AQA Psychology for A Level Year 2 - Student Bk

1. Outline one research procedure used to investigate split-brain patients. [3 marks] 2. Briefly evaluate research using split-brain patients to investigate hemispheric lateralisation. [4 marks] 3. Discuss split-brain research. Refer to examples of such research in your answer. [16 marks] Check It Issues with generalisation As fascinating as the findings from these studies are, many researchers have urged caution in their widespread acceptance, as split-brain patients constitute such an unusual sample of people. There were only 11 who took part in all variations of the basic procedure, all of whom had a history of epileptic seizures. It has been argued that this may have caused unique changes in the brain that may have influenced the findings. It is also the case that some participants had experienced more disconnection of the two hemispheres as part of their surgical procedure than others. Finally, the control group Sperry used, made up of 11 people with no history of epilepsy, may have been inappropriate. Consider: Who may have made a better control group and why? Differences in function may be overstated One (perhaps unfortunate) legacy of Sperry’s work is a growing body of pop-psychological literature that overemphasises and oversimplifies the functional distinction between the left and right hemispheres. Although the ‘verbal’ and ‘non-verbal’ labels can, on occasion, be usefully applied to summarise the differences between the two hemispheres, modern neuroscientists would contend that the actual distinction is less clear-cut and much more messy than this. In the normal brain the two hemispheres are in constant communication when performing everyday tasks, and many of the behaviours typically associated with one hemisphere can be effectively performed by the other when the situation requires it. Consider: This is an example of plasticity in the brain. Explain some further examples of brain plasticity. Evaluation e X tra Concepts: The drawing abilities of the left and right hemispheres What the right hemisphere lacks in linguistic skill, it partly makes up for in terms of its superior drawing abilities. This has been shown in tests with split-brain patients. A picture is flashed to either their right or left visual field. As you can see in the drawings below, the left hand continually outperformed the right hand in such tests despite the fact that, for all the patients, the right hand was their preferred hand. Question Using your knowledge of split-brain studies, explain why this shows that the right hemisphere is dominant for drawing skill. @ookx hs Concepts: Kim Peek – a natural split-brain Kim Peek was not one of Sperry’s patients but was the inspiration for the 1988 Oscar-winning movie Rain Man , the story of a very high functioning autistic savant. However, Peek’s exceptional abilities, depicted in the film, were not attributable to autism . Rather, Peek was born with severe brain damage including a total absence of a corpus callosum. This meant that unlike Sperry’s participants, Peek’s split-brain was due to natural causes. Although socially awkward with a low IQ of 87, Peek’s powers of memory were prodigious. He had word-for-word recall of over 12,000 books. He could read two pages in around ten seconds, employing his split-brain to simultaneously read one page with his right eye and one page with his left. He knew phone books by heart, and could say what day of the week a particular date fell on going back decades. His party trick was to tell strangers the names of people who used to live next door to them years ago. Question It is likely that Peek had fully-developed ( bilateral ) language centres in both hemispheres of his brain which may explain some of his extraordinary abilities. How does this make him different from Sperry’s patients? @ookx hs @ookx hs Evaluation Demonstrated lateralised brain functions Sperry’s (and later Michael Gazzaniga’s) pioneering work into the split-brain phenomenon has produced an impressive and sizeable body of research findings, the main conclusion of which appears to be that the left hemisphere is more geared towards analytic and verbal tasks whilst the right is more adept at performing spatial tasks and music. The right hemisphere can only produce rudimentary words and phrases but contributes emotional and holistic content to language. Research suggests that the left hemisphere is the analyser whilst the right hemisphere is the synthesiser – a key contribution to our understanding of brain processes. Strengths of the methodology The experiments involving split-brain patients made use of highly specialised and standardised procedures . Sperry’s method of presenting visual information to one hemispheric field at a time was quite ingenious. Typically, participants would be asked to stare at a given point, the ‘fixation point’, whilst one eye was blindfolded. The image projected would be flashed up for one-tenth of a second, meaning the split-brain patient would not have time to move their eye across the image and so spread the information across both sides of the visual field, and subsequently, both sides of the brain. This allowed Sperry to vary aspects of the basic procedure and ensured that only one hemisphere was receiving information at a time. Thus he developed a very useful and well-controlled procedure. Theoretical basis Sperry’s work prompted a theoretical and philosophical debate about the degree of communication between the two hemispheres in everyday functioning and the nature of consciousness. Some theorists, for example Roland Pucetti (1977), have suggested that the two hemispheres are so functionally different that they represent a form of duality in the brain – that in effect we are all two minds (and that this is a situation that is only emphasised rather than created in the split- brain patient). In contrast, other researchers have argued that, far from working in isolation, the two hemispheres form a highly integrated system and are both involved in most everyday tasks. Split-brain research into hemispheric lateralisation 43 •