One theory of consciousness rules supreme, Tony Durham reports, while readers reply to one scientist's views.

Judging by the 100 or so responses to our questionnaire on consciousness, THES readers are optimistic that a solution will be found to the problem of how physical processes in the brain give rise to our awareness of everything - colours, smells, fears, memories . . . In the field this has become known as the "hard problem" of consciousness. Two-thirds of respondents to the questionnaire (THES, April 5) believe the "hard problem" is soluble, and over a quarter are convinced it will be solved.

Where will the crucial insights come from? Readers rejected brash claims that neuroscience has all the answers. Among the many competing theories on offer, they picked a clear leader that won more than twice the votes of its closest rival.

The scientific instinct has always been to reduce every phenomenon to its simplest components, be they physical or neurophysiological. But in a resounding rejection of reductionism, 40 per cent of respondents subscribed to what might be called the "emergent" theory, popularised in Alwyn Scott's book, Stairway to the Mind. In this view, each hierarchical level from physics upwards adds something unique to make consciousness possible. Consciousness is not susceptible to simple explanations based on any single branch of science.

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Question one asked you to imagine the quality of consciousness of various creatures from snail to fellow-human, and hypothetical entities including zombies and brain-silicon hybrids. The replies revealed a degree of "carbon chauvinism", with more granting consciousness to the snail (68 per cent) than to a super-intelligent computer (41 per cent). Unconvinced by countless science-fiction tales, 51 per cent thought an extremely intelligent computer would lack consciousness while a further 7 per cent thought the question did not arise since no such machine could be built. Only 5 per cent believed computer consciousness would be similar to their own. The consensus was that if machine awareness is possible, it will be distinctly alien.

The question on whether "your brain program copied to silicon" would be conscious produced a variety of responses. A third dismissed the experiment as impossible. Of those prepared to speculate, the weight of opinion was that the "brain program" would be conscious.

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Among mammals, the bat was held by 85 per cent to be conscious while only three respondents denied consciousness to the chimpanzee. Sixteen per cent thought a chimpanzee's conscious experience was similar to their own, but most thought it was different in intensity, in quality or both.

Most swallowed their solipsistic doubts and judged one human's conscious experience is similar to another's. But 21 per cent believed it might differ in quality or intensity. The issue of intensity is somehow disturbing. All humans are conscious, but some are more conscious than others?

Most people were broadminded in choosing sources of evidence about consciousness. Of the 11 branches of inquiry named, the average reply judged no fewer than eight to be useful or essential. Parapsychology was the least trusted ("likely to mislead" for 40 per cent) while 64 per cent considered neuroscience to be essential.

Roger Penrose and Stuart Hameroff appear to have won few converts for their view that consciousness is a quantum-mechanical phenomenon. Interestingly, traditional mind/matter dualists outnumbered the modern software/hardware dualists who regard mind as a program that could run on a brain or any other sufficiently powerful computer. But neither was a popular position. There was more support for the idea that some new, fundamental principle is involved in consciousness.

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Neuroscience has been a rich source of new information, justifying the claim that a new science of consciousness is emerging. Yet relatively few thought neuroscience could by itself produce a plausible theory of consciousness. There was stronger support for the kind of theory that "it's something about the whole body and the world it inhabits", but the multi-disciplinary "emergent" theory was the overwhelming winner.

Perhaps this should be no surprise. The message is that the science of consciousness is intrinsically multidisciplinary. But it is an uncomfortable message for those like Crick (THES, May 24) who think the subject should only concern neuroscientists, a few psychologists and a philosopher or two.

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