An Experiment with a Split-Brain Subject

(Corpus Callosum severed, a treatment for epilepsy)


Left brain dominates for language, speech, and problem solving


Right brain dominates for visual-motor tasks

split2.bmp (45058 bytes)1.  Each hemisphere was presented a picture that related to one of four pictures placed in front of the split-brain subject.

2.  The left and right hemispheres easily picked the right card.   The left hand pointed to the right hemisphere's choice, and the right hand pointed to the left hemisphere's choice.

3.  The patient was then asked why the left hand was pointing to the shovel.  Only the left hemisphere can talk, and it did not know the answer because the decision to point to the shovel was made in the right hemisphere.

4.  Immediately the left hemisphere made up a story about what it could see --- the chicken.  It said the right hemisphere chose the shovel to clean out a chicken shed.

This reveals the left brain's interpreter in action!


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Source:  Gazzaniga, Michael S., "The Split Brain Revisited," Scientific American, July 1998