Hemispheric Lateralisation

Question 1

AO1: Hemispheric lateralisation

Answer 1

The two hemispheres each have different functions and roles.

The left hemisphere is responsible for language, where the two main language centres are located, the Broca’s area, responsible for speech production and the Wernicke’s area, responsible for the understanding of language.

The right hemisphere is responsible for recognition of faces, places and objects and creativity and can only produce rudimentary words and phrases but contributes to the emotional context of what is being said.

Moreover, the brain has contralateral wiring. The left hemisphere receives information from the right visual field and controls the right side of the body.

The right hemisphere receives information from the left visual field and controls the left side of the body.

Question 2

What are the evaluations?
(2 + discussion each)

Answer 2

1) RTC - Case study EB
- low population validity

2) RTS - Sperry - Split brain
- Individual differences

Question 3

AO3: Case study

Answer 3

Research to contradict hemispheric lateralisation of the brain comes from a case study on a patient named EB. EB suffered from brain damage that resulted in the removal of his left hemisphere and therefore his language centres. Despite this, after some time EB managed to regain some of his language ability which would not be possible if the brain was completely lateralised. This demonstrates that language must be in more areas than just the left hemisphere. Therefore, lowering the validity of research into lateralisation of function in the brain.

Question 4

AO3: Discussion for case studies

Answer 4

The case study of EB lacks population validity. It may not be appropriate to generalise the findings on the lateralisation of function to the typical population, as these are unique case studies where brain damage may have affected the way in which the brain functions and some individuals may be able to process language in the right hemisphere. For example, some research has suggested that language is not solely lateralised to the left hemisphere but is found in the dominant cerebral hemisphere which is commonly found to be opposite to the dominant handedness. Therefore, suggesting that more research is needed with more diverse samples before firm conclusions on the lateralisation of language is possible.

Question 5

AO3: Split brain

Answer 5

Research to support hemispheric lateralisation was conducted by Sperry using split brain patients with a severed corpus callosum. He found that when participants were shown an image of an object to their right visual field, the patient could name it verbally but when presented to the left visual field they could not name it verbally but could identify the object through pointing. This supports that the brain is lateralised and that the hemispheres are responsible for different functions such as the left being responsible for language abilities. Therefore, increasing the validity of research into hemispheric lateralisation.

Question 6

AO3: Discussion - individual differences

Answer 6

One limitation of the research is individual differences in the participants, in relation to how lateralised their brain was. The degree to which the corpus callosum was severed for each participant varied greatly with some having a greater disconnection between the two hemispheres than others. This means that there may still be some ability to communicate between the two hemispheres. This is a weakness because the research may not be measuring the true effects of lateralisation because of this confounding variable, which reduces the internal validity of hemispheric lateralisation.