AO3 - Hemispheric Lateralisation

• Research to support hemispheric lateralisation was conducted by Sperry using split brain patients with a severed corpus collosum. He found that when participants were shown an image of an object to their RVF, the patient could name it verbally but when presented to the LVF they could not name it verbally but could identify the object through pointing. Supporting that the brain is lateralised and that the hemispheres are responsible for different functions such as the left being responsible for language abilities. Therefore, split brain research supports the theory of hemispheric lateralisation
• However, split brain research has been criticised due to individual differences in how lateralised the participants 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 is a weakness because the research may not be measuring the effects of lateralisation effectively which reduces the internal validity of the research. Therefore, research conducted on split-brain patients may not be appropriate for explaining hemispheric lateralisation.
• Moreover, 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, arguing against lateralisation of function in the brain.
• However, 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.