Sperry

Sperry

1. Method

   • Quasi experiment
   • DV was the participants ability to perform a variety of visual and tactile tasks
   • Could be considered a series of case studies

2. Aim

   • Investigate the effects of disconnection between the two brain hemispheres
   • To show the two sides had different functions and information could not be passed between hemispheres

3. Participants

   • 11 participants
     • Already undergone a commissurotomy
     • 2 had had the surgery a while ago
     • 9 had had recent surgery

4. Procedure

   • Visual
     • One eye covered
     • Gaze at a fixation point in the centre of the screen
     • Projected for 1/10 of a second
       • so the eyes didn't move and it go into the wrong visual field
     • Left of the fixation point
       • Right hemisphere
       • Left visual field
     • Right of fixation point
       • Right visual field
       • Left hemisphere
   • Tactile
     • Gap bellow the screen
     • Reach objects but not see their hands
     • Objects placed in left/right/both hands
     • Left hand
       • Right hemisphere
         • Visa versa
   • Undertook a variety of both visual and tactile tasks
   • Called a tachistoscope
   • Right hemisphere tests
     • Left visual field presented with an object
       • Pick out that object by touch
     • Image presented to the left visual field
       • Asked if they had seen anything
     • Sort objects with left hand
     • Solve maths problems in left visual field

5. Results

   • Visual
     • Information showed to one visual field was only recognised if shown to the same visual field
     • Info presented to the left visual field could not be described but could be pointed to using the left hand
     • Info presented to the right visual field could be described in speech or writing
     • If two figures were shown at the same time they would say they had seen the one in the RVF but draw with their right hand the one in the LVF
   • Tactile
     • Objects placed in the right hand could be described
     • When objects were placed in the left hand they seemed unaware they were holding anything
     • Objects felt by one hand could only be recognised by the same hand
     • When one object was placed in each hand and then hidden in a pile of objects each hand would find its own object and ignore the other hands object

6. Evaluation

   • Validity
     • Lacks population validity
       • Study of the abnormal brain may not be true to the normal brain
       • Different experiences prior to surgery may have made their brains different
       • Undergone major brain surgery
       • Hard to generalise
     • Exceptions
       • individual differences in brain lateralisation
         • Even in a small sample
     • Lacked ecological validity
       • Does not usually effect normal life
         • Use both eyes
         • Speak
       • Sperry was aware they led normal lives
         • Trying to find out what they could not do in controlled conditions
         • Did not try to generalise to real life participants
   • Reliability
     • Found general trends and similarities
       • Some findings are reliable
     • Exceptions to the trends
       • Challenges the reliability
   • Ethics
     • Completely ethical
   • Data
     • Qualitative
       • Detailed data
         • Show a pattern
         • Map brain lateralisation
       • Outliers and exceptions
         • Couldn't analyse the data
   • Sample
     • Very small
     • Hard to generalise
   • Ethnocentrism
     • Investigating a species specific behaviour
     • Environment and culture effects how the brain develops
     • People in western environments may show differences in brain lateralisation
   • Research Method
     • Ethical as they had already had the opperation
     • Highly controlled
       • Showed the two hemispheres clearly
     • Compared to normal people to ensure the differences were due to the lack of corpus callosum

7. Usefulness

   • Began to understand how the brain worked
   • Showed the importance of the corpus callosum in internal communication

8. Links to area/perspective

   • Investigating regions of the brain
   • Investigating lateralisation of function
   • Importance of the corpus callosum in communication between hemispheres
   • Different functions of each hemisphere

9. Links to key theme

   • shows the function of the corpus callosum
   • Showed the left and right hemispheres have different functions

10. Links to debates

    • Psychology as a science
      • Fulfils scientific criteria
      • Psychology is a scientific discipline
      • His work could be proven wrong (falsifiable)
        • Hard to get a sample
    • Free will/ determinism
      • Biological determinism
      • Inability to do certain tasks is determined by physiological factors