Sperry 1968 on split brains - lateralisation

Question 1

Sperry - aim

Answer 1

• to record the psychological effects of hemispheric reconnection in patients with severe epilepsy
• to use results to understand how left and right hemisphere work in normal individuals

Question 2

Sperry - design

Answer 2

quasi experiment, snapshot study and controlled observation of split-brain patients, investigating their behavioural symptoms from hemisphere reconnection.
IV-presence or absence of split brain
DV-participants performance on various visual and tactile tasks.
-study can also be classed as series of clinical trials

Question 3

Sperry - sample

Answer 3

11 split-brain participants. Opportunity sample - patients were referred from White Memorial Centre in LA.
- for most patients, surgery reduced risk of frequency and severity of their seizures

Question 4

Sperry - apparatus

Answer 4

tachistoscope ( a device used to display images for specific amount of time ) used to test ppt’s abilities.
- visual stimuli were bcc-projected onto screen at a very high speed
-below screen was gap so ppts could reach various everyday objects but not see what their hands were doing.

Question 5

sperry - procedure

Answer 5

-ppts seated in front of screen + asked to focus on cross in middle of screen, one eye covered.
-images flashed on screen, for 0.1 second, so eye has time to process image in their visual field.
-tasks designed to test how right and left hemispheres respond to left visual field and right visual field and left+right hand.
TASKS USED TO TEST ABILITIES:
-visual and verbal task, puts shown one image to LVF and diff image to RVF, they are asked to say what they see/write what they see on screen
-visual material shown to one visual field only.Material to RVF only connected to left hemisphere so should be able to say what is there, because language centre of brain is in left hemisphere. material to LVF doesn’t link to language centre.
-visual and tactile task ppts asked to select an object from below screen to match what they see.
-dual processing tactile task, aka 2 task performed at same time, 2 objects placed simultaneously one in each hand and then hidden in a pile of objects, each hand required to recognise the objects.
-everyday life: ppts interviewed about everyday effects.

Question 6

sperry - results

Answer 6

1. VISUAL AND VERBAL TASK, DISPLAY $ TO LVF AND ? TO RVF
   -ppt reports he saw ? sign, showing RVF is linked to LH and right hand
   -ppt can draw $ sign its left hand, shows LVF is linked to left hand and RH
   2.VISUAL MATERIAL SHOWN TO 1 VISUAL FIELD ONLY
   -shown to RVF only: ppt can describe visual material in speech and writing as normal, RVF linked to LH and right hand
   -shown to LVF: ppt reports he saw nothing or saw flash of light on left
   -shown to LVF: ppt can select objects that are similar with left hand, e.g. select wristwatch when shown clock, showing language comprehensions in RH
   -picture of pretty women, ‘pimp’ to LVF: ppt giggles but says he saw nothing, shows emotional response from RH.
   3.VISUAL AND TACTILE TASK
   if object is placed in left hand ppt can only make wild guesses and may seem unaware that they’re holding anything.
   4.DUAL PROCESSING TACTILE TASK
   ppts right or left hand selects object presented to it, but each hand ignores other hands objects.
   5.EVERYDAY LIFR
   -ppts continue to watch TV or read books with no complaints:intellect and personality are unchanged, however short-term memory deficits and difficulties without concentration.

Question 7

sperry - conclusion

Answer 7

-functions are lateralised in the brain
-right hemisphere is ‘silent’ as it cannot respond verbally, it can respond with some emotion like giggling
-in a sense everybody has 2 minds in one body.