Right up there with the Big Bang and a reconciliation of quantum theory with Newtonian physics, biology has a daunting challenge all of its own, arguably the most difficult question ever: where is the physical basis for the subjective, first-hand experience of what we call consciousness?
Over recent decades, this slippery concept, so intractable to the objective machinery of scientific method, has nonetheless become respectable among a growing number of scientists, if not, sadly, with the institutions that fund their research.
There’s a good reason this biological problem perhaps outstrips even the most fundamental question in the physical sciences: we have no idea of what kind of answer to expect. What exactly are we expecting as a “solution” to the puzzle of how the brain generates consciousness?
A performing rat, a pretty brain scan, a cabbalistic formula, you-suddenly-feeling- as-though-you’re-me, or is it that clichéd answer, the conscious computer?
We can go either from biology to IT or follow the reverse route. If we start with the biological phenomenon of consciousness, something so familiar and undeniable, yet indefinable, then the usual idea is that we model the phenomenon in an artificial system. But hang on just a minute. The idea of a model is that you focus on the salient features and jettison the extraneous ones. A model for flight, as exemplified by an aeroplane, would simply be the defying of gravity. We can leave out the feathers and the beak.
So, if we’re to model consciousness, then we would have to know what the salient physical brain/body process(es) was/were, and what bits of the brain and body we could ignore. The thing is, if we knew that, then we would have already solved the problem and there would be no need to bother with a model at all.
The value of travelling in the reverse direction, starting with an artificial system to elucidate the biology, cannot be so quickly dismissed. A distinguished and diverse line-up of scientists such as Ray Kurzweil, Giulio Tononi and Christof Koch, as well as the now-defunct Cog and the more recent Leonardo projects at MIT, all share the idea that it might, in the end, be size that counts and that complexity, whether it is found in neuronal networks, or, as the philosopher John Searle once sagely remarked, old beer cans, was all that counted for consciousness to emerge.
This way of thinking, frankly, offends my sensibilities as a neurochemist, concerned as I am with the trafficking of the huge variety of capricious and subtle compounds in the nervous system that work in different combinations, in different places, over different windows of time, with highly contextdependent and variable effects.
Moreover, we shouldn’t forget what’s happening below the eyebrows. The brain, obviously, doesn’t work in isolation and there is incessant feedback to and from the brain and the body it inhabits. How do we know that the interplay between the great control systems – the immune, endocrine and nervous systems – might not be a necessary prerequisite? For me, quality cannot be reduced to quantity, to mere computation.
And yet, and yet… Just imagine a robot or computer that was truly self-aware. What stories it might be able to tell! Well, maybe. But how would such a garrulous marvel help us understand consciousness, be it emerging from a silicon or carbon mechanism?
Let’s leave aside the fascinating issue of how similar biological and synthetic consciousness need to be in order to be regarded as the same phenomenon. I still struggle to see how an artificial system that passed the Turing test (whereby an impartial observer could not distinguish between the responses of a human versus a machine) would help solve the “hard problem”: how the subjective “feel” of consciousness is generated in an objective, physical system.
In any case, at the moment it’s all hypothetical. The Turing test has still not been passed, although there is apparently a human being somewhere who failed it. Whatever their reasons for doing it, perhaps for those fixated on building a conscious machine of some sort, the most exciting strategy would be to strive to satisfy the late Stuart Sutherland’s criterion, that he would accept that a computer was conscious only when it ran off with his wife.
Susan Greenfield’s research is focused on brain physiology and she has written several popular-science books about the brain and consciousness. She was created a life peer in 2001 and is director of the Royal Institution.