Sperry (1968) Split brain studyintroduction• brain has 2 hemispheres• connected by commissural fibres• lateralisation of function – each has different functions – cognitive / motor• split to treat extreme epilepsy
Sperry (1968) Split brain studydesigns: 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
Sperry (1968) Split brain studyprocedure• 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
Sperry (1968) Split brain studyresults: visual test 1• subject show image in one visual field• recognised if in that field before• not recognised if re-shown in other field
Sperry (1968) Split brain studyresults: 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
Sperry (1968) Split brain studyresults: visual / drawing test• 2 objects shown 1in LVF, 1RVF• drew object with shielded L hand• reported they had drawn object in R field!
they could draw, When asked to with the left say what they hand, the object had drawn they (e.g. pen) that would name the had been object shown topresented to their their RVF (e.g. LVF. banana)!
Sperry (1968) Split brain studyresults: 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
Patients would feel one object with each hand When they felt When they feltand object with and object with the left hand the right hand patients could patients couldnot name object name the object (but couldidentify it non- verbally, byLeft handitcould picking out from a group) not respond to what the right hand felt
Sperry (1968) Split brain studyresults: 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!
Sperry (1968) Split brain studydiscussion: 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
Sperry (1968) Split brain studydiscussion: 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
Sperry (1968) Split brain studydiscussion• difficult to generalise!• variation even between only 11 subjects