Discuss split brain research. Refer to examples of such research in your answer (16 marks)

Hemispheric lateralisation is the idea that both hemispheres in the brain are functionally different and carry out different mental processes. It also argued that the brain is contralateral - it operates in a diagonal way (ie. the left brain controls the right side of the body, and vice versa). However, some individuals have a "split brain" which means that the hemispheres cannot communicate and functions cannot be carried out. 

Sperry conducted a quasi experiment on 11 participants (10 men and 1 female) who had undergone a commissurotomy - the cutting of the nerve fibres, the corpus callosum, which separate the hemispheres of the brain - to treat severe epilepsy. Sperry used a general procedure but had four different variations: the main procedure aimed to see whether images shown to the right brain could be described orally. He found that due to the lack of corpus callosum, the hemispheres could not communicate and the image could not be described. Other methods included drawing what they could see in one visual field with the opposite hand, matching and describing faces and choosing similar objects based off of touch. Overall, Sperry was able to conclude that both hemispheres communicate with each other and perform different functions, and when communication is not possible, tasks become difficult or impossible. 

A strength of split brain research is that it has helped to develop understanding of the brain. Through Sperry's findings, other psychologists have developed the understanding that the left hemisphere is more analytical and relates to verbal tasks, whereas the right hemisphere is more geared towards spatial tasks and is more emotional and holistic in terms of language. This is an important development as it helps psychologists understand the differences between the hemispheres and their roles as synthesiser and analyser. However,  the differences in function may be too oversimplified as simply "verbal" or "non-verbal". Modern neuroscientists argued that hemispheric lateralisation is less clear than Sperry's research suggests, meaning that the findings have a limited application. This is important to consider when stating the importance of Sperry's findings, as it has potential issues surrounding reductionism. 

A weakness of split brain research is that it cannot be generalised. The participants in the study had a very specific type of split brain which was not a natural occurence. There may be differences between individuals with a natural split brain and those which are as a result of commissurotomy. An example of this is Kim Peek, who was born with brain damage which meant he had no corpus callosum. Despite having a low IQ and autism, he could read two pages of a book simultaneously, and had developed language centres in both hemispheres, showing differences between Peek who naturally had a split brain, and Sperry's participants. This is important as the findings should not be applied to the whole population as there may be differences. 

Another strength of Sperry's split brain research is that there is animal studies which support hemispheric lateralisation. Rogers conducted an experiment on chickens and found that they use their hemispheres differently - one in order to find food for survival, and the other to look for predators. This is good evidence to support hemispheric lateralisation as it suggests that animals have evolved to adapt their brains for survival, and that the hemispheres can act differently and simultaneously to perform different functions. However, this may not be the best support as animals and humans are very different in terms of biological makeup and brain structure. It could be argued that humans are more complex organisms than chickens and due to a lack of predators, do not need to be vigilant for survival purposes. This is important to consider as though Rogers provides evidence supporting hemispheric lateralisation, the evidence may not be effective as it is based on animal studies. 

A further strength of research into split brains and hemispheric lateralisation is that the method used was highly standardised, increasing reliability. Sperry's procedure was fully operationalised, and used precise timings (such as the image flashing for one tenth of a second, which ensured that the information was only in one hemisphere). This increases the reliability as it makes the procedure extremely standardised, and means it can be repeated with different individuals (those with natural split brains or not, due to other conditions, or in other cultures). This is important as it means that the evidence found can be reliable as it is easy to repeat.