AQA Psychology for A Level Year 2 - Student Bk

Question 4 Discuss research using split-brain patients to investigate hemispheric lateralisation. (16 marks) Morticia’s answer Lateralisation is not the same as localisation but they can be easily confused. Localisation refers to the fact that specific areas of the brain have specific functions, whereas lateralisation refers to the fact that the two parts of the brain control different things, in other words they have different functions. The left half of the brain controls the right side of the body such as the right hand or right leg. The eyes are a bit different because each eye is divided into a left and right visual field and the left side of the brain processes the left visual field. The right side of the brain process the right visual field coming from both eyes. This was shown in a study by Roger Sperry. He used people who had their brains cut in half – called split-brain patients. The operation was done because they suffered from severe epilepsy and one way to treat this is to cut the connections between the two parts of the brain to stop the electrical signals going back and forth. This means that patients weren’t deliberately harmed just for this operation which would have been unethical. Sperry tested his patients a lot using quite a clever method so they could see images on a screen but couldn’t see what their hands were doing. This meant he could show images on the left part of the screen which are then processed by the left hemisphere. If the patients were then asked to select the same object they couldn’t because the left hemisphere doesn’t control the left hand. Another test that he used was to ask people to say what they saw on the screen. They could only do this if the object was on the left side of the screen because that is linked to the left side of the brain where speech is located. Words were flashed for a very brief time otherwise people could move their heads and then both halves of the brain would see the words. To evaluate this research we can think about ethics. It was unethical because the operation was done anyway. It was a good study because it involved real patients and the tasks were everyday tasks which could show what they could and couldn’t do. However, there are issues with generalising because the patients may have brain damage from their epilepsy. Also the control group should have had epilepsy as well rather than being normal. (403 words) These definitions are not really necessary for a question that focuses on ‘research’. Again, this second paragraph is not addressing ‘research’ and there is also an error – the left side of the brain does not process the left visual field. In paragraph 3 the answer begins to focus on evidence but unfortunately, although the description contains some accurate detail, it is muddled. Again, another error in paragraph 4 – objects projected on the right, not the left, would be named as this information is processed by the left hemisphere. The first two evaluative points in the final paragraph are not relevant. The last two are but could have been developed more. Right from the beginning Luke’s answer appears to be much more concentrated than Morticia’s. The description of lateralisation is relevant here in the context of Sperry’s research. Paragraphs 2 and 3 provide accurate descriptive detail and a brief conclusion that could be developed. In paragraph 4 the points are brief and could be further discussed, particularly the latter point. Paragraph 5 contains a very clear, fully elaborated discussion point, and the following paragraph is a relevant methodological critique. The answer ends with a well-made philosophical point and some detailed discussion. Luke’s answer In the 1960s, Roger Sperry conducted research using split-brain patients to reveal how the brain is lateralised, i.e. how the two hemispheres perform different functions. Split-brain patients undergo an operation (to treat severe epileptic seizures) where the corpus callosum and other structures which connect the two hemispheres are severed. This means that functionally the person has two separate brains. Sperry was thus able to demonstrate that speech was controlled in the left hemispheres and the right visual field was connected to the left hemisphere (and vice versa). He did this by briefly exposing images on a screen to the left and right visual fields. Patients could say what they saw in the right visual field but not the left visual field. He also demonstrated this using touch. The patient’s hands were placed under the screen and the patient couldn’t see objects that could be touched. A patient could select an item with his right hand that was displayed to the left but not right visual field. This shows that the right hand is connected to the left hemisphere. This research was very important in establishing how the brain is lateralised and led to a Nobel prize for Sperry. The research also suggested that the left side of the brain is more an analyser and the right hemisphere is a synthesiser. However, this rather simplistic idea of left- and right-brained behaviour has been criticised as not representing brain function accurately. More recent research has shown that the brain is more plastic than once thought and each hemisphere can take on some of the functions of the other if required. In addition, in ‘real’ life the two hemispheres work together. His research was very well designed and objective and controlled, which meant the abilities of patients could be demonstrated. The key feature was ensuring that information was only received by one hemisphere, which was achieved using the short exposure time. One of the implications of the research is the question of whether we actually have two minds, each of which is functionally different, or whether the two hemispheres normally work in unison and therefore we do have one mind. One limitation of this research is that the participants had experienced severe epilepsy. This may have caused brain damage, which might influence the connections in their brain. Therefore we may not justifiably generalise the findings to the brains of normal individuals. Sperry did have a control group of normal individuals but it might have been better to have a control group of epileptics who didn’t have a split-brain in order to see whether the differences were due to the split brain. (432 words) On this spread we look at some typical student answers to questions. The comments provided indicate what is good and bad in each answer. Learning how to produce effective question answers is a SKILL. Read pages 387–397 for guidance. practice questions, answers and feedback 57 •