A study in consciousness
Book review by Anthony Campbell. The review is licensed under a Creative Commons License.
This is a book about consciousness, and specifically about the "hard question": how is it that events in the brain give rise to subjective experience? It is a sequel to Humphrey's earlier monograph A History of the Mind but adds a lot of new ideas. The book is short, unlike most of those on this subject, but, like everything that Humphrey writes, it packs more into its small compass than you will find in other books that are three or four times as long.
The title "Seeing Red" refers to the visual experience we describe in that way, and Humphrey starts by dissecting what happens when we look at a red field. He identifies four components. First, there is the raw sensation ("redding"). Next, there is the subject's awareness of this sensation, perhaps accompanied by feelings of pleasure or dislike. Then the subject registers the fact that the red screen is out there. Finally -- and this Humphrey takes to be important -- the subject comes to experience himself as an experiencer.
Although these four things normally occur simultaneously, they can be separated, as happens in the remarkable phenomenon called blindsight, which was first described some forty years ago in a monkey by Humphrey himself. It is now known to occur in human patients as well as in animals.
Humans who have suffered damage to the visual cortex in their brains are blind, in the sense that they do not report any visual experience, but they do have a kind of unconscious vision that allows them to locate objects and guess their colours with some accuracy. This is evidence that consciousness is not necessary for at least some sort of vision: sensation and perception can be separated. Humphrey suggests that, even in normal people, sensation and perception may really be separate: "sensation and perception, although they are triggered by the same event, are essentially independent takes on this event, occurring not in series but in parallel, and only interacting, if they ever do, much further down the line."
This brings us to the notorious philosophical question about the purpose of consciousness: what, if anything, is it for? Could we do without it? Humphrey's answer is that it is what gives rise to our sense of identity. Patients with blindsight, Humphrey says, do not feel personally involved in what is happening. So sensation may be involved in the production of selfhood, and this, he suggests, is the "point" of consciousness. But why should it have been selected for during evolution?
This leads to a discussion of the linkage between sensation and action, which was the subject of Humphrey's earlier book on consciousness. Initially in the course of evolution, sensation would have led more or less directly to action, but gradually action became internalized and detached from its external expression. We can imagine a process of progressively more complex mirroring of the external world within the brain, and such a representation of the world would be expected to have survival value.
So far, so good, but Humphrey does not claim to have solved the "hard problem" at this point. Something else is needed, and he suggests that this may be connected with the nature of time. Here he has a fascinating discussion of what he calls the "extended present" or "temporal thickness". At this point I was reminded of Julian Barbour's notion of "instants of time", as discussed in his book The End of Time. I have long suspected that the solution to the mystery of consciousness may be bound up with the nature of time (or, if Barbour is right, the non-existence of time).
Why is it that we find it so difficult to shake off the notion of mind and body as separate entities? Humphrey's suggestion is that this belief, illusory though it is, has been programmed into us by natural selection. What makes human beings so successful "is nothing less than their conviction that as human souls they have something extra-special to preserve, even beyond death." And (although Humphrey does not discuss the idea) is this in turn the reason why all human societies we know of have had some form of religious belief?
I am not sure that Humphrey has fully succeeded in explaining consciousness, but this is certainly one of the best books on the subject that I have read.
1 August 2006
%T Seeing Red
%S A study in consciousness
%A Nicholas Humphrey
%I The Belknap Press of Harvard University Press
%C Cambridge, Massachusetts and London, England
%G ISBN 0-674-02179-7
%P 151 pp