Choice and the split brain:
There is a bundle of nerves in the brain crossing the midline that permits the left half of the brain to communicate with the right half.  (David Wolman A Tale of Two Halves NATURE vol. 483 no. 483 March 15, 2012 page 260)  The name of the structure is the corpus callosum.  Strictly speaking there are other nerves that cross the midline, but for the cerebra, where we think we think, the corpus callosum is about the only way to chat. 

In years gone by it was occasionally necessary to cut the corpus callosum to treat epileptic seizures.  It had been observed that a seizure could start in one place on one side of the body.  The twitching could spread until the whole side of the body was involved.  Then the seizure could cross the midline.  As it did a full blown convulsion would occur with loss of consciousness, loss of muscle and sphincter control and often self injury.  Someone thought that if the corpus callosum was severed then the seizure could not cross the midline and the process would be interrupted.  Sometimes it worked.  Then one started out with a person who was incapacitated with recurrent seizures and wound up with a perfectly acceptable almost normal person.

Studies have been done on such people to demonstrate that yes, the two halves of the cerebrum cannot communicate in the usual way.  One classic was that they presented pictures so that one side of the brain saw one picture and the other side saw a different one.  In one case the left cerebral hemisphere was presented with a picture of a pretty girl.  The right side was shown a picture of a gorilla.  The researchers asked the patient wither there was anything odd about the picture.  The patient said no.  Speech is generally located in the left hemisphere, so it was that part of the brain that had answered.  Then the question was asked, “What is it.”

“A pretty girl,” said the left brain.  Then the patient laughed.  The right brain could not see the other picture, but had no problem realizing that it was a joke.  It had seen the gorilla and now knew there was a discrepancy.  When asked, the patient could not explain laughing.  The left hemisphere did not get it.

Similarly other tasks could be performed with the right hemisphere placidly introducing information unknown to the left.  The left hemisphere was not in the least troubled, but would make up an explanation for what had been done, say, by the hands.

So it seems that we are wired to make sense of the world and to make sense of what we have done.  If we have to make something up, we shall do just that. 

This of course plays straight into the issue of consanguinity and fertility.  The data I have offered elsewhere show that consanguinity determines the number of children.  And of course people usually say they had wanted however many they had actually had.  Perhaps so.  But if so, it was the issue of consanguinity that determined that desire, not some economic or social pressure. 

The impulse of the brain to make up explanations after the fact has been known for decades.  Still one read phrases like “a woman’s reproductive choices” is if such choices came spontaneously out of some operation of rational consciousness.  We have a long way to go.

There have been 70,348 visitors so far.

Home page