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Sperry (1968) Split brain study

Sperry (1968) Split brain study . ‘Hemisphere deconnection and unity in conscious awareness’ American Psychologist 23 pp723-33 . Sperry (1968) Split brain study. introduction brain has 2 hemispheres connected by commissural fibres lateralisation of function

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Sperry (1968) Split brain study

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  1. Sperry (1968) Split brain study ‘Hemisphere deconnection and unity in conscious awareness’ American Psychologist 23 pp723-33

  2. 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

  3. Sperry (1968) Split brain study

  4. Sperry (1968) Split brain study the studies: subjects • 11 'most radical disconnection' • 2 benefited; others 'recent'

  5. 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

  6. 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

  7. 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

  8. Left visual field Right visual field

  9. 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

  10. 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!

  11. 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)!

  12. Sperry (1968) Split brain study results: tactile test • objects in R hand => verbal description • object in L hand => only NV response • L hand unable to respond to stimulus in R hand

  13. Left hand could not respond to what the right hand felt Patients would feel one object with each hand 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) When they felt and object with the right hand patients could name the object

  14. 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!

  15. Sperry (1968) Split brain study discussion: Sperry’s conclusions • apparent doubling of most areas of conscious awareness • hemispheres appear unaware of each other • easier to think of two hemispheres as two people

  16. 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

  17. Sperry (1968) Split brain study discussion • difficult to generalise! • variation even between only 11 subjects

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