Biopsychology: Split Brain And Hemispheric Lateralisation Flashcards
What is Hemispheric lateralisation?
- A theory that two halves of the brain are functionally different, meaning that certain mental functions are lateralised to particular hemispheres.
What is Split brain research?
- Has been used to investigate hemispheric lateralisation.
- This research is conducted on split brain patients. These are people who have had the connection between their two hemispheres surgically severed, meaning they cannot communicate.
- The presentation of a visual stimulus is only shown in either the left or right hemisphere.
What case study that supports split brain research?
Sherry’s split brain research demonstrated some ways in which hemispheric lateralisation occurs. In one of the studies, split-brain patients were presented with visual images to the left or right visual field. When presented to the left hemisphere (via the right eye), the patients could describe what they saw. But when visual images were shown to the right hemisphere (via the left eye), the patients could not report what they saw, although they could select an appropriate matching object. The findings of this study sheds light on hemispheric lateralisation by showing how different functions
are lateralised or bi-lateralised. The fact that the patients could only verbally report on what they saw
with their left hemisphere provides evidence that language abilities are only lateralised to the left
hemisphere. This finding on the laterslisation of language to the left hemisphere is further supported by
research on localisation of function, which has shown how Broca’s area (responsible for speech
production) and Wernicke’s area (responsible for speech comprehension) are only found in the left hemisphere. However, this study also shows that both the left and right hemispheres can interpret
simple visual stimuli. This capacity is evident in the left hemisphere, as when patients could verbally respond to information shown to their left hemisphere (via the right eye). But it’s also clear the right hemisphere could interpret visual stimuli as if it lacked this ability, the patients would be unable to select appropriate matching objects. This study’s findings on hemispheric lateralisation are especially credible because of the way that Sperry was able to manipulate the independent variable (the visual stimuli) so that the functioning of each hemisphere could be tested independently. This precise control of the variables gives this research strong internal validity, making its conclusions on hemispheric lateralisation
very credible.
Why has split brain studies had issues with generalisation?
Split-brain research tends to involve small samples (Sperry’s original split-brain research was conducted on 11 split-brain patients) composed of participants who have undergone an extreme surgical procedure, usually as a last-resort treatment for severe epilepsy. Generalising from these small and unique samples is difficult. This means that split-brain research may not tell us that much how hemispheric lateralisation works in non-split-brain patients. Consequently, its findings on hemispheric lateralisation may lack population validity. However, due to the unique nature of the split-brain condition, researchers don’t really have a choice about relying on these small and, arguably, unrepresentative samples.
What is a strength with split brain research?
It’s methodology. E - Firstly, the research was conducted in a laboratory, under controlled conditions. Secondly, the standardised procedure allowed Sperry to present visual information to one eye, and therefore one hemisphere, at a time. The use of controlled conditions allowed Sperry to carefully control for situational variables and the standardised procedure meant that Sperry had close control over the independent variable. As a result, split-brain research has high internal validity. This helps ensure we can trust its findings on hemispheric lateralisation
