Excerpt from Chapter 8, 'Words from an overcoat pocket', of
Without Conscience by
Dr. Robert Hare
Who’s in Charge?
In most people the two sides of the brain have different, specialized functions. The left cerebral hemisphere is skilled at processing information analytically and sequentially, and it plays a crucial role in the understanding and use of language. The right hemisphere processes information simultaneously, as a whole; it plays an important role in the perception of spatial relations, imagery, emotional experience, and the processing of music.
Nature probably "arranged" for each side of the brain to have different functions for the sake of efficiency.(4) For example, it is clearly more effective for all the complex mental operations required to use and understand language to take place in one side of the brain than if they were distributed over both sides. In the latter case, information would have to be sent back and forth between the two hemispheres, which would slow down the processing rate and increase the chances of error.
Further, some part of the brain has to have primary control over the task; if the two sides of the brain were competing for this control, the conflict would reduce the efficiency of processing. Some forms of dyslexia and stuttering, for example, are associated with just such a condition: Language centers are bilateral--located in both hemispheres. Competition between the two hemispheres makes for a variety of difficulties in the understanding and production of language.
New experimental evidence suggests that bilateral language processes are also characteristic of psychopathy.(5) This leads me to speculate that part of the tendency for psychopaths to make contradictory statements is related to an inefficient “line of authority”-- each hemisphere tries to run the show, with the result that speech is poorly integrated and monitored.
Of course, others with bilateral language--some stutterers, dyslexics, and left-handers--do not lie and contradict themselves the way psychopaths do.
Clearly, something else must be involved.