Times Higher
Education Supplement, 30 September 2005, 28-9
Review of
The world in my mind, my mind in the
world by Igor Aleksander, Exeter, Imprint Academic,
196 pp, £17.95 hbk ISBN 1 84540 021 6, published 17 May 2005, and
Consciousness:
creeping up on the hard problem by Jeffrey Gray, Oxford,
Oxford University Press, 341 pp, hbk ISBN 0 19 852090 5 £29.95
published 17 June 2004
(This is the version submitted. It
may have been edited before publication.)
These two books - both on the hard problem of
consciousness – could hardly be more different. Igor Aleksander, an
engineer whose ideas are inspired by building robots, wonders what is
required to make them conscious. Jeffrey Gray, a well-known
psychologist who died last year, amassed a vast amount of evidence
from neuroscience, philosophy and psychology to construct his own
solution to what some people believe is the last remaining mystery for
science.
Both begin by outlining the “hard problem”, a
phrase coined by philosopher Dave Chalmers. The problem is to
understand how subjective experiences, or “what it’s like to
be”, can arise from the activity of physical brain cells; or, to put
it a different way, to explain how the redness of red or the ineffable
smell of lavender (those qualities that philosophers call
“qualia”) can be created by the brain. This really does seem to be
a mystery because brains and private feelings appear to be utterly
different kinds of thing – so how can one explain the other?
Amidst all the confusion there are two major
responses to the mystery. On one side the “nothing extra” camp
believes that once all the structures and functions of the brain have
been explained there will be no mystery left over – as happened with
“phlogiston” or the once mysterious “life force”. In other
words, there is no such thing as “consciousness itself” and the
task is to reduce consciousness to something else. Some versions
equate consciousness with the functions the brain carries out. Some
claim that consciousness simply is brain activity. The trouble is that
so far no one has explained how this can be so.
Closer to everyday intuitions is the “something
extra” side, who believe that consciousness is, as it seems to be,
something additional to other brain functions, with its own powers,
properties and functions. Here the task is to understand how something
so peculiar and indefinable can possibly be produced by the brain or
correlated with brain activity. In this view consciousness really is
mysterious, and the hard problem is really hard.
Aleksander puts himself firmly in the
reductionist “nothing extra” camp by saying that mechanism and
sensation are as inseparable as H2O and water – they are identical.
So he is not looking for the neural correlates of consciousness but
for the “Neural IDENTITY of Being Conscious”. Conscious sensations
are neural activity, he says, because believing anything else would be
tantamount to believing in ghosts. He proposes five axioms that derive
from his own first-person, conscious experience, including the feeling
of experiencing an outside world, having memories, selective
attention, planning, and emotions. He then sets about explaining how
these can be applied both to artificial systems such as robots and to
living ones such as ourselves.
The critical function, according to Aleksander,
is the process he calls “depiction”, a kind of very rich,
multimodal representation of the world whose contents become what we
are conscious of. However, Aleksander never explains what is meant by
this identity, nor why the contents of such depictions end up as
subjective experiences when the contents of other kinds of
representation do not.
Some people, myself included, have argued that
consciousness is an illusion. Aleksander rejects this idea but gets
into a fearful muddle in the process. He seems to confuse the idea of
visual illusions, when we make mistakes about what is out there in the
world, with what is known as “Grand Illusion” theory when we make
mistakes about the nature of our own experience, for example, wrongly
believing that we experience a stream of rich and detailed
representations of the world when in fact we have only fleeting scraps
of perception and an illusion of richness and continuity.
Aleksander’s most important contribution is in
considering how a machine could be conscious and what would make it
so, but in the end I was not convinced by his claim that the process
of depiction holds the key. Although he claims that mechanism and
conscious experiences are the same thing, he still lapses into saying
that the brain “generates” or “supports” consciousness as
though consciousness were, after all, a mysterious added extra.
Jeffrey Grey, by contrast, does not shrink from
tackling the mystery head on. Indeed he fully embraces the idea that
the brain generates qualia, and tries to explain how. For example,
there is the difficult question of what consciousness is for and why
it evolved. If you think that brain activity and subjective
experiences are the same thing (or that functions such as perception
and memory are) then you have no problem with evolution because
natural selection favours those functions and abilities, and you do
not have to explain consciousness as well. But if, like Gray, you
think that consciousness is an added extra then you have to explain
what it is for.
According to Gray, qualia are indeed added
extras. He even suggests, I think uniquely among consciousness
theorists, that the pairings between meanings and qualia are
potentially flexible – that evolution might have attached different
qualia to different functions, or none at all. So there must be a
reason why they are linked up the way they are. He claims that qualia,
once created, can be put to the service of a great variety of
cognitive processes. So they have very important functions that are
quite separate from the functions of the brain processes that create
them.
The function of qualia cannot be the fast on-line
control of behaviours, even though it may feel that way. Gray explains
why not using both everyday examples – such as the tennis player who
hits the ball back long before she can have consciously seen it coming
– and detailed descriptions of many fascinating experiments. It is
precisely such experimental findings that have led many theorists to
treat consciousness as an illusion, or as nothing but the functions of
the brain, or even as an epiphenomenon, but not Gray. Instead he
suggests that consciousness acts as a late error detection mechanism.
The human cognitive system relies on a comparator system that, in
discrete moments of about a tenth of a second, makes plans, generates
predictions about what will happen next, and compares them with
sensory perceptions. All this is done unconsciously but then the
outputs of the comparator, the mismatches, finally “enter
consciousness”. Once “in consciousness” the slow time-scale
there ensures that we experience a smooth and stable constructed
world, and errors can be detected for improving future actions.
Gray’s is an unusual and daring theory but I
don’t think it works because it leaves the central mystery intact.
What does it mean to say that something “enters consciousness”? Is
consciousness some kind of place in the brain or mind? Or, if not,
what happens to neural activity to make it turn into, or create, or
generate, qualia? I don’t believe the theory provides answers.
Nevertheless this is a superb book. Gray’s descriptions of the
experiments are clear and accurate, his explanations of the competing
theories are lucid and helpful, and his own theory is an interesting
challenge to all of us still tearing our hair out over the mysteries
of consciousness. Everyone working in consciousness studies should
read it.
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