|Better Than One|
by David Uing
We have known for more than half a century that if the link between the two halves of the human brain is severed, the separate halves reveal all the components of mindedness: perceptions, beliefs, desires, memories, thoughts and will. There are significant differences between the two minds of split-brain patients. The left mind uses language to report its perceptions, the right mind cannot. The right mind is good at visual tasks such as pattern matching at which the left mind is very poor. When the right mind acts on a perception unavailable to the left mind, that mind confabulates the reasons.
These differences provide a basis for assessing behaviour initiated by the intact brain. If someone confabulates about their reasons for action, then that action must have originated in the right mind. Wilson & Nisbett report an experiment in which subjects chose from a selection of five identical stockings. The subjects confabulated the reasons for their specific choice, indicating that it was made by the right mind (probably because there was no logical basis for a choice by the left mind).
If someone cannot report what they perceived or why they acted as they did, then that perception and action must be the responsibility of the right mind. A driver on automatic pilot has their left mind absorbed by problems at work and cannot remember or report their driving experience during this period. Nevertheless, it transpires that they had obeyed several sets of traffic lights. It requires a mind to recognise that a red traffic light means stop and to initiate that action, and this can only have been the right mind.
A man gets out of bed, gets dressed, picks up two letters, leaves the house, checks for traffic before crossing the road, walks to a post box and posts the letters. He returns home and goes back to bed. When he wakes up he has no memory of what he did – he was sleepwalking. But his actions – especially checking for traffic before crossing the road – are indicative of a mind at work, which can only have been the right mind.
This is some of the evidence for the presence of two minds in the human brain; but both this and the split-brain evidence have been largely ignored by both philosophers and psychologists. I explore the reasons for this dismissal of the evidence. I explore how duality of mind can be reconciled with unity of person. I contrast the claim of two minds with the Dual System Theory (which claims two systems in the human mind, one shared with animals and one uniquely human) and with three recent books about the roles of the two hemispheres in the human brain.
I end the book with thoughts about issues that require further thought. How can Freud’s id, ego and superego be reconciled with two minds? Do we have two minds at birth, or does the left mind develop during childhood? What are the legal implications of actions being initiated by the right mind, which cannot use language to explain itself?