Sperry (1968) Split brain study

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Sperry (1968) Split brain study

• Hemisphere deconnection and unity in conscious
  awareness
• American Psychologist 23 pp723-33

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Sperry (1968) Split brain study

• introduction
• brain has 2 hemispheres
• connected by commissural fibres
• lateralisation of function
• each has different functions
• cognitive / motor
• split to treat extreme epilepsy

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Sperry (1968) Split brain study
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Sperry (1968) Split brain study

• the studies subjects
• 11 'most radical disconnection'
• 2 benefited others 'recent'

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Sperry (1968) Split brain study

• designs natural experiments
• variables occur 'naturally
• e.g. socio-economic- but in this case surgical
  procedures
• carefully controlled tests
• also case studies
• open ended interviews etc

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Sperry (1968) Split brain study

• procedure
• one hand feeling unseen objects
• attention to one visual field
• image shown for 1/10th sec (to prevent eyes
  moving to prevent use of other visual field)
• 2 images shown for 1/10th s one to each field
• etc

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Sperry (1968) Split brain study

• results visual test 1
• subject show image in one visual field
• recognised if in that field before
• not recognised if re-shown in other field

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Sperry (1968) Split brain study

• results visual test 2
• RH subjects shown objects in each field
• could describe object in R field
• said no object in L field, or just a flash'
• able to respond non-verbally (pick up object with
  L hand) to object in L field

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Sperry (1968) Split brain study

• results visual / drawing test
• 2 objects shown 1in LVF, 1RVF
• drew object with shielded L hand
• reported they had drawn object in R field!

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they could draw, with the left hand, the object
(e.g. pen) that had been presented to their LVF.
When asked to say what they had drawn they would
name the object shown to their RVF (e.g. banana)!
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Sperry (1968) Split brain study

• results tactile test
• objects in R hand gt verbal description
• object in L hand gt only NV response
• L hand unable to respond to stimulus in R hand

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Patients would feel one object with each hand
When they felt and object with the right hand
patients could name the object
When they felt and object with the left hand
patients could not name object (but could
identify it non-verbally, by picking it out from
a group)
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Sperry (1968) Split brain study

• results 'competing tasks'
• R and L hand had different tasks
• could do both at same time
• non-split brain subjects slowed by this
• only useful for odd lab tasks!

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Sperry (1968) Split brain study

• discussion Sperrys conclusions
• apparent doubling of most areas of conscious
  awareness
• hemispheres appear unaware of each other
• easier to think of two hemispheres as two people

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Sperry (1968) Split brain study

• discussion not a simple tale!
• R side could (literally) tell L side what it
  knew!
• in lab had to be prevented from talking
• sides not so isolated
• so personality / intelligence effects limited
• some STM / concentration difficulties

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Sperry (1968) Split brain study

• discussion
• difficult to generalise!
• variation even between only 11 subjects