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
5. Sperry (1968) Split brain study
the studies: subjects
• 11 'most radical disconnection'
• 2 benefited; others 'recent'
6. 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
7. 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
8. 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
10. 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
11.
12. 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!
13. 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 to
presented to their their RVF (e.g.
LVF. banana)!
14. 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
15. Patients would feel one object with each hand
When they felt When they felt
and object with and object with
the left hand the right hand
patients could patients could
not name object name the object
(but could
identify it non-
verbally, by
Left handitcould
picking out
from a group)
not respond to
what the right
hand felt
16. 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!
17. 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
18. 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
19. Sperry (1968) Split brain study
discussion
• difficult to generalise!
• variation even between only 11 subjects
