hemisphere?

Could they verbally describe this?

Why?

Can they report seeing anything at all?

Task 2: Tactic task (touch)

This task measured participant’s recognition of objects through touch, in the absence of sight.

Participants would place their hands under the tachistoscope (see below). Each participant’s hands and objects were covered. This would allow them to touch a series of objects without seeing the objects. This was done as a control of variables, to ensure no visual stimuli would enter either hemisphere nor would it influence the results.

The researcher would place one object at a time into the participant’s hands. The participant would be asked what the object is.

Remember, objects placed in the right hand of the participant was processed by the left hemisphere. And objects placed in the left hand of the participant was processed by the right hemisphere.

When asked, the participants could recognise the object in their right hand. They were able to describe the object in speech and writing using their right hand only. Why was this?

When asked, the participants could not recognise the object in their left hand. They did not know what they were holding and could only guess. Why was this?

Summary for task 2:

From objects placed in the right hand, which hemisphere was information sent to?

This allowed the individual to describe in speech or writing OR guess?

Why?

From objects placed in the left hand, which hemisphere was information sent to?

This allowed the individual to describe in speech or writing OR guess?

Why?

Results: Combining visual and tactic

When shown a word on the right visual side, the individual is able to verbally identify what they have seen. This is because information from your right visual field is sent to your left hemisphere – where language and speech are controlled. The individual will also be able to write using right hand, as this is controlled by your left hemisphere.

When a word is shown to the left visual field, the individual is not able to verbally identify what they have seen. This is because information from your left visual field goes to your right hemisphere – there is no access to the language center here. The individual will appear to have ‘missed’ stimuli or report not seeing anything. The individual cannot write using left hand.

When information is shown to the left visual field, they may not verbally be able to report what they have seen or write a description of it. However, they will be able to draw what they have seen using their left hand – even if they aren’t sure of what they saw!

Conclusions

1. Split brain patients have ‘two brains’ which act independently

2. Perception in each hemisphere is independent. Information from one visual field or hand passes only to one hemisphere and is not available in the other hemisphere. If the information only passes to the right, the individual cannot respond in speech or writing

3. Split brain patients memory in each hemisphere is independent. Information from one visual field or hand is remembered only by that hemisphere

Evaluation

Research method

Type of data

Ethical guidelines

Validity

Reliability

Sampling bias

Practical applications

Ethnocentrism

Exam questions

1. Describe one finding from the visual tests used in this study. [2]

2. Describe one finding from the tactile tests used in this study. [2]

3. Outline how information was presented to the patient’s left visual field. (LVF). [2]

4. Explain why patients could not identify in words material presented to their LVF. [2]

5. Describe two ways having a split brain affected the patients performance on the tasks in this study. (4)

6. Describe what is meant by the term “hemispheric deconnection”. (2)

7. Describe how visual stimuli were presented to participants in this study. [4]

8. Sperry’s ‘split brain’ study investigated the psychological effects of hemisphere deconnection. Give one reason why the participants had previously undergone an operation to deconnect the two hemispheres of the brain. [2]

9. Outline one problem with generalising from the sample used in this study. [2]

10. Describe how split brain patients responded to visual material presented to their right visual field. (2)

11. Explain why a patient in this study was able to point with his left hand to pictures of images flashed to his left visual field. (2)

12. Explain how the findings of this research are useful in society? (2)