Under the Microscope: How does science explain consciousness? In two words, it doesn't.
In 1989 Stuart Sutherland declared in The International Dictionary Of Psychology: "Consciousness is a fascinating but elusive phenomenon; it is impossible to specify what it is, what it does or why it evolved. Nothing worth reading has been written on it." Although the situation is not so bleak today, science still has an enormous distance to travel to explain consciousness.
The conscious human mind records and expresses our subjective experiences and gives each of us a unique inner life. The human brain and associated conscious mind are the most complex things we know of. A few scientists believe that understanding how the mind works is beyond the capacity of the human brain; others believe such an understanding will require a revolution in physics.
Most, however, believe that working with patients will eventually allow neurobiochemists, neurophysiologists and neuroanatomists to elucidate the mechanism of the consciousness-mind-brain connection: so many things that once seemed mysterious were explained by the gradual but relentless progress of chemistry, biology and physics.
Many scientists believe self-conscious thinking is simply what the brain does. More specifically, they categorise thinking as an emergent property - that is, one that arises unexpectedly when matter organises itself in certain ways.
An emergent property cannot be predicted in advance based on the properties of the material subcomponents, although of course in hindsight the emergent property is seen to be fully reconcilable with the properties of the material subcomponents.
So the properties of liquid water are an emergent property that arise when countless numbers of H2O molecules come together at moderate temperature and pressure.
Likewise, the properties of solid ice are emergent when water molecules come together at low temperature. Just as the wetness of liquid water would never be predicted from the properties of an individual water molecule, so many scientists believe consciousness is simply an emergent property of the very complex arrangement of matter in the brain.
The physicist and Anglican theologian John Polkinghorne finds this analogy unconvincing. Solidity and fluidity are energetic properties of matter in the aggregate, and it is not surprising that they emerge from energetic transactions between constituent molecules. Mental events do not have the character of energetic processes.
In a general sense, like can only explain like. Energetic properties are explained by energetic interactions. Mental properties would seem to require more than that, because they are incommensurable with the merely material.
I am not hinting that the thinking-conscious process does not depend on the brain - clearly it does. The relationship between the two may well be different to anything science has encountered, however. A detailed understanding of the biochemistry, physiology and structure of the brain may well tell us little more about conscious thinking than a study of the foundation of a house could tell about the purposes for which its rooms might be used. The structure and use of the house are dependent on the foundation, but they are not entailed by that foundation.
Psychologists are also busily studying the nature of consciousness; some of the results are not only fascinating but also indicate how far we have to travel before we will understand the process.
Consider blind sight. Damage to a part of the visual cortex on one side of the brain causes a blind patch on the opposite side of the visual field. Patients with this damage consciously see nothing in this area. A light can be flashed in this blind area, for example, and the patient will insist he sees nothing. Yet experiments have shown that the patient can nevertheless point to the location of the flashed light. Blind sight is counter-intuitive. How can people respond to something they cannot see? Doesn't consciousness have to precede action?
Again, hold your arm straight out in front of you. Then, of your own free will, flex your wrist. Repeat the action several times. It seems clear that you first consciously decide to move your wrist, then it moves. This was carefully investigated in the mid-1980s. People were asked to do this wrist-bending exercise while three things were timed: the beginning of the action, using electrodes on the wrist; the beginning of readiness activity in the brain, using electrodes on the scalp; and the time of the conscious decision to move. The results were dramatic. Brain activity began about half a second before the person was conscious of deciding to act. In other words, the conscious decision came too late to be the cause of the action.
Consciousness is the last and the most important frontier in biology. Science is only nibbling at the edge of this vast territory. At the moment, perhaps all that could be agreed by those who study it is an in-joke definition - consciousness: that annoying time between naps.
If you are interested in finding out more you could delve into an article by Susan Blackmore in the October 2001 edition of the Psychologist. William Reville is associate professor of biochemistry and director of microscopy at University College Cork