Sperry

• Background

  Sperry wanted to investigate lateralisation of function, which is the belief that the two hemispheres have different functions, the right is in charge of special awareness tasks and the left in charge of language

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  Through contralateral control, which is the belief that our brains are cross wired so the left hemisphere is in charge of the right side of the body and vice versa, this proves our hemispheres are constantly communicating.

  
  

  Therefore, the only people that Sperry could test this on were people who had had their corpus callosum severed through the process of hemispheric deconnection in order to reduce severe symptoms of epilepsy.

  
  

  Sperry was interested in investigating the behavioural impact of a severed corpus callosum, and whether it would impact the behaviour or these individuals.
• Aim

  To record the psychological effects of hemispheric deconnection and to find evidence for lateralisation of function in 'normal brains
• Sample

  - 11 people who had had the split-brain operation who previously had severe epilepsy

  - all p's had had procedure at various times before study, reducing consistency

  - opportunity sample, as Sperry used patients who had already had the procedure
• Apparatus

  - researchers used a tachistoscope, which projects visual stimuli onto a screen for a specified amount of time

  - images were projected to the right/left side of screen meaning they were seen by the left/right visual field of each eye

  - images projected to RVS are processed by the left hemisphere and vice versa due to contralateral control
• Research method

  - quasi experiment

  - IV = whether the participant had a split brain or not

  - DV = performance on visual + tactile tasks -> observations + notes were made of their performance
• Procedure

  - each participant was studied alone

  - participant had one eye covered + asked to look at a fixed point in centre of screen on tachistoscope

  - visual stimuli projected onto screen, either to RVS or LVS

  - images were shown for 0.1 seconds each (control)
• Results - visual tasks

  - when shown an image in RVF, image would be processed in left hemisphere (in charge of language) means they would be able to process/say + draw what they had seen

  
  

  - when shown an image in LVF, image would be processed in right hemisphere (in charge of spatial awareness) means they wouldn't be able to say the word but could draw it

  
  

  - when p's were asked to draw what they had seen they would draw the image from the LVF but if asked to say what they had seen they would say the image seen in RVF
• Results - tactile tasks

  - if item placed in right hand, identified with left hemisphere + write down with right hand

  - p's able to find objects by touch but only by the hand where the object was first placed = suggests 2 hemispheres are working separately so when they searched for object, they would only recognise if it was in the same hand
• Further results

  - hemispheric deconnection didn't appear to affect p's intelligence or personality (lateralisation of function + contralateral control)

  
  

  - effects of surgery, gave p's short-term memory deficits, fatigue more quickly in reading + limited concentration spans + orientation problems
• Conclusions

  - split brain patients appear to have two independent streams of consciousness = supporting the argument of lateralisation of function

  
  

  - people with split brains have two separate visual inner worlds

  
  

  - split brain patients have a lack of cross integration where a second hemisphere doesn't know what the first hemisphere has been doing
• Link to key theme of 'regions of the brain'


  Sperry clearly illustrated how the region of the brain, the corpus callosum, plays a major part in normal behaviour and if it is severed, there are behavioural changes.
• Link to biological approach

  The biological approach assumes that all behaviour has a physiological origin and a biological basis and is a result of our genetics which are inherited from our parents. (2)

  
  

  Sperry links to the approach as he illustrates how the behaviour of the 11 split brain participants was a direct result of the physiological origin of their severed corpus callosum, resulting in their hemispheres having no communication with one another.

  
  

  This led to findings such as, when an image was presented to the left visual field, they participants couldn't name the image as their right hemisphere couldn't communicate with the left which is in charge of language, outlining the biological basis of their behaviour. (2)
• Ethics (followed + broken)

  + informed consent = informed of the reasons why they were completing the task

  
  

  + deception

  
  

  + protection of p's (physical)

  
  

  - protection of p's = embarrassed + psychological harm could create confusion as to why they cannot 'say' what they had seen in their left visual field
• Reliability

  Internal:

  + highly standardised procedure

  -> eg. all p's complete exact same visual + tactile tasks in the same way using same scientific equipment eg. tachistoscope

  -> replicate with different people

  
  

  External:

  - quantitative data is not collected

  -> eg. data consists of qualitative notes + observations about p's behav on visual + tactile tasks

  -> difficult to make direct comparisons
• Validity

  Internal:

  + high control over EV's

  -> eg. asking p's to focus on the fixation point

  -> increases scientific nature + can determine cause+effect

  
  

  Ecological:

  - task is unrealistic

  -> p's in real life would be able to spend as long as needed to look at images = could manipulate their visual field

  
  

  Population:

  - sample is very small + consists of people who had previously had severe epilepsy = cannot be generalised to all split brain people
• Sample evaluation

  + used males + females

  
  

  + highly representative as all 11 p's had had spilt brain operation and had a severed corpus callosum meaning hemispheres cannot communicate

  
  

  - opportunity sample used

  
  

  - small sample

  
  

  - based on people with severe epilepsy so can only generalise to those 11 people
• Research method evaluation

  + highly controlled environment = reduce risk of situational variables

  -> eg. manipulating visual field by only showing each image for 0.1 seconds

  -> increased internal validity + scientific nature

  
  

  - study is a quasi experiment + IV cannot be manipulated

  -> eg. unable to fully isolate IV against individual differences (split brain patients may have more experience with such tasks)

  -> reduces internal validity
• Ethnocentrism

  conducted in western society = findings are only applicable to western ideas of medicine + biological psychology

  -> don't know whether split brain operation occurs in other cultures
• Nature v Nurture

  Nature:

  -> biological factors eg. severed corpus callosum can impact behav eg. left hemisphere allows us to process + use language which is an innate factor + basis of behav

  
  

  Nurture:

  -> p's may learn to overcome the restrictions of the split-brain operation in daily life by manipulating their visual fields
• Reductionism v Holism

  Reductionism:

  -> assumes that the severed corpus callosum is the sole cause of psychological + behavioural issues, ignoring environmental factors

  
  

  Holism:

  -> addresses situational factors as well as when p's are not in a controlled in which they can only see the stimulus for a controlled period of time, they will be able to manipulate their visual fields
• Determinism v freewill

  Determinism:

  -> performance on tasks could have been pre-determined by the split brain operation so their behav was out of control

  -> brain connections determine how we interact with the world, meaning we have little control

  
  

  Freewill:

  -> split brain p's have the chance to exercise their free will in everyday life as they could manipulate their visual field + perform all normal functions
• Scientific nature

  Scientific:

  -> high controls (cause + effect)

  -> standardisation (replicability)

  -> quantitative measures/scientific equipment (objectivity)

  
  

  Unscientific:

  -> qualitative data (subjectivity may cause misinterpretation of findings)
• Socially sensitive

  - stigma = around split brain people, highlighting that their brain is different to others/unable to perform certain functions, may cause marginalisation from certain activities

  
  

  + raise awareness of such behaviours + lateralisation of function, increasing the usefulness of findings = improve knowledge + help people with a split brain