one brain or two?. roger sperry & michael gazzaniga rare and extreme cases of epilepsy, radical...

One Brain or Two?

Roger Sperry & Michael Gazzaniga

Rare and extreme cases of epilepsy, radical but effective treatment – cut the corpus callosum

Of 10 operations, 4 subjects agreed to further testing

Three Types of Tests

Visual abilities testPicture shown to one visual field

Tactile testFeel but not see object

Auditory testTold to reach in bag and find asked for object

ResultsVisual test –

Right visual field, said object

Left visual, saw nothingWhen asked to point to object in left field, did so with right hand

Conclusion: both “brains” see the object, only left hemisphere has language skills to say what they saw

Tactile test – Object in right hand, could say

Object in left hand, couldn’t say what it was

They could point to the same object from group in front of them

Vicki

CriticismsJarre Levy

Disputes pop culture ideas of being right-brained or left-brained

Two hemispheres necessary to do practically everything

Recent Applications As above, attempts to clarify the

misunderstandings and misapplications

Schiffer (1996) – hypothesized that MPD person has more-than-usual level of independence in one hemisphere, takes ‘control’ of consciousness, etc.