How conscious are your qualia?

Consciousness used to be a taboo subject among scientists. Now every man and his dog seems to have a theory of consciousness, and to be willing to put that theory in print. In this brief and speculative volume, Alexander Cairns-Smith presents a variant of the "it must be something to do with quantum theory" story. The presentation is more popular science than tightly argued theory, and though the account is readable, evidence is thin on the ground.

Cairns-Smith views consciousness in terms of its subjective qualitative aspects - what it feels like to be conscious. Psychological and computational aspects of consciousness (such as its possible role in cognitive functioning and its intentional and self-referential properties) are ignored.

The principal argument on which the book is founded is that the qualitative aspects - qualia - must have evolved, and hence that they must have physical causes and physical effects in order to be subject to the principles of Darwinian evolution. The argument itself is credited to William James, and dates back to the 1870s, but Cairns-Smith suggests that coming to terms with the argument's consequences will require a significant shift in our understanding of cause and effect in the physical world.

The view presented is that good old-fashioned chemical brain states cause qualia, which cause (or at least influence) subsequent brain states. All this could be accomplished through standard chemical and biological means without imbuing qualia with any subjective qualities, but such an approach, Cairns-Smith argues, would not explain how or why qualia might have evolved. To give Cairns-Smith credit, he does push the standard chemical and biological approach to its limits before introducing qualia.

The result is a foray into neurophysiology yielding two rather astonishing claims: that monamine neurotransmitters are associated with qualia production and that there may be one neuropeptide for each possible sensation. It is at this point that one counter-intuitive and incomplete scientific theory (quantum theory) is wheeled in to "explain" the counter-intuitive and incompletely understood phenomenon of consciousness. Actually, there is no explanation. Quantum theory qualifies as the root of all qualia by default.

No alternatives are considered and no apologies are made. Although the focus of the book is qualia, the context for the discussion is provided by the equally thorny issue of free will. Do we have free will, or are our actions the result of some (non-deterministic) machine operating according to fixed principles (that may be discovered through scientific investigation)? The quantum account favours the latter. Our actions may not be fully deterministic (given the inherent probabilistic nature of quantum effects), but they are, on this account, describable by fixed principles.

Cairns-Smith is happy with this conclusion, but tempers it with an appeal to subjective experience: we do what we feel like doing, even if what we feel like doing results from scientifically investigable quantum effects. (So one functional role of qualia is clear - they make us feel good about being machines.) Perhaps it is unfair to tar all approaches to consciousness that appeal to quantum theory with one brush. It is curious though that, although the quantum story of consciousness has some eminent advocates (notably Sir Roger Penrose), few (if any) of those advocates are cognitive psychologists. Cairns-Smith might be right, qualia might result from quantum effects; but it is not a possibility I would bet my qualia on.

Richard Cooper is lecturer in psychology, Birkbeck College, London.