27 JUNE: THE GRAND ILLUSION
The Grand Illusion:
only exists when you look for it.
From New Scientist,
22 June 2002, p 26-29
The last great mystery
of science; the most baffling problem in the science of the mind; this
is how scientists talk about consciousness, but what if our conscious experience
is all a grand illusion?
Like most people, I used
to think of my conscious life as like a stream of experiences, passing
through my mind, one after another. But now Im starting to wonder, is
consciousness really like this? Could this apparently innocent assumption
be the reason we find consciousness so baffling?
Different strands of research
on the senses over the past decade suggest that the brave cognitive scientists,
psychologists and neuroscientists who dare to tackle the problem of consciousness
are chasing after the wrong thing. If consciousness seems to be a continuous
stream of rich and detailed sights, sounds, feelings and thoughts, then
I suggest this is the illusion.
First we must be clear what
is meant by the term illusion. To say that consciousness is an illusion
is not to say that it doesnt exist, but that it is not what it seems to
be?more like a mirage or a visual illusion. And if consciousness is not
what it seems, no wonder its proving such a mystery.
For the proposal Its all
an illusion even to be worth considering, the problem has to be serious.
And it is. We cant even begin to explain consciousness. Take this magazine
in front of your eyes. Right now, you are presumably having a conscious
experience of seeing the paper, the words, and the pictures. The way you
see the page is unique to you, and no one else can know exactly what it
is like for you. This is how consciousness is defined: it is your own subjective
But how do you get from a
magazine composed of atoms and molecules, to your experience of seeing
it? Real, physical objects and private experiences are such completely
different kinds of thing. How can one be related to the other? David Chalmers,
of the University of Tucson, Arizona, calls it the Hard Problem. How
can the firing of brain cells produce subjective experience? It seems like
magic; water into wine.
If you are not yet feeling
perplexed (in which case I am not doing my job properly), consider another
problem. It seems that most of what goes on in the brain is not conscious.
For example, we can consciously hear a song on the car radio, while we
are not necessarily conscious of all the things we do as were driving.
This leads us to make a fundamental distinction: contrasting conscious
brain processes with unconscious ones. But no one can explain what the
difference really is. Is there a special place in the brain where unconscious
things are made conscious? Are some brain cells endowed with an extra magic
something that makes what goes on in them subjective? This doesnt make
sense. Yet most theories of consciousness assume that there must be such
a difference, and then get stuck trying to explain or investigate it.
For example, in the currently
popular Global Workspace theory, Bernard Baars, of the Wright Institute
in Berkeley, California, equates the contents of consciousness with the
contents of working memory. But how does being in memory turn electrical
impulses into personal experiences?
Another popular line of research
is to search for the neural correlates of consciousness. Nobel Laureate,
Francis Crick, wants to pin down the brain activity that corresponds to
the vivid picture of the world we see in front of our eyes. And Oxford
pharmacologist, Susan Greenfield, is looking for the particular physical
state of the brain that always accompanies a subjective feeling (New Scientist,
2 Feb, p 30). These researchers are not alone in their search. But their
attempts all founder on exactly the same mystery?how can some kinds of
brain activity be in the conscious stream, while others are not? I cant
see what this difference could possibly be.
Could the problem be so serious
that we need to start again at the very beginning? Could it be that, after
all, there is no stream of consciousness; no movie in the brain; no picture
of the world we see in front of our eyes? Could all this be just a grand
You might want to protest.
You may be absolutely sure that you do have such a stream of conscious
experiences. But perhaps you have noticed this intriguing little oddity.
Imagine you are reading this magazine when suddenly you realise that the
clock is striking. You hadn’t noticed it before, but now that you have,
you know that the clock has struck four times already, and you can go on
counting. What is happening here? Were the first three dongs really unconscious
and have now been pulled out of memory and put in the stream of consciousness?
If so were the contents of the stream changed retrospectively to seem as
though you heard them at the time? Or what? You might think up some other
elaborations to make sense of it but they are unlikely to be either simple
A similar problem is apparent
with listening to speech. You need to hear several syllables before the
meaning of a sentence becomes unambiguous. So what was in the stream of
consciousness after one syllable? Did it switch from gobbledegook to words
half way through? It doesn’t feel like that. It feels as though you heard
a meaningful sentence as it went along. But that is impossible.
The running tap of time
Consciousness also does
funny things with time. A good example is the cutaneous rabbit. If a
persons arm is tapped rapidly, say five times at the wrist, then twice
near the elbow and finally three times on the upper arm, they report not
a series of separate taps coming in groups, but a continuous series moving
upwards?as though a little creature were running up their arm. We might
ask how taps two to four came to be experienced some way up the forearm
when the next tap in the series had not happened yet. How did the brain
know where the next tap was going to fall?
You might try to explain
it by saying that the stream of consciousness lags a little behind, just
in case more taps are coming. Or perhaps, when the elbow tap comes, the
brain runs back in time and changes the contents of consciousness. If so,
what was really in consciousness when the third tap happened? The problem
arises only if we think that things must always be either “in” or “out”
of consciousness. Perhaps, if this apparently natural distinction is causing
so much trouble, we should abandon it.
Even deeper troubles threaten
our sense of conscious vision. You might be utterly convinced that right
now you’re seeing a vivid and detailed picture of the world in front of
your eyes, and no one can tell you otherwise. Consider, then, a few experiments.
The most challenging are
studies of change blindness (New Scientist, 18 Nov 2000, p 28). Imagine
you are asked to look at the left hand picture in the illustration below.
Then at the exact moment you move your eyes (which you do several times
a second) the picture is swapped for the one on the right. Would you notice
the difference? Most people assume that they would. But they’d be wrong.
When our eyes are still we detect changes easily, but when a change happens
during an eye movement or a blink we are change blind.
Another way to reveal
change blindness is to present the two pictures one after the other repeatedly
on a computer screen with flashes of grey in between (for an example see
http://nivea.psycho.univ-paris5.fr/ASSChtml/kayakflick.gif). It can take
people many minutes to detect even a large object that changes colour,
or one that disappears altogether, even if its right in the middle of
What do these odd findings
mean? At the very least they challenge the textbook description that vision
is a process of building up representations in our heads of the world around
us. The idea is that as we move our eyes about, we build up an even better
picture, and this picture is what we consciously see. But these experiments
show that this way of thinking about vision has to be false. If we had
such a picture in our heads we would surely notice that something had changed,
yet we don’t. We jump to the conclusion that were seeing a continuous,
detailed and rich picture. But this is an illusion.
Researchers differ in how
far they think the illusion goes. Psychologists Daniel Simons of Harvard
University and Daniel Levin of Kent State University, Ohio, suggest that
during each visual fixation our brain builds a fleeting representation
of the scene. It then extracts the gist and throws away all the details.
This gives us the feeling of continuity and richness without too much overload.
Ronald Rensink of the University
of British Columbia in Vancouver, goes a little further and claims that
we never form representations of the whole scene at all, not even during
fixations. Instead we construct what he calls virtual representations
of just the object we are paying attention to. Nothing else is represented
in our heads, but we get the impression that everything is there because
a new object can always be made just in time whenever we look.
Finally, our ordinary notions
of seeing are more or less demolished by psychologists Kevin O’Regan of
the CNRS, the French national research agency in Paris, and Alva Noë
of the University of California, Santa Cruz, who first described vision
as a grand illusion. They argue that we don’t need internal representations
at all because the world is always there to be referred to. According to
their sensorimotor theory of vision seeing is not about building pictures
of the world in our heads, its about what you are doing. Seeing is a way
of interacting with the world, a kind of action. What remains between eye
movements is not a picture of the world but the information needed for
further exploration. The theory is dramatically different from existing
theories of perception.
Its not clear whos right.
Perhaps all these theories are off the mark, but there is no doubt about
the basic phenomenon and its main implication. Searching for the neural
correlates of the detailed, picture in our heads is doomed because there
is no such picture.
This leaves another problem.
If we have no picture, how can we act on the things we see? This question
may seem reasonable but it hides another false assumption?that we have
to see consciously in order to act. We need only think of the tennis player
who returns a serve before consciously seeing it, to realise that this
is false, but the situation is odder than this. We probably have several
separate visual systems that do their jobs somewhat independently, rather
than one single one that produces a unified visual world.
David Milner of the University
of St Andrews, and Melvyn Goodale of the University of Western Ontario,
argue that there is one system for fast visuomotor control and a slower
system for perceiving objects. Much of their evidence comes from patients
with brain damage, such as D.F. who has a condition known as visual form
agnosia. She cannot recognise objects by sight, name simple line drawings,
or recognise or copy letters, even though she produces letters correctly
from dictation and can recognise objects by touch. She can also reach out
and grasp everyday objects (objects that she cannot recognise) with remarkable
accuracy. D.F. seems to have a visual system that guides her actions but
her perception system is damaged.
In a revealing experiment
D.F. was shown a slot set randomly at different angles. (Trends in Neurosciences,
vol 15 p 20, 1992). She could not consciously see the orientation of the
slot, and could not draw it or adjust a line to the same angle. But when
given a piece of card she could quickly and accurately line it up and post
it straight through. Experiments with normal volunteers have shown similar
kinds of dissociation, suggesting that we all have at least two separate
Perhaps the most obvious
conclusion is that the slow perceptual system is conscious and the fast
action system is unconscious. But then the old mystery is back. We would
have to explain the difference between conscious and unconscious systems.
Is there a magic ingredient in one? Does neural information turn into subjective
experiences just because it is processed more slowly?
Perhaps the answer here is
to admit that there is no stream of conscious experiences on which we act.
Instead, at any time a whole lot of different things are going on in our
brain at once. None of these things is either in or out of consciousness
but every so often, something happens to create what seems to have been
a unified conscious stream; an illusion of richness and continuity.
It sounds bizarre, but try
to catch yourself not being conscious. More than a hundred years ago the
psychologist William James likened introspective analysis to trying to
turn up the gas quickly enough to see how the darkness looks.” The modern
equivalent is looking in the fridge to see whether the light is always
on. However quickly you open the door, you can never catch it out. The
same is true of consciousness. Whenever you ask yourself, Am I conscious
now? you always are.
But perhaps there is only
something there when you ask. Maybe each time you probe, a retrospective
story is concocted about what was in the stream of consciousness a moment
before, together with a self who was apparently experiencing it. Of course
there was neither a conscious self nor a stream, but it now seems as though
Perhaps a new story is concocted
whenever you bother to look. When we ask ourselves about it, it would seem
as though theres a stream of consciousness going on. When we don’t bother
to ask, or to look, it doesn’t, but then we don’t notice so it doesn’t
Admitting that its
all an illusion does not solve the problem of consciousness but changes
it completely. Instead of asking how neural impulses turn into conscious
experiences, we must ask how the grand illusion gets constructed. This
will prove no easy task, but unlike solving the Hard Problem it may at
least be possible.
Susan Blackmore is a psychologist,
writer and lecturer based in Bristol.
by Daniel Dennett, Penguin (1993)
ORegan and Noës ideas
will soon be debated in a special issue of Behavioral and Brain Sciences.
N.B. The current issue of
Journal of Consciousness Studies is devoted to the Grand Illusion.
This will also be published
as a book Is the Visual World a Grand Illusion? Ed. Alva Noë, Imprint