I like short books. Better still, I like short books so packed with ideas that I have to stop and think on every page. Seeing Red is that sort of book. It is based on a series of lectures at Harvard University and is written in a simple and direct style, beginning with Nicholas Humphrey asking his audience to look at an expanse of red.
What does it mean to see red? Scientists can measure the light and the mixture of wavelengths, but seeing red is a subjective experience. So this apparently simple question throws us right to the heart of that great mystery - consciousness. In Seeing Red Humphrey brings together all his previous research and theorising to give us a counterintuitive and distinctly uncomfortable way of thinking about the nature of seeing.
A traditional theory of vision is that first we get visual sensations and then we use those sensations to perceive things in the external world. This is completely wrong, says Humphrey. Instead, he claims that sensation and perception are independent mental processes occurring in parallel, not in series, and have evolved for different functions.
Part of his reasoning comes from the strange phenomenonof blindsight. Back in the 1970s Humphrey worked with a monkey called Helen whose visual cortex had been removed. At first she seemed completely blind, but she eventually learnt to find her way around by vision. Subsequently, human patients were found who claimed to see nothing in part of their visual field but who could still make visual discriminations. In other words, they seemed to have perception without sensation.
The heart of Humphrey's theory is that seeing red is not a process of passively receiving impressions, or building up internal images, but something we do. He calls it redding. This means putting sensation on the production side of the mind rather than the reception side, a move that, he argues, has some quite unexpected and exciting implications. Sensation ought to be especially susceptible to top-down influences, to control by the person, or to being altered by drugs, which helps make sense of imagery and hallucinations. In addition, the active nature of vision might help one person simulate the mental states of another, so allowing for empathy and mind-reading.
And so we come to the nature of self. Humphrey claims that an experience is impossible without an experient and then shifts to the more interesting claim that an experient is impossible without experiences. So the self arises with sensations, and sensation is what makes consciousness matter.
This created self must be an illusion but, in a final twist, Humphrey tries to explain why we so readily believe in spirits, souls and inner selves. He suggests that belief in mind-body duality is an adaptation that has helped individuals live longer and more productive lives. Being deluded about our selves lies in our genes.
I am unsure about whether Humphrey has really said anything new and worthwhile about self and consciousness, but a book that makes me think so hard, in just 150 pages, is one I must recommend.
Susan Blackmore is visiting lecturer in psychology, University of the West of England.
Seeing Red: A Study in Consciousness By Nicholas Humphrey
Publisher - Harvard University Press
Pages - 151
Price - £12.95
ISBN - 0 674 02179 7