Split brain research Flashcards
AO1: Split brain research
Aim: To investigate the effect of severing the connection between the two hemispheres of the brain on functioning. It is a natural experiment studied on 11 individuals who had had their corpus callosum severed due to surgery
Participants sit in front of a screen, while fixating their gaze on a spot in the middle of a screen. Participants were presented with visual information to either their right visual field or left eye visual field for 1/10th of a second.
They found objects seen in right visual field will be processed by the left hemisphere (due to contralateral wiring) which is responsible for language. This means that the split brain patients can name the presented object verbally and in writing. Objects seen in left visual field will be processed by the right hemisphere (due to contralateral wiring) which is responsible for recognition. This means that the split brain patients cannot name the presented object, but can recognise it by pointing.
In conclusion the two hemispheres of the brain have different abilities and functions; but only the left can produce language. The right hemisphere can recall and identify information but cannot verbalise this.
What are the evaluations for split brain research? (4)
1) Scientific methods
2) Individual differences in participants
3) Relationship hard to establish
4) RTC case study of EB
AO3: Scientific methods
A strength of the research into split brain is that it uses scientific methods, so uses scientific enquiry. This is because it is based on objective and empirical techniques such as controlled laboratory settings. These are used in order to identify which hemisphere of the brain is responsible for which task, for example the split brain patients were only able to say what they saw when the image was presented to the right visual field, which suggests the left hemisphere is activated during language tasks. Arguably, this increases the overall internal validity of hemispheric lateralisation research, therefore, raising Psychology’s scientific status.
AO3: Individual differences
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 split brain research.
AO3: Confounding variable
Another weakness of split brain research is that a causal relationship is hard to establish. The behaviour of Sperry’s split-brain participants was compared to a neurotypical control group, whereby none of the participants in the control group had epilepsy. This could act as a major confounding variable as any differences between the two groups could have been due to the epilepsy rather than the split brain, as the epilepsy may have caused unique changes in the brain that may have influenced the findings of how the brain is lateralised. Therefore, it is difficult to establish whether the participants’ cognitive abilities and lateralisation are due to the split brain or epilepsy, lowering the internal validity of split brain research.
AO3: Case study
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 using split brain patients to investigate the effects of lateralisation of function in the brain.
