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Can Information Theory Explain Consciousness?


The problem of consciousness remains with us. What exactly is it and why is it still with us? The single most important question is: How exactly do neurobiological processes in the brain cause human and animal consciousness? Related problems are: How exactly is consciousness realized in the brain? That is, where is it and how does it exist in the brain? Also, how does it function causally in our behavior?

Collection of Arturo Schwarz, Milan/Scala/Art Resource
Tristan Tzara: Self-Portrait, 1928

To answer these questions we have to ask: What is it? Without attempting an elaborate definition, we can say the central feature of consciousness is that for any conscious state there is something that it feels like to be in that state, some qualitative character to the state. For example, the qualitative character of drinking beer is different from that of listening to music or thinking about your income tax. This qualitative character is subjective in that it only exists as experienced by a human or animal subject. It has a subjective or first-person existence (or “ontology”), unlike mountains, molecules, and tectonic plates that have an objective or third-person existence. Furthermore, qualitative subjectivity always comes to us as part of a unified conscious field. At any moment you do not just experience the sound of the music and the taste of the beer, but you have both as part of a single, unified conscious field, a subjective awareness of the total conscious experience. So the feature we are trying to explain is qualitative, unified subjectivity.

Now it might seem that is a fairly well-defined scientific task: just figure out how the brain does it. In the end I think that is the right attitude to have. But our peculiar history makes it difficult to have exactly that attitude—to take consciousness as a biological phenomenon like digestion or photosynthesis, and figure out how exactly it works as a biological phenomenon. Two philosophical obstacles cast a shadow over the whole subject. The first is the tradition of God, the soul, and immortality. Consciousness is not a part of the ordinary biological world of digestion and photosynthesis: it is part of a spiritual world. It is sometimes thought to be a property of the soul and the soul is definitely not a part of the physical world. The other tradition, almost as misleading, is a certain conception of Science with a capital “S.” Science is said to be “reductionist” and “materialist,” and so construed there is no room for consciousness in Science. If it really exists, consciousness must really be something else. It must be reducible to something else, such as neuron firings, computer programs running in the brain, or dispositions to behavior.

There are also a number of purely technical difficulties to neurobiological research. The brain is an extremely complicated mechanism with about a hundred billion neurons in humans, and most investigative techniques are, as the researchers cheerfully say, “invasive.” That means you have to kill or hideously maim the animal in order to investigate the operation of the brain. Noninvasive research techniques, such as brain imaging, are useful, but they have so far not given us the sort of detailed understanding of the workings of the conscious mind that we would like.


Christof Koch has written about these issues before, including an important book I reviewed in these pages, The Quest for Consciousness.1 His current book abandons the biological approach he adapted earlier, and which I have articulated above. According to his current view, consciousness has no special connection with biology. He follows the Italian neuroscientist Giulio Tononi,2 now at the University of Wisconsin–Madison, in thinking that the key to consciousness is information theory, which, he writes, “exhaustively catalogues and characterizes the interactions among all parts of any composite identity.” It does so by quantifying the information about such interactions as “bits” that can be measured, stored, and transmitted. The application of information theory made by Tononi and Koch emphasizes that consciousness requires that the information that constitutes consciousness should be both “differentiated” and “integrated.” In one of Tononi’s examples, in experiencing a red square we “differentiate” the property of redness and the property of squareness, but the experience is “integrated” in that it “cannot be decomposed into the separate experience of red and the separate experience of a square.” Tononi goes on,

Similarly, experiencing the full visual field cannot be decomposed into experiencing separately the left half and the right half: such a possibility does not even make sense to us, since experience is always whole.

According to Koch, any system at all that has processes describable by information theory is, at least to some degree, conscious. But since any system that has causal relations can be described in the vocabulary of information theory, it turns out that consciousness is everywhere. Panpsychism follows. As he tells us:

By postulating that consciousness is a fundamental feature of the universe, rather than emerging out of simpler elements, integrated information theory is an elaborate version of panpsychism.… Once you assume that consciousness is real and ontologically distinct [i.e., exists apart] from its physical substrate, then it is a simple step to conclude that the entire cosmos is suffused with sentience. We are surrounded and immersed in consciousness….
No matter whether the organism or artifact hails from the ancient kingdom of Animalia or from its recent silicon offspring, no matter whether the thing has legs to walk, wings to fly, or wheels to roll with—if it has both differentiated and integrated states of information, it feels like something to be such a system; it has an interior perspective.

In other words it is conscious. So:

personal computers, embedded processors, and smart phones…might be minimally conscious.

Koch and Tononi begin by investigating biological consciousness in humans and animals. They develop a theory that consciousness is information. But such information is not confined to biological systems. You also find consciousness in, say, smartphones. So, in the end, for these authors, there is nothing especially biological about consciousness.

The integrated information theory of consciousness makes a number of important predictions. Among them is that, in the specific case of biological consciousness, information arises from causal interactions within the nervous system, and when those interactions cannot take place anymore the amount of consciousness shrinks. For example, there is less consciousness in deep sleep than in wakefulness. According to Tononi this is because there is less integration going on in the brain in deep sleep compared with that in wakefulness. Tononi and his colleague Marcello Massimini, now a professor in Milan, set out to prove this by attaching electrodes to volunteers both sleeping and awake. A difference of results, according to Tononi, showed that in deep-sleeping subjects the integration breaks down.

Koch discusses a number of other issues in the book: notably free will, the relation of science and religion, and the role of unconscious mental processes. I will discuss some of these later, but the single most important claim is the analysis of consciousness based in information theory.


Two objections stand out immediately. The first is that no reason has been given at all why there should be any special connection between information theory and consciousness. In his earlier views, Koch argued that consciousness is explained by synchronized neuron firings. Now he objects to that previous view. The objection is: Why should there be any connection between certain rates of neuron firings and consciousness? The same question arises with information theory: Why should information theory give us the essence of subjectivity? What is the connection supposed to be? My second objection is that the theory implies panpsychism, and pansychism is absurd for a reason I can explain briefly.

Consciousness comes in units. The qualitative state of drinking beer is different from finding the money in your wallet to pay for it. But a consequence of its subjectivity is its unity. So for example, I am conscious and you are conscious but each consciousness is separate from the other; they do not smear into each other like adjoining puddles of mud. Consciousness cannot be spread over the universe like a thin veneer of jam; there has to be a point where my consciousness ends and yours begins. For people who accept panpsychism, who attribute consciousness, as Koch does, to the iPhone, the question is: Why the iPhone? Why not each part of it? Each microprocessor? Why not each molecule? Why not the whole communication system of which the iPhone is a part? The problem with panpsychism is not that it is false; it does not get up to the level of being false. It is strictly speaking meaningless because no clear notion has been given to the claim. Consciousness comes in units and panpsychism cannot specify the units.


Christof Koch describes his book as the “Confessions of a Romantic Reductionist.” But this is misleading. His book is explicitly and aggressively antireductionist, it contains no confessions, and if you are looking for a romantic book—this is not it. A crucial sentence is this:

Experience, the interior perspective of a functioning brain, is something fundamentally different from the material thing causing it and…it can never be fully reduced to physical properties of the brain.


I believe that consciousness is a fundamental, an elementary, property of living matter. It can’t be derived from anything else; it is a simple substance, in Leibnitz’s words.

This is antireductionism with a vengeance. Indeed, as he himself says, it is a form of dualism. You are reductionist if you think that consciousness is really something else, and that the first-person ontology—the sense I have that I exist—can be shown to be third-person ontology—my sense is reducible to something else. Favorite candidates for reducing consciousness to something else are neuron firings, computer processes, and behavior. Antireductionism does not become reductionism by being described as “romantic.” There is no sense whatever—romantic or otherwise—in which Koch is a reductionist about consciousness.

Also, I could not find any confessions in the book. “Confessions” implies that he admits he has done something wrong. There are many personal reflections in the book about himself, his family, his children, his dogs, his mountain-climbing experiences, and his work as a scientist. His friends, of whom I am one, will find many of these quite moving. But any confession where he actually admits to some serious or even trivial misdeed is conspicuously absent from the book. An accurate subtitle would be “Personal Reflections of a Scientific Dualist.”


On the question of free will, Koch endorses the most extreme of interpretations of the experiments conducted by the late neuroscientist Benjamin Libet, whose experiments drew on the work of other scientists. Libet would tell his subjects to perform some intentional but trivial act, such as pushing a button or flicking their wrist, and to do it every so often whenever they feel like it. But he asked them to observe on a clock exactly the point at which they made up their mind to do it and he found that at exactly the point at which the intention in action began, there was an interval between increased brain activity in a specific area of the brain and the awareness by the subject that he is beginning to push the button or perform a similar action. In short, before I was aware that I was about to push the button, my brain was getting ready to do so. The brain has an extra activity, called the “readiness potential,” prior to the reported awareness of the onset of the action. This can last a couple hundred milliseconds or sometimes even longer.

  1. 1

    Robert and Company, 2004; see my review in these pages, January 13, 2005. 

  2. 2

    Giulio Tononi, “Consciousness as Integrated Information: A Provisional Manifesto,” The Biological Bulletin, Vol. 215, No. 3 (2008). 

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