Sperry - Whole study including evaluation and links PDF

Preview

Summary

Whole study including evaluation and links...

Description

Biological Area: Sperry Background information Sperry was investigating regions of the brain and wanted to look at how the brain works and how different parts of the brain can influence our behaviour. He wanted to investigate the role of the corpus callosum and find the functions of the left and right hemisphere. He based his experiment on a previous experiment by Vogal and Bogen. These are the people who originally performed the split of the corpus callosum on people. Patients would have this operation if they had epilepsy and severe seizures that were not responding to drug therapy. The split did not cure epilepsy, just made the fits less severe because it meant that they could pass into the other hemisphere. Sperry wanted to find out what the patients could and could not do, which would then tell him to roles of each hemisphere. Sperry investigated a small number of people who had previously had their corpus callosum severed. In a series of experiments, Sperry was able to demonstrate the functions that each hemisphere is responsible for. Key definitions Split brain / hemisphere deconnection: This is an operation which involves splitting the corpus callosum so that the right and left hemisphere are no longer connected. This will mean that nothing will be able to pass from one hemisphere to the other. Therefore, a fit won’t pass across from one hemisphere to another so the severity is lessened. It only takes place if the epilepsy is severe and the patient is not responding to drug therapy. Contra-lateral control: The brain is divided into two halves, called hemispheres. The left hemisphere controls most of the righthand side of the body and the right hemisphere controls most of the left-hand side. We now know that the right is in control of the spatial ability, face recognition and creativity and the left is in control of language, logic and understanding. Aim Sperry’s aim was to investigate the effects of hemisphere deconnection and to further understand the functions of the left and right hemispheres. He wanted to see if people could still complete daily functions after having their corpus callosum severed. Participants There were 11 participants who had already had their corpus callosum split. All participants had a history of severe epilepsy which had not responded to drug therapy and were right handed. Two of the patients had been operated on successfully sometime before the experiments but the other nine had only recently undergone the surgery. Research method Quasi Experiment and why: The participants had already undergone the surgery so it was a naturally occurring IV. It wasn’t completed in the participant’s own environment either. The IV is the deconnection and there is no control group.

Series of case studies and why: Research involved intensive study of 11 patients to investigate their behavioural symptoms resulting from the surgery. They were case studies of the individuals which came from old laboratory experiments.

Strengths and weaknesses of quasi experiments Strengths:  Enables researchers to look at things not practical or ethical  High ecological validity Weaknesses:  Hard to control extraneous variables  Hard to replicate

Strengths and weaknesses of case studies Strengths:  Allow in depth background information  Carried out for rare cases where large samples are not available Weaknesses:  Not necessarily generalizable  Not always scientific

IV DV Presence of the split brain. Each experiment had Naming objects, recognising objects and drawing their own IV for what they were testing (e.g. left or objects. right hand). Materials In this study, Sperry did 4 different trials and used different materials for each. Screen to cover hands; translucent screen; visual stimuli; computer; objects; pen; tray; nude picture; and geometric shapes. Procedure 1. Visual Field Only Image presented to RVF only

Image presented to LVF only

2. Tactile Investigation Object placed into right hand

Object placed into left hand

3. Visual and Tactile Investigation Image presented to RVF Image presented to LVF

4. Right Hemisphere test

Geometric shapes shown to both visual fields. Nude image only shown to LVF

Results  Can name the image they have seen (as it is within the left hemisphere that has language ability)  Can point to and find the object from an array of items with their right hand  Can draw the image with their left hand  Can find the object from an array of items using left hand  Cannot name it (because the image is ‘stuck’ in the right hemisphere and only the left has language ability)  Can name and describe the object  Can find the object again using their right hand if it’s placed into a bag of other objects  Cannot find the same object with their left hand  Can name and describe the object  Can find the object again using their right hand if it’s placed into a bag of other objects  Cannot find the same object with their left hand  Can find the item from an array of different items using the right hand  Cannot find the item using the left hand  Can find the item from an array of items using the left hand  Cannot find the item using the right hand  Participants blushed, giggled and seemed embarrassed, but did not seem to know why  Blushing and giggling is a non-verbal response and is believed to ‘give away’ what they had seen, because the right hemisphere cannot produce speech to answer the question directly  Don’t know why they are blushing. The right saw nudes but can’t talk so acts to show this such as blushing

2 controls and why they are used The amount of time that the images appeared on the screen needed to be controlled so that they could compare all the results. Also, so that the other side of the brain didn’t begin to start working. Another control was using the same images, because some images could trigger the other side of the brain and also, they wanted to be able to compare the results from each participant so it could be that the brain reacts differently to different images. Also, they also all had to do the same tasks to remove the extraneous variable that their brains are different and more adapted.

Conclusions (two of these) Sperry concluded that the left hemisphere is the most dominant in most people. This was because language skills are based in the left as well as the ability to speak. He also concluded that severing the corpus callosum stops the two hemispheres from communicating so they have their own stream of consciousness and memory. Language is necessary to recognise and name objects. Evaluation (add context to your point) Strength

Research Method

Data Type

   

     

Validity

Reliability

   

Very ethical Good to have case studies Opportunity sampling Could investigate variables that aren’t normally investigated

  

Had both types of data Could analyse data easily Used for comparisons Could see experiences of the participants

 

High face validity Tactical tests similar to real life so some ecological validity



Standardised Replicable due to controls High control Detailed results



How it is

Ethical Issues?

Sampling Bias

Weakness





  

 

Didn’t get a lot of qualitative data Could have asked them why they picked that or why they thought this was right Could have guessed answers Could be individual differences in brain lateralisation Low ecological validity People could have been guessing Only generalizable to people with the split brain Hard to replicate due to the participants’ conditions Small sample Different lengths of time since they had the surgery

How it isn’t

     

Informed consent No deception Right to withdraw Confidentiality Debrief Ethical way to gather participants





Good sample considering the rarity of the operation Close on genders

 



No control groups Small sample Couldn’t compare to a normal human brain Less control of extraneous variables



 

Protection of participants - only being shown the nude picture, could be uncomfortable Frustration

Small sample size Different lengths of time that they had had the surgery All English Not equal amount of male and female



Ethnocentrism

  

Culture and environment affects brain development Only one culture Family values will also change the brain Language you speak could affect the brain



 

Brain lateralisation is affected by the anatomy and physiognomy of our brain Species - specific Everyone has similar brain

How does Sperry link to the key theme Regions of the brain looks at different parts of the brain and their functions, such as the inferior frontal gyrus, which is involved in the cognitive control process and the ventral striatum, which receives input from other brain regions. Sperry was investigating the effects of hemisphere deconnection on different tasks and wanted to understand the functions of the right and left hemisphere. The participants took part in different test, which included; visual tests, tactile tests, a combination of visual and tactile tests and tests on the right hemisphere. Results showed that if an image is presented to the RVF then you can name it but if it is shown to the LVF then you cannot name it. How does Sperry link to the biological area The biological approach attempts to explain human behaviour through an understanding of biological and neurological processes. This approach assumes that all behaviour has a biological basis, meaning all behaviour can be explained by our biology. Sperry was investigating the effects of hemisphere deconnection on different tasks and wanted to understand the functions of the right and left hemisphere. The participants took part in different test, which included; visual tests, tactile tests, a combination of visual and tactile tests and tests on the right hemisphere. Results from the experiment show that language happens within the left hemisphere so you can only describe an image if it is presented to the RVF. It also proved that the left hemisphere is the more dominant hemisphere. He also proved that separating the two hemispheres means that they can no longer communicate with each other....