Despite the immediacy of qualia,
it must be remembered that they result from at least one translation: that of
a physical stimulus into action
potential frequencies. For example, for an electromagnetic wave with
a wavelength of 700 nm to acquire the qualium “red”, it must first
be transduced by the photoreceptor
cells in the retina. And it is the series of action potentials along
particular pathways leading to the visual cortex that is the proximal cause, as
it were, of the qualium.
Some authors even speak of
a second translation in which these encoded impulses are converted into qualia.
But that position is already controversial, because it is based on a certain
philosophical conception of qualia.
philosophical presupposition, a
materialist one in this case, establishes an equivalence between
a qualium and a particular physiochemical state in the brain, somewhat the same
way that heat corresponds to molecular kinetic energy or that visible light corresponds
to certain radiant electromagnetic energy.
such as the philosopher Daniel
Dennett, even try to convince us that in the end, what we call qualia
do not actually exist. Because while it is hard to deny the existence of something
very general such as “subjective experience”, the term “qualia”,
being more precise and coming from the jargon of philosophers, is more vulnerable
Block, half-jokingly defines qualia by borrowing the definition
of jazz that is attributed to Louis Armstrong: “If you got to ask, you ain’t
never gonna get to know.” But that leaves philosophers like Dennett unsatisfied.
Dennett is convinced, for example, that some time in future, the concept of qualia
will have no more value than the concept of élan vital (“vital
impetus”, or “vital force”), which was highly popular before
the molecular mechanisms of life were understood but has now fallen into disuse.
WHAT IS CONSCIOUSNESS?
For many reasons, human
consciousness is very hard to define. In particular, the kind of problem that
it poses for science is very different from that of explaining physical phenomena
such as falling objects, photosynthesis, or nuclear fusion. This difference has
been characterized in various ways, with a number of different dichotomies.
For example, some authors have stressed the private
nature of consciousness, which is accessible only from the viewpoint of
the conscious subject, whereas physical phenomena are accessible to any
Others have stressed the ineffability
of consciousness: it cannot be effectively explained in terms of language, unlike
physical phenomena, whose properties can be accurately expressed in terms such
as mass or temperature.
In a 1974 article
entitled “What is it Like to Be a Bat?”, the philosopher Thomas
Nagel focused on these subjective properties of conscious human experience.
To do so, he tried to imagine the subjective
viewpoint of an animal with a sensory spectrum very different from our own: a
bat. Bats orient themselves in space by echolocation: they emit high-frequency
shrieks, then use the echoes returned by obstacles or prey to locate them.
was to show that because humans are incapable of echolocation, they will never
be able to subjectively feel “what it is like” to orient themselves
in this way. Just as we humans, with our sense of sight, perceive not electromagnetic
waves in the visible-light spectrum, but rather illuminated objects, bats may
perceive their returning echoes not as sounds, but directly as objects. That,
however, is something we will never know.
is exactly what is meant by the subjective side of conscious experience, compared
with its objective side. In the bat’s case, the objective side is the acoustical
physics of echolocation, which we can describe and understand, unlike its subjective
side, which we cannot. Nagel therefore concludes that science has taught us many
things about how a bat’s brain functions, but not “what it is like”
to be a bat.
This subjective aspect of “what
it is like” to have any given conscious state is also referred to as the
phenomenologicalaspect of consciousness. A
related term, qualia (the plural of qualium or quale), more specifically
designates all of our direct impressions of things. Qualia are the immediate experiential
aspects of sensations—to offer some crude examples, the particular redness
of the red of an apple, or the coldness of ice. Some authors even extend the concept
of qualia to our most basic thoughts and drives.
literature is brimming with “thought experiments” attempting to grasp
the essence of qualia. One of the most famous of these experiments was proposed
by philosopher Frank Jackson in 1982. Imagine that Marie is one
of the world’s greatest neurobiologists in the field of colour
vision, but that she has lived her entire life enclosed in a room where
everything is black and white. Everything that she knows about colour vision,
she has learned from the books, printed in black ink on white pages, that she
has been reading since she was a little girl. Thus Marie has come to know all
of the relevant facts about how humans perceive colours.
suppose that one day, for the first time in her life, Marie leaves her room and
sees the real colours of the world around her. She sees some red tulips and exclaims,
“This is what it’s like to see red!”. As Jackson tells us in
his thought experiment, at this point Marie appears to be experiencing something
completely new. So how it is possible that even though she has had access to absolutely
every imaginable piece of information about colour vision, she is now discovering
something new by simply seeing a colour? This something new, Jackson’s fable
concludes, is the qualium of the particular red of the particular flowers that
she has seen.
In other words, even
an extremely accurate knowledge of the brain and of the neural
correlates of subjective consciousness does not appear to give access
to the experience itself: what the subject is experiencing as a subject.
thought experiment naturally became the target of much commentary and criticism,
particularly by thinkers who championed a materialist
approach to consciousness. At the time that he published his thought
experiment, Jackson himself regarded consciousness as an epiphenomenon.
But he later came to reject this idea, because if Marie exclaimed when she saw
colour for the first time, then this qualium was what caused her exclamation.
Since epiphenomenalism does not accept that qualia can affect the physiology of
the brain, and since Jackson was convinced that only physical causes can influence
the physical world, there was a serious problem in accepting his original metaphor
It would be chauvinistic to make
an a priori assertion that only humans can be conscious. For a theory
of consciousness to be as general as possible, it must therefore also account
for the possibility of non-human consciousness (for example, in animals or machines).
Some authors believe that the concept of
intentionality, a sophisticated way of talking about mental representations,
might facilitate the development of a general theory of consciousness. Toward
the end of the 19th century, the German philosopher Franz Brentano (1838-1917)
developed the idea that the essence of mental activity is to be object-directed.
For Brentano, all consciousness is consciousness of something.
this sense, language is intentional. For example, if you think of the word “Montreal”,
you may imagine the sight of Mount Royal overlooking that city, or perhaps the
Olympic Stadium with its famous mast. But how does our understanding of the thing
that is signified by a word enable us to form a mental representation of that
thing? This is the kind of problem raised by the concept of intentionality, and
it is just as hard to solve as the “hard
problem” of consciousness.
The biological research done during
the 20th century discredited the notion of the existence of mental forces with
properties distinct from physical forces. Over the course of this century, researchers
compiled an impressive volume of data on the neural circuits of the brain and
how they function, but never uncovered any sign of the presence of separate mental
Some eminent 20th-century neurobiologists,
such as John
Eccles and Roger Sperry, defended the idea that the conscious mind
was separate from the brain and could sometimes exert an independent influence
on its operations. But now, in the early 21st century, most neurobiologists reject
the idea of mental causes separate from the physical world.
PHILOSOPHICAL POSITIONS ON CONSCIOUSNESS
How can we explain
the subjectivity of human consciousness, or, to use Thomas Nagel’s phrase,
“what it is like” to be
ourselves. Or, as David Chalmers would put it, how do we solve the
“hard problem” of consciousness?
to substance dualism, the material world does in fact exist,
but the subjective aspects of consciousness are of a different nature and constitute
the other great substance of which the world is made. This immediately raises
the question of the interaction between this subjective world and the physical
one—a very difficult question to which the philosopher René Descartes,
who distinguished the res extensa (material substance) from the res
cogitans (thinking substance), provided an
explanation that has been refuted since.
Even so, substance dualism
has had a hard time. As early as the 4th century B.C.E., Plato distinguished a
mortal body from an immortal soul. In a later age, this thesis served Christian
theologians’ purposes so well that they unabashedly backed it with all the
authority that the political
power of the Church conferred on them for many centuries.
subsequently, substance dualism has been shaken to its very foundations by questions
about what its detractors such as philosopher Gilbert Ryle have called the myth
of the “ghost in the machine”. For example, if the human body is a
physical machine piloted by a non-physical ghost hiding somewhere inside the human
skull, where exactly is that ghost hiding? And is there only one such ghost, or
are there many? Who animates the ghost itself, and through what force does this
ghost affect the physical world?
In an attempt to
retain the advantages of having two separate entities, but avoid the pitfalls
of substance dualism, philosophers have developed several
variants of dualism. These include:
dualism, which accepts that humans are composed only of matter, but that
this matter has two very distinct types of properties;
which recognizes the causal effects of the brain on the mind, but not of the mind
on the brain; and
which holds that mental states are more than the sum of their material parts but
can nevertheless interact with them.
other major school of philosophy that has has something to say about consciousness
is materialism. For materialists, the causal
relationship between our mental states and our behaviours does not pose any
problem, because both are part of the physical world. A subjective experience
such as pain is quite real, but simply consists of the neuronal states that give
rise to it.
This materialist framework
is monistic: it holds that only matter exists. But within it, there have been
two main interpretations about the nature of
The first, known as dual-aspect monism or neutral
monism, has been championed by thinkers such as Baruch Spinoza, George
Henry Lewes, Thomas Nagel, and Mark
Solms. It states that matter is a single substance, but can be perceived from
two different perspectives. Just as a curve remains a line even though it can
be described as concave or convex at any given time, so our psychophysical processes
remain the same regardless of whether we are talking about them from a physical
standpoint or a mental one.
for the proponents of the dual-aspect theory, your brain can appear to you as
something physical when you regard it as an object from the outside, but as something
“mental” when you, as a subject, examine it from the inside (by introspection).
Just as physicists can speak of light as a wave and a particle simultaneously,
we can regard the body and the mind as simply the two sides of the same coin.
The age-old distinction between mind and body may therefore have been nothing
more than an artifact of perception.
a movement that tries to combine data from the neurosciences and psychoanalysis
to achieve a better understanding of human consciousness, is based on dual-aspect
The second main materialist interpretation
of the nature of the mind is psychophysical identity theory.
This theory postulates that there is an identity between a person’s conscious
states and the physical states of his or her brain. In psychophysical identity
theory, unlike in dual-aspect theory, the subjective and objective natures of
consciousness cannot be regarded as two different aspects of the same thing, because
they are one and the same thing. In other words, mental states can be completely
reduced to physical ones, just as water can be reduced to its chemical formula
The problem then, of course, is to
explain how the objective and the subjective, the brain and the mind, can be identical
when they seem so different. Two different forms of identity, “type
to type” identity and “token to token” identity, have been
proposed. They lead to two variants of reductive materialism, one based on identity
in the stronger sense and the other on identity in the weaker sense.
materialism is even more radical than the two forms of materialism
just discussed. Like materialist
functionalism, eliminative materialism seeks to circumvent
the difficulties inherent in materialism while accepting its basic premise: that
matter is the only thing that exists.
Lastly, the mysterian
school of philosophers, whose best known representative is Colin McGinn,
are non-materialists who think that the problem of human consciousness simply
surpasses human understanding. They refuse to believe that our subjective vision
of colours, for example, is simply identical to the activity of a population of
neurons in certain areas of the cortex.
At the same
time, however, these philosophers do not want to return to dualism. They therefore
argue that consciousness is a mystery, and that it is a mystery because our concepts
of the mental and physical world are too crude to address the problem of the relationship
between the body and the mind in an enlightening way. It is somewhat the same
as the reason that monkeys will never perform differential calculus: it would
require concepts that are inaccessible to their brains. In fact, every species
has limits to its cognitive abilities, and understanding consciousness may just
require some concepts that humans simply cannot access.
the materialists say that the mysterians have given up too fast and that they
base their conclusion on nothing more than their disbelief in the possibility
that the brain’s grey matter can constitute the world in the bright colours
that we experience every day. Some materialists believe that one way to make the
identity between consciousness and matter less counterintuitive is to apply new
concepts from the cognitive
neurosciences to our thinking about the phenomenological
aspect of consciousness.
The English mathematician Alan
Turing (1912-1954) believed that in the relatively near future, scientists
would manage to program a computer so as to give it conscious states. To determine
when that goal would have been reached, he developed what is now known as the
Turing Test. This test assumes that one is in communication with
an entity that one cannot see, through some remote mechanism such as postal mail
or e-mail. The task is to ask this entity questions so as to determine whether
it is a human or a computer. If the entity is a machine, and it succeeds in fooling
you into thinking that it is human, then it has passed the Turing Test and it
can be assumed to have the same conscious states as a human being.
a number of critics have objected that a computer that passes the Turing Test
might simply be simulating conscious states in a very sophisticated way.
The idea that the
essence of human thought is similar to the operation of computers—that it
consists of symbolic representations manipulated by logical operations—continues
to influence the cognitive sciences, even though this view is less common now
than in the 1960s or 1970s.
attempt to understand
the operation of human consciousness directly, by analyzing its various components,
artificial intelligence (AI) researchers attempt to build machines
that resemble the human mind as closely as possible. These researchers hope that
if they can succeed in building a machine whose responses can be mistaken for
those of a human mind (see preceding sidebar), then we may learn what a system
must contain in order for a consciousness to emerge from it.
would this be a truly “human” consciousness in the sense that we experience
it, or would it be a different form of consciousness, specific to this particular
kind of machine? Or would it be only a simulation of consciousness, as some skeptics
and the proponents of “weak AI” would have it (see the discussion
to the right)? Or perhaps the Dutch computer scientist Edsger Dijkstra
had it right when he said: “The question of whether a computer can think
is no more interesting than the question of whether a submarine can swim.”
CONSCIOUSNESS IN THE COGNITIVE SCIENCES
From 1946 to 1953,
field of psychology was still dominated by behaviourism, the Macy Foundation
sponsored a series of conferences in New York City and at Princeton University,
in New Jersey. These conferences were attended by specialists from many disciplines,
ranging from mathematics to psychology to anthropology, sociology, and neurobiology.
The scholars such as Wiener,
Shannon, McCulloch, von Foerster, and von
Neumann who regularly attended these conferences strongly advocated that they
take a multidisciplinary approach, which proved highly productive. What are now
known as the Macy Conferences gave rise to the cybernetics movement.
Now defined as the general science of communication and control in natural and
artificial systems, cybernetics studies how information circulates.
A number of ideas that originated in
cybernetics have gone on to profoundly influence all fields of science (biology,
economics, ecology, and so on—follow the Tool Module link to the left).
For example, the concept of feedback has led to a better understanding of the
ways in which hormones control the human body.
Many biologists, such as Henri
Laborit and Henri
Atlan, were greatly influenced by concepts of cybernetics. This new science
also quickly found applications in computing, then in its infancy, as well as
in what would later become known as artificial intelligence (see sidebar).
cyberneticists were also clearly interested in investigating the complex system
par excellence: the human mind. And because they rejected
all forms of idealism and shared a strong inclination toward materialism,
they quite naturally included the study of the brain in their two approaches to
the “top-down” approach
(decomposition or reduction);
approach (global or systemic construction, or synthesis).
two approaches tended to complement rather than contradict one another. They gave
rise to the two main currents that developed subsequently in the cognitive sciences:
cognitivism and connectionism, respectively.
developed during World War II, though still very slow, were a great source of
inspiration for the cognitivist (also known as the computational)
approach. The classic use of the computer as a metaphor for the human mind (though
we now know its limitations—follow the Tool Module link to the left) thus
led the cognitivists to believe that the mind translates the components of the
external world into internal representations, exactly as a computer does.
to the cognitivists, the mind then manipulates these internal symbolic representations
according to certain predetermined rules so as to provide appropriate responses,
or “outputs”. In other words, the cognitivists saw thought as a form
of information processing.
of cognitivism dominated the cognitive sciences from the mid-1950s for almost
20 years. As Jerry Fodor, a student of Hilary Putnam,
couched the argument, to think is to manipulate symbols,
and cognition is nothing more than manipulating symbols the way that computers
do. This premise and Fodor’s research inspired the various functionalist
approaches, according to which the mind is organized into specialized modules
that can be implemented on platforms other than computers. This is the famous
concept of “multiple realization”.
mental states had been equated with computer software and the brain with computer
hardware, computer simulation and modelling became an ideal means of studying
how the human mind operates. This field of inquiry came to be known as “artificial
intelligence”, or AI (see sidebar).
John Searle distinguished two positions regarding the possibilities
of AI. According to the “strong AI” position, to
be intelligent, all a machine needed was the right program. But Searle dealt this
position a harsh blow with his Chinese
According to the “weak
AI” position, computers can only simulate the human mind. No matter
how much computational power they have, they can never create a true intelligence
or a genuine consciousness. Meteorologists’ computers, though they may be
able to simulate the development of hurricanes with great accuracy, are never
going to soak us to the skin or flatten our homes.
inspired by the operation of computers that manipulate symbols without interpreting
their meaning, is forced to reduce the brain to a simple syntactic device, and
not a semantic one. Epistemologically speaking, this position is vulnerable
to attack from many angles.
It was in this context
that connectionism, the other major current in the cognitive
sciences, developed in the 1980s.
The roots of connectionism lie in cybernetics and
neurobiology, and accordingly, its primary analogy for the human mind is a network
of numerous interconnected units. This new approach, based on networks of artificial
neurons that process information in parallel, was developed to make the structure
of cognitive models more closely approximate that of the brain.
Thus connectionism is a “bottom-up”
approach. It is associated with philosophers such as Daniel
Dennett and Douglas Hofstadter. In connectionism, mental representations
are not discussed in terms of symbols, but instead are analyzed in terms of links
among numerous distributed, co-operative, self-organizing agents.
Minsky, who inspired this approach, thus regards the cognitive system
as a society of micro-agents that are capable of solving problems locally. Connectionists
therefore believe that the analysis must penetrate down inside symbolic operations,
to the “sub-symbolic” level.
to the computing analogy used in cognitivism, connectionism does not depend on
complex algorithms that are executed sequentially, or on a control centre that
processes all the information, because the networks of neurons in the brain are
considered quite capable of doing without them. What is special about the brain’s
neural networks, however, besides their distributed mode of operation, is that
of the connections among them is altered by experience.
was thus inspired directly by Hebb’s
rule, which states that when two neurons tend to be activated simultaneously,
their connections are strengthened; when the opposite is true, then their connections
become weaker. The connectivity of a system thus becomes inseparable from the
history of its transformations. And cognition becomes the
emergence of global states from the application of simple rules (such as Hebb’s
rule) to a network of elements that are just as simple, but very numerous and
highly interconnected. The big difference, compared with cognitivism, is that
connectivism regards the networks of neurons as being not programmed, but trained
(see box below), and regards a mental representation as a correspondence between
an emergent global state and properties of the external world.
with this approach to cognition, the notion of representation was to become increasingly
problematic .Because according to Minsky himself, the brain’s main activity
consists in performing modifications on itself continuously. What you experience
today will influence the way you recall a memory which, far from always being
the same, will be a reconstruction
based on the current state of your brain. Moreover, this reconstructed memory
will inevitably affect the way that your brain functions subsequently.
unlike a machine that manufactures an object that has no effect on the machine’s
operation, the brain is a machine whose processes constantly alter its subsequent
In other words,
with the brain, the results of processes become the processes themselves. Our
cognitive processes are regarded not as representing a world that exists independently,
but as causing the emergence of a world as something inseparable from the structures
that embody the cognitive system. This perspective has led some researchers to
seriously question whether there even is a pre-existing world from which the cognitive
system extracts information. For example, in response to this tenacious metaphor
of a cognitive agent that could not survive without a map of an external world,
Varela developed his theory of enaction.
Unlike traditional artificial intelligence,
in which all of the operations had to be written in advance by a programmer, artificial
neural networks are not programmed, but rather trained. And for many
tasks, such as face recognition, this approach has proven productive.
It would be very hard to define explicit rules for the way that we so readily
recognize a characteristic such as a person’s gender from looking at their
face. The connectionist approach provides far better results. The first step is
to train the network of artificial neurons by showing it a series of photographs
of faces and asking it to determine the sex of the people concerned. The next
step is to tell it what mistakes it has made in performing this task. The network
will then adjust the efficiency of the connections in its circuits to correct
its errors and produce increasingly accurate responses.
In this particular example, a minimum network might consist of three layers of
neurons, in which every neuron can make connections to several other neurons in
the next layer. The first layer should have a large number of elements that can
correspond fairly precisely to the dark and light areas in the photographs that
the network is to be shown. The third layer—the output layer—should
have only two elements, corresponding to the two genders. The second layer, between
these two, would contain an indeterminate number of elements for which the efficiency
of the connections with the elements in the two other layers can be adjusted during
the training process.
If the training photographs
are well chosen, then the network will be able to correctly recognize the genders
of the people in new photographs that it is shown—even if the programmers
won’t be able to describe in detail how the network is finding the right
answers. Because unlike traditional software applications, connectionist networks
don’t do only what their programmers tell them to do. They devise some of
the winning strategy themselves.
“Men are aware of their own
desires and ignorant of the causes by which those desires are determined.”
- Baruch Spinoza (1632-1677)
To demonstrate that change
blindness can occur in everyday life, Daniel Simons devised several
clever experiments. In one of these, an experimenter disguised as a construction
worker approaches a pedestrian, pulls out a map, and asks him how to get somewhere.
While the pedestrian starts to provide directions while looking and pointing at
the map, two other experimenters, also disguised as workers, walk in between the
first experimenter and the pedestrian while carrying a wooden door that momentarily
blocks his view. At that moment, the first experimenter quickly changes places
with one of the two others, whose face was hidden by the door. While the first
experimenter slips away hidden behind the door, the second emerges, also holding
a map in his hand. What happens then is pretty surprising: in about half of the
trials, the pedestrian doesn’t even notice that it’s no longer the
same person and continues providing directions as if nothing had happened!
has also demonstrated another disturbing phenomenon, inattentional
blindness, in an equally spectacular fashion.
Change blindness to a given
object can be diminished when the object has more meaning for the individual
concerned (for example, a cigarette lighter for a smoker, as opposed to a non-smoker).
This suggests that the semantic value of an object for an individual helps that
individual to extract it from the surrounding chaos.
phenomenon of your change blindness for a given object diminishing when that object
has a subjective meaning for you probably comes into play in advertising. But
the reverse situation —for example, if you became convinced that a given
product was of no use to you—might well send it back into the unconscious
chaos of things with no useful meaning that you come across every day but do not
even notice. The meaning of a thing, its affective value for you, thus influences
your conscious perception of it. And this holds true just as much for letting
it enter your consciousness (for example, in an advertisement for a product that
might interest you) as for keeping it out (for instance, when intellectually protecting
yourself from political propaganda).
When individuals are exposed to
a stimulus repeatedly without any consequences or positive reinforcement, they
learn any possible associations with this stimulus more slowly. This phenomenon,
known as latent inhabiting, has been observed
in a wide variety of mammals, ranging from mice to humans.
explanations have been offered as to why it is harder to form new associations
with a stimulus that you have previously judged to be meaningless. Most of these
explanations emphasize the adaptive value of this phenomenon, which removes from
the field of conscious attention anything that is not directly useful for the
task at hand. Latent inhibition also highlights the fact that the meaningfulness
of certain things for an individual is learned, and not given a priori.
This unconscious sorting process keeps you from being
so constantly assailed by inconsequential stimuli that you cannot focus on what
is essential. Examples of this process include the way you smell the particular
scent of a house when you first enter it, or hear the ticking of a clock on the
nightstand when you first go to bed, but soon stop noticing them.
More and more experiments have demonstrated
priming effects that are completely unconscious. In
one such study, subjects on their way to a test where they were supposed to evaluate
the sociability of strangers were stopped by the experimenter’s accomplice
just before they entered the laboratory. The accomplice had his hands full and
asked each subject to help him for a moment by holding his cup of coffee, which
was hot in some cases and cold in others. The results of this study showed that
those subjects who had held a cold cup of coffee assessed the strangers in the
test as being colder, less sociable, and more egotistical than did the subjects
who had held a hot cup of coffee!
also been able to influence other behaviours in a particular direction without
the subjects’ becoming conscious of it. In one such experiment, the test
group of subjects filled out a questionnaire in a room where there was a smell
of lemon-scented cleaning liquid, while the control group filled out the questionnaire
in a room where there was no particular smell. After completing the questionnaire,
both groups were rewarded with a snack of cookies that crumbled very easily. The
film of the subjects eating their snacks showed that the subjects who had been
in the room with the cleaning-liquid scent were three times more likely to sweep
up their cookie crumbs than the subjects in the control group.
experiments and many others (follow the link below) reveal an unconscious brain
that is far more active in choosing
our behaviours than was once believed. A myriad of sensory indications
that we do not perceive consciously might thus explain why we can be friendly
and courteous in one situation but rude and irritated in another, even though
we consciously perceive the two situations as similar. In such cases, perhaps
one of these unconscious circuits that can guide our behaviour has been triggered
by something without our knowing it.
When you are faced with a complex
problem, are you better off trying to consciously make the best choice,
or going with your intuition (in other
words, your unconscious processes)? To try to answer this question, psychologist
Ap Dijksterhuis asked a group of subjects to choose the best
car by using a large file of information to consider a dozen different criteria
carefully. After closing the file, half of the subjects were asked to think for
a few moments before making their choice, while the other half were asked to do
a puzzle (to prevent them from thinking about all that information).
found that the second group—the subjects who did not consciously ponder
the problem—made the better choices! His explanation was that those subjects
who had to make their decisions through conscious reasoning became so overloaded
by all the information that some of the information they considered was not the
most relevant. In this case, unconscious processes, which can deal with large
volumes of information automatically, seem to have been capable of a better synthesis.
These results are consistent with those obtained by
Antonio Damasio and with his theory
of somatic markers, which states that we naturally rely on our emotions,
which are expressed implicitly, to make our rational choices. Should we therefore
give more importance to our intuition than to our reason? Not always, because
in the reverse situation, where there are very few criteria for making a choice
(between two dinner napkins, for example), conscious, controlled deliberation
has proven more effective.
FLAWS IN THE CLASSICAL MODEL OF CONSCIOUSNESS
The development of
the neurosciences as a major discipline within the cognitive
sciences has gradually revealed the flaws in the classical
model of consciousness. The neuroscientific data provided by brain-imaging
experiments and many other experiments do not remotely agree with the idea that
all of our mental processes are consciously accessible to us, or that our consciousness
springs from a point in our brain as the result of our transparent perception
of the world, or that the intentions that we can access consciously are sufficient
causes for our behaviours.
we experience consciously may in fact be only the tip of an iceberg whose submerged
portion consists of countless unconscious processes. The following paragraphs
describe some phenomena that show these unconscious processes at work. These phenomena
are often quite complex, and these descriptions will be quite brief, but they
will nevertheless demonstrate the many flaws in the classical model of consciousness.
Note that the processes in question are described here as “unconscious”
not in the sense that this word has in psychoanalysis,
but simply because they are not subject to our conscious control.
first phenomenon that we will examine involves situations where the conscious
perception changes while the stimulus presented does not. As we shall
see, such cases of rival perceptions pose problems for the classical model of
consciousness. The phenomenon of binocular
rivalry is an example of rival perceptions. In the experimental protocol
used to study binocular rivalry, the subject looks into a special pair of binoculars
in which each eyepiece presents a different image to each eye. This is a very
artificial situation, because it not only separates the fields of vision of the
two eyes but also presents them with differing information.
these conditions, the subject’s subjective perception will alternate between
two states: sometimes the subject will see the image presented to the left eye,
and other times the image presented to the right. This would be a pretty strange
result, if the classical model were correct in describing conscious perception
as a “transparent window on the world”. Which world would be the real
one here: the one seen by the left eye, or the one seen by the right?
Another interesting detail: if, while
this experiment is in progress, the subject’s brain activity is recorded,
and they are asked to indicate which of the two images they are perceiving at
given times, the activity observed in certain areas of their brains will vary
according to the subjective experience that they report. This difference observed
at the neuronal level thus reflects only the difference in subjective perception,
because the objective stimulus has not changed.
The Necker cube is another example of two rival perceptions
that can arise from the same stimulus: a first perception in which you see the
upper surface of the cube, and a second in which you see the bottom one.
Scientists have also discovered
some situations where the reverse occurs: the conscious perception doesn’t
change, even though the stimulus does. This phenomenon, known as change
blindness, sheds further doubt on the classical model’s unitary,
detailed view of our consciousness of the world.
is true that when you look at a landscape, you have the impression of being aware
of the entire scene in all its rich detail. And it is also true that if something
appears in or disappears from the scene, you notice it immediately. The human
visual system is indeed very sensitive to anything that creates an impression
of movement in the scene, such as the appearance or disappearance of an object
as in the animation below. When
such an event occurs, you immediately turn your glance in the direction of the
change, to try to identify it.
But what happens if you very briefly
insert an empty screen between the two images? You thus artificially mask the
appearance or disappearance, because the entire scene disappears for a moment,
then quickly reappears, but with one object added or subtracted. Try this yourself
by clicking the button below the image to the right. Did you notice the change
fact that the mask makes it so much harder to identify what is changing in the
scene suggests that, contrary to what the classical model of consciousness would
have us believe, at any given moment we are processing only a small proportion
of a visual scene consciously. We are thus never actually forming a detailed visual
representation of the entire scene.
believe that the reason we have this illusion of being fully conscious of the
entire scene is that we know that at any time, we can shift our attention from
one point to another in the scene to check the details. According to these scientists,
we are in a sense using the world itself as a form of external memory. We are
also, in their view, processing the entire scene at all times, but only at a preconscious
level that would let us identify certain details in it consciously if we wanted
Lastly, the sidebar on the research done by Daniel
Simons shows that change blindness can also be observed outside the laboratory,
in particular interpersonal situations.
illusions are another common phenomenon that does not fit at all with the
idea of consciousness as a faithful reflection of the reality that surrounds us.
The very essence of an optical illusion is to give us a conscious perception that
is incorrect, and hence different from reality. One can readily see the problem
that this raises for the classical model of consciousness.
But curiously, though our conscious perception
of the size of the two chips may be influenced by this optical illusion, that
is not the case for the actions that we direct toward them when they
are presented as 3D objects through the effect of perspective, as in the image
you were asked to try to pick up either of the yellow chips in this 3D picture,
and the distance between your fingers when you performed the corresponding movement
were measured, this distance would reflect the actual size of the chip,
regardless of which of the two contexts it was presented in.
This result indicates that “visual
perception” and “visually-guided
action”can be dissociated from each other. In other words, behaviours
such as picking up an object are not misled by the erroneous conscious perception.
It follows that these behaviours must be controlled by processes that escape consciousness.
example of this phenomenon is the old joke that if you want to ruin your opponent’s
concentration in a tennis match, for example, all you have to do is compliment
him on the accuracy of his serve, the smoothness of his return, and so on. Usually,
that will make him self-conscious. He will start trying to use conscious movements
to match the perfect accuracy of the movements that he makes unconsciously from
years of constant practice, and he’ll end up sending the ball into the net!
The existence of an unconscious aspect of vision is
also revealed in spectacular fashion by the phenomenon of “blind
vision”. People who have blind vision have suffered damage to either
their left or their right primary
visual cortex and have consequently lost their sight in the opposite
visual hemifield. But in experiments where a light stimulus is sometimes presented
to such people’s blind hemifield and sometimes not, and they are asked to
“take a chance” each time and say whether or not such a stimulus was
present, they will respond accurately much more often than would happen at random!
And when they are told how accurate their answers have been, they remain incredulous,
convinced that they must have made random lucky guesses, because they say that
they had seen nothing at all in that part of their visual field.
with blind vision thus have some surprising residual visual capabilities. These
capabilities appear to be made possible by the subcortical visual structures and
by some neural pathways that lead directly from the lateral
geniculate nucleus to visual areas V4 and V5, without passing first through
primary visual area V1.
Thus, though the primary visual
areas seem to be essential for conscious vision, there are a number of vision-guided
behaviours that do not seem to require any conscious control. But how is this
possible? Isn’t consciousness suppose to arise first, and action flow from
it after that? Yet another chink in the armour of the classical model of consciousness!
there are more. Just as with perception, there are entire areas of learning
and memory that take place outside the realm of consciousness. First of all,
at any given time, most of our memories are unconscious. We can remember them
consciously, but they spend most of their time as unconscious traces
in our nervous systems.
Second, there are the numerous
forms of memory . Simply acquiring a particular skill, such as bicycle
riding or touch typing, involves procedural
memory that we cannot access consciously. The same is true for the priming
effect, in which past exposure to a relevant piece of information
influences our cognitive processes without our even realizing it (see sidebar).
For example, if you are given a long list of words to memorize, and one of these
words recurs several times in the list, you will find it easier to recall this
word, even if you didn’t consciously notice that it occurred more often
than the others. (A good portion of advertising is based on this principle of
unconscious preferential recognition.)
thus seems clear that we accomplish a multitude of tasks unconsciously, and that
these unconscious processes are far more numerous than our conscious actions.
might be cited as a final example which also shows that the two kinds of processes,
conscious and unconscious, can be at work simultaneously. Because if you think
about it, when you are having a conversation, you are forming conscious thoughts
as the same time as you are using the syntax
and vocabulary of your mother tongue completely automatically.
these many manifestations of unconscious processes, we can therefore, as a first
approximation, distinguish not one but two sub-systems. The first one is conscious,
often verbal or visual, and operates serially (“You can’t
think of more than one thing at a time.”). The second is largely unconscious,
often affective, and responds to stimuli automatically. It is composed of numerous
units operating as massively parallel processors, so that it
has a much greater processing capacity.
that the majority of our cognitive processes are in fact unconscious
is regarded as a veritable revolution that has ended the reign of the classical
model of consciousness. This unconscious part of our minds, which is also far
more “intelligent” than had previously been believed (see sidebar
on difficult choices), continues to amaze scientists with the diversity of its
processes: mental and sensorimotor automatisms, implicit knowledge and even implicit
reasoning, semantic processing, and so on.
two sub-systems, the conscious and unconscious, do not suffice all on their own
to manage the complexity of the real world that is so vastly underestimated by
the classical model of consciousness. They are therefore supported by another
system, composed of what are called our attentional
data show that certain aspects of consciousness that seem unitary are
in fact dissociable. For instance, patients with brain
damage can sometimes display a complete dissociation between their performance
and their awareness of this performance.
conscious visual perception, for example. There is a perception disorder called
visual form agnosia (or aperceptive agnosia), in which the patient
cannot visually recognize the size, shape, or orientation of an object. Yet despite
this major information deficit concerning the object, the person can still grasp
it perfectly between his or her thumb and index finger.
are also cases of the reverse condition, optical ataxia,
in which people cannot reach or grasp an object but can visually recognize its
size, shape, and orientation.
In both cases, there
is a complete dissociation between the conscious perceptive processing and the
unconscious visual/motor processing. This same distinction is also found in the
brain’s anatomy, between the ventral
visual pathway and the dorsal
is an even more global syndrome in which the patient flatly denies the existence
of a deficit that he or she has acquired as the result of a neurological injury.
This was the case for a patient who was treated by V.S.
Ramachandran. This patient had a paralyzed left arm, as the result
of a stroke in the right hemisphere (anosognosia is almost always the result of
a right-hemisphere injury). When Ramachandran asked her to point to him with her
right arm, she did so without any problem. When he asked her to do so with her
paralyzed left arm, however, that arm of course remained immobile, but she insisted
that she had followed the instruction. And if Ramachandran told her that her left
arm hadn’t moved, she answered that she had arthritis in her left shoulder,
that it was causing her pain, and that he knew so very well.
to the right hemisphere can also cause another spectacular type of dissociation:
Patients with hemineglect simply can no longer consciously perceive the left half
of their universe. For example, a man with hemineglect will shave only the right
side of his face and eat only the food on the right side of his plate. If asked
to draw a clock, he will cram all 12 hours into the right half of the dial. And
if someone seated to his left speaks to him, he will respond to the person seated
to his right.
Hemineglect also differs from another
elementary perceptual disorder such as hemianopsia (loss of sight
in half of the visual field). When presented with a printed sentence, people with
hemianopsia will turn their head in order to see the whole sentence, whereas people
with hemineglect will read only the words in the right-hand portion of the sentence.
What makes hemineglect of interest for the study of
consciousness is that the information that its victims overlook consciously, they
seem to process unconsciously nevertheless. For example, if they are shown two
pictures, one to their left and one to their right, they will be unable to identify
the one to their left. But curiously, if you ask them to take a chance and guess
whether the image on the left was the same as the one on the right, they will
guess correctly far more often than would happen randomly. And other experiments
have suggested that the brains of people with hemineglect can unconsciously process
not only the basic physical traits of images, but more elaborate semantic information
as well. These people thus show that there can be a disassociation between performance
and awareness of performance. Such a finding may seem paradoxical if we assume
the classical model of consciousness, but becomes intelligible when we adopt a
more distributed model of the substrates of consciousness in the brain.
Another strange syndrome, prosopagnosia, occurs when someone
suffers brain damage that makes them unable to recognize faces, even of people
whom they know well. But when they are shown a picture of a friend’s face,
even though they will consciously say that they are seeing that face for the first
time, physiological signs such as minute changes in the moistness of their hands
(as measured by variations in their skin conductance) show that they have actually
recognized the face anyway—yet another example of the dissociation between
unconscious and conscious performance.
such as schizophrenia provide other examples of dissociation
that help us to understand consciousness. People with schizophrenia often attribute
the intentions behind their actions not to themselves but to forces outside themselves.
Several authors have tried to explain this aspect of schizophrenia in terms of
a dissociation between an intentional system that is the source of the action
and a “self”control system that is not being informed of the individual’s
There are some other, rare types of dissociations
that are truly bizarre, such as strange-hand syndrome, in which
people have the impression that one of their hands is no longer under their control.
Such people may, for example, watch with fright as their hand performs a complex
task such as unbuttoning their shirt, when they are convinced that they did not
give it the order to do so. In this pathology, which often involves damages to
the corpus callosum (as in people with a split
brain), the hand’s action is perceived as responding to a foreign
Yet another spectacular form of dissociation
is dissociative fugue, most common in Hollywood movies but nevertheless
possible in real life (it affects approximately 2 out of every 1000 people in
the United States). In extreme cases, someone may leave their home, travel a long
distance, and start a new life while being totally or partially amnesic about
their previous one.
Certainly one of the best known
forms of dissociation is dissociative identity disorder (formerly
known as multiple personality disorder). People with this disorder alternate among
two or more personalities without being able to control these changes. Each of
these personalities usually has its own range of behaviours and does not share
its explicit knowledge with the other personalities. But a transfer of information
among the various personalities may take place in implicit memory. Once again,
conscious and unconscious do not necessarily go together.
how strange can dissociative disorders get? Perhaps the strangest is Body
Integrity Identity Disorder, or BIID, in which an individual requests
the elective amputation of a body part that they say does not match the idealized
image that they have of themselves. Paradoxically, these people do not feel complete
until the day they succeed in getting the amputation.
When a correlation
is found between a conscious experience and a neural event (in other words, when
they are found to co-occur regularly), it must be interpreted cautiously, because
can mean various things. It could mean that the neural event causes
the conscious experience. It could mean that the conscious experience causes the
neural event. It could mean that some third event causes both the neural event
and the conscious experience. Lastly, the neural event and the conscious experience
may actually be the same thing, even if the two don’t seem at all alike.
SOME PROMISING CONCEPTS AND MODELS FROM THE NEUROSCIENCES
To develop neurobiological
models of consciousness, scientists start by looking for what are called neural
correlates of consciousness. This consists in identifying variations
that always occur in the activity of certain specific groups of neurons when a
particular piece of conscious content appears. For example, some experimental
protocols commonly used to identify neural correlates of conscious visual perception
are binocular rivalry, change
blindness, and bistable images (images that can be interpreted in two different
True neurobiological models of consciousness
must be distinguished from such simple neural correlates of consciousness. True,
identifying correlations between the activity of certain groups of neurons and
certain subjective or phenomenological
properties of consciousness can help to define what is plausible when one
is developing a model. But the identification of such correlations does not automatically
produce a comprehensive explanation that relates these neuronal activities to
the phenomenon of consciousness.
such explanations requires more general models that try to explain the many facets
of consciousness by combining data from all branches of the contemporary cognitive
neurosciences. Most of these models began to be developed in the early 1990s,
in the wake of the first international conferences devoted essentially to the
study of consciousness, like the one announced in the poster below.
Dennett, consciousness is about “fame in the brain”.
At any moment, thousands of mental objects are forming and dissolving everywhere
in the brain as they engage in a Darwinian competition with one another. The “self”
might be regarded as what emerges from this competition. Thus, at any given time,
there are many possible conscious states, but only one of these multiple
versions will get its moment of glory and become “famous”,
i.e., conscious, for the space of a second. According
to this model, consciousness cannot be located precisely in time or in any particular
part of the brain, which thus totally excludes classical,
“Cartesian theatre” models of consciousness .
According to global workspace theory,
consciousness becomes possible when these various subsystems pool certain results
of their operations in a single, “global workspace”. When these results
are expressed in this forum, they become accessible to the brain as a whole, and
therefore conscious. Much like Dennett’s “multiple versions”,
various elements enter into competition to capture our attention, depending on
our interests of the moment, but only one at a time can occupy the global workspace,
which explains why we can be conscious of only one thing at a time.
and Dehaene attempted to describe the various states that can be observed in this
connectionist model of consciousness
and then tried to identify the mechanisms that let the mind pass from one of these
states to another. In contrast to Baars’s
model and to several other brain-imaging studies that simply distinguished one
conscious state from multiple unconscious ones, Changeux and Dehaene’s model
distinguishes three different possible states of activation:
Dehaene et al., 2006
a first, subliminal processing state in which there is not enough
activation to trigger wide-scale activation of the network;
- a second,
preconscious state in which there is enough activation to access
consciousness, but that is temporarily kept from doing so by a lack of top-down
- a third, conscious state that penetrates
the global workspace when a preconscious stimulus receives enough attention to
cross the consciousness threshold.
Crick and Christof Koch also examine the neural correlates of consciousness,
but their emphasis is on the circuits
of the visual system. For Crick and Koch, the key to conscious processes lies
in the synchronized neuronal oscillations that occur in the cortex
at frequencies around 40 Hertz (35 to 75 Hz).
visual areas of the brain that respond to various visual characteristics of the
same object (form, colour, movement, etc.) do in fact fire synchronously at a
particular frequency. And if there is another object located just beside the first
one in the person’s field of vision, then other neurons in that person’s
visual areas also fire synchronously, but
not at the same moments as the neurons associated with the first object.
Llinás focuses on a global form of neuronal synchronization that might
prove essential for determining which particular perception becomes conscious.
According to Llinás, the thalamus triggers cortical oscillations that sweep
the brain from front to back in 25 milliseconds—in other words, 40 times
per second, the same 40-Hz frequency that has often been associated with the conscious
perceptual unit. Thus, in addition to the cortical oscillations
that bind the various aspects of a perceived object together, there would be this
second type of synchrony between a given neuronal
assembly and these non-specific thalamic oscillations. The
assembly that is in phase with these non-specific oscillations would then be the
one that becomes conscious.
Edelman accords less importance to the specific activity of certain neurons
than to the general organization of the brain’s circuits. He starts from
the premise that consciousness has not always existed and that it appeared at
some time in the course of the evolution of species just as it appears at a given
time in the development
of individual human beings. Edelman then attempts to identify the new brain
architectures that led to the emergence of consciousness.
to Edelman, a selective mechanism that he calls “neural darwinism”
(follow the Tool Module link to the left) creates a system of neural maps composed
assemblies that are responsible for our various perceptual abilities. When
the brain receives a new stimulus, several of
these maps are activated and send signals to one another. Edelman uses the term
“re-entrant loops” to designate this pattern of interconnections
among the various neural maps. The reciprocal connections between the thalamus
and the cortex, also known as thalamocortical
loops, are central to this model of “re-entrant maps” whose looping
operation constitutes the starting point for consciousness, according to Edelman.
in Edelman’s view, consciousness is associated not with a permanent anatomical
structure, but rather with an ephemeral activity pattern that is present at various
locations in the cortex where these re-entrant loops permit. That is why Edelman
and his colleague Giulio Tononi instead describe these conscious processes in
terms of a “dynamic core”.
dynamic view of consciousness is also taken by Walter
J. Freeman, who uses the mathematics of non-linear dynamics to
interpret the neuronal oscillations associated with conscious phenomena. According
to Freeman, the brain responds to changes in
the world by destabilizing its primary sensory cortexes. The resulting new, chaotic
oscillation patterns give the impression of being noise, but actually hide an
underlying order from which new meanings are constructed continuously.
thus plays the role of an operator who modulates these cerebral dynamics. Residing
both nowhere and everywhere, this operator is continuously re-forming conscious
contents that are supplied by the various parts of the brain and that undergo
the rapid, extensive changes that we associate with human thought.
conscious thought and the decisions that arise from it do not involve abstract
reasoning alone. For Antonio
Damasio, one cannot speak of consciousness without including the constant
monitoring of an affective loop in which the brain and the body engage in a continuous
dialogue (via the autonomic
nervous system, the endocrine system, etc.).
champions the idea that our conscious thoughts depend substantially on our visceral
perceptions. For him, consciousness develops through the brain’s monitoring
of internal somatic states (notably via the insula),
and this monitoring has evolved because it lets us uses these somatic states to
mark, or evaluate, our external perceptions. Damasio thus uses the concept of
somatic markers to describe how the emotions of our inner world
interact with our perceptions of the outside world.
last concept, which gives the body and the environment an even more extensive
role in the genesis of conscious processes, is called enaction.
It was developed by Francisco
Varela and is part of the intellectual current known as embodied cognition. The central idea of enaction is that the
cognitive faculties develop because the body interacts with a given environment
in real time.
From the enactive perspective,
perception has nothing to do with passive reception but is inextricably linked
with the way that the body/brain system guides its own actions in the local situation
of the moment. In the terminology of enaction, our senses enable us to “enact”
meanings—in other words, to modify our environment while also being constantly
shaped by it.
The essence of cognition
and consciousness therefore cannot be found in representations of a world completely
external to ourselves, nor solely in a particular neuronal organization, but instead
depends on all of the organism’s sensorimotor structures and its capabilities
for bodily action, coupled with a particular environment.