Consciousness: Confessions of a Romantic Reductionist (The MIT Press)

by Christof Koch

your eyes see details your mind is unaware of. In

The volunteer herself was unaware of the second shift in the light’s position because vision is partially shut down during saccades. (That’s why you can’t see your eyes move: try looking in a bathroom mirror while shifting your eyes back and forth.)

Earlier clinical work, fortified by experiments in monkeys, gave birth to the idea of two distinct visual processing streams. Both originate in the primary visual cortex but then divide to innervate different regions of the cortex dedicated to higher visual and cognitive functions. One flows through V2 and V3 into the inferior temporal cortex and the fusiform gyrus. This is the perceptual, ventral, or what pathway. The other, the action, dorsal, or where pathway, delivers data to the visual-motor regions in the posterior parietal cortex.

If you think humanity is high-minded, just check out Google’s Zeitgeist archives for the top ten search terms.

No one is an island. Even the recluse defines himself by his relationships with others, if not in real life, then through books, movies, or television.

You might believe as fervently as I did as a young man that your conscious intentions and your deliberate choices control your interactions with family members, friends, and strangers. Yet decades of social psychology research have clearly shown otherwise. Your interactions are largely governed by forces beyond your ken, by unconscious desires, motivations, and fears.

the act of thinking about or observing a behavior increases the tendency to engage in that behavior. This principle of ideomotor action is a natural consequence of the partial overlap of the representations of perception and action in the cerebral cortex.

But even if you try hard to avoid stereotyping, you still harbor unconscious biases and predilections. You can’t escape being a child of your culture and upbringing, soaking up implicit judgments from fairy tales and myths, from books, movies, and games, from your parents, playmates, teachers, and contemporaries. If you don’t believe me, just take an implicit association test (I recommend the Harvard one, which you can find online), in which you answer a bunch of questions as quickly as you can. The test measures, in an indirect, oblique manner that is resistant to manipulation or lying, the extent of your bias for or against a particular religion, gender, sexual orientation, or ethnic group.

First, unconscious dispositions are widespread and automatic, becoming activated in the presence of their triggers. They can be very powerful and shared by entire communities.

Yet more insidious, much more widespread than individual failings to heed warnings, were the explicit and implicit attitudes of racial arrogance and cultural condescension in the minds of the people who could have made a difference. Admiral Kimmel, the officer in charge of the Pacific Fleet, made it perfectly clear in an unguarded moment during one of many congressional investigations: “I never thought those little yellow sons-of-bitches could pull off such an attack so far from Japan.” More than fifty years later, Deputy Secretary of Defense Wolfowitz held his opponents in equal disregard, dismissing bin Laden as “this little terrorist in Afghanistan.” Widespread stereotyping blinded the people in power: “How can uneducated people living in caves with towels on their heads threaten us, the most powerful nation on the planet?” The events that led to the financial meltdown of Lehman Brothers and that almost crashed the markets in September 2008 are another example of such pathology of thought. Here, it was the widely held belief that investment risk was under control and could be leveraged away by suitable financial instruments that led to a global recession.

Self-help movements insist that having a positive and optimistic attitude makes a difference. Although thinking good thoughts will not cure cancer, it will shape your behavior. And that is one reason why I live where I do and do what I do—Americans in general, and the self-selected group of immigrants to the West Coast in particular, believe that with enough desire, sweat, dedication, and the judicious application of technology, almost anything is possible. I share this can-do attitude. To fail when one has given everything one has is honorable; not to try because one is afraid of failure is a major character flaw.

Choice blindness is relevant not only to dating but to life in general. You frequently have little idea why you do the things you find yourself doing. Yet the urge to explain is so strong that you make up a story on the spot, justifying your choice, confabulating without realizing it.

A more cautious reading of the data is that forming a rapid impression and coming to a conscious decision can be better than endlessly second-guessing that first-glance assessment. Make a decision, trust yourself, and stick with it.

Free will is the philosophical theme par excellence. Its roots stretch back to antiquity. It is a topic that, sooner or later, confronts each one of us. Surprisingly, a key aspect of this problem is reducible to a question of perceptual consciousness. To me, this constitutes a major advance in one of the most disputatious problems in metaphysics.

Conceited as they were, they even believed that they, and only they, could escape the iron law of cause and effect that governs everything. They could do this by virtue of something they called free will, which allowed them to do things without any material reason.

Can you truly act freely? Can you do and say things that are not a direct consequence of your predispositions and your circumstances?

Yet the doctrine of predestination, and its secular cousin, determinism, holds that you could not have acted in any other way. You had no true choice in the matter. You are a lifelong indentured servant to an absolute tyrant.

Give me these forces and the current state of a system—physicists’ shorthand for specifying the precise location and speed of all components of the system—and I can tell you the state of that system at any future point in time. This is the essence of determinism. The mass, location, and velocities of the planets as they travel in their orbits around the Sun fully determines where they will be in a thousand, a million, or a billion years from today, provided only that all the forces acting on them are properly accounted for.

This conceptual leap finds its most eloquent proponent in the French mathematician Pierre Simon de Laplace, writing in 1814: We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, and if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes.

The eleventh-century Persian astronomer, mathematician, and poet Omar Khayyam puts it plainly in his Rubaiyat: And that inverted Bowl we call the Sky, Whereunder crawling coop’t we live and die, Lift not thy hands to It for help—for It Rolls impotently on as Thou or I.

It came as a mighty surprise, therefore, when computer modeling in the 1990s demonstrated that Pluto has a chaotic orbit, with a divergence time of millions of years. Astronomers can’t be certain whether Pluto will be on this side of the Sun (relative to Earth’s position) or the other side ten million years from now!

Mark my words—if physical determinism holds, there is no Cartesian freedom. Everything that will ever happen within the universe, including all of your actions, was already inherent at its birth. All events are preordained. You are condemned to watch a movie that is screened exclusively for your benefit and that lasts a lifetime. The director, the laws of physics, is deaf to your pleas to change a single scene.

If a house fly pursued by a predator makes a sudden, abrupt turn in midflight, it is more likely to see the light of another day than its more predictable companion. Thus, evolution might favor circuits that exploit quantum randomness for certain acts or decisions. Random quantum fluctuations deep in the brain, whose consequences are amplified by deterministic chaos, might lead to measurable outcomes.

The roman poet Lucretius postulated his famous “swerve,” the random jerky motion of atoms, in De rerum natura to guarantee, in his words, “will torn free from fate.” Yet indeterminism provides no solace for the true libertarian; it is no substitute for free will. Surely my actions should be caused because I want them to happen rather than happening by chance. Trading the certainty of determinism for the ambiguity of randomness is not what Descartes had in mind. The libertarian conception of the mind requires that the mind controls the brain, not that the brain decides capriciously.

Entangled quantum systems, such as two electrons with opposite spins moving away from each other or two polarized photons, will always be correlated, no matter how remote they are (as long as they don’t interact with anything else in the interim). As soon as the spin of one electron is measured, the spin of the other is determined instantaneously, even though it may be a light-year away. It’s weird, but true. The physicist Roger Penrose, the anesthesiologist Stuart Hameroff, and others have speculated that this otherworldly nonlocality is closely linked to consciousness. Strands of Buddhism, a much older tradition, likewise argue that object and subject are inexorably linked and that consciousness is a fundamental feature of the physical universe.

Whenever the person being tested is about to move a limb, a slowly rising electrical potential builds up. Called the readiness potential, it precedes the actual onset of movement by up to one second.

The results told an unambiguous story. The beginning of the readiness potential precedes the conscious decision to move by at least half a second, and often by much longer. The brain acts before the mind decides! This was a complete reversal of the deeply held intuition of mental causation—the brain and the body act only after the mind has willed it. That is why this experiment was, and remains, controversial. But it has been repeated and refined over the intervening years—a brain-imaging version of the experiment was in the news recently—and its basic conclusion stands.

This is a neglected idea in the free will debate—that the mind–body nexus creates a specific, conscious sensation of voluntary movement, a compelling experience of “I willed this,” or “I am the author of this action.” Like other subjective experiences, this feeling of willing has specific phenomenal content. It has a quale no different in kind from the quale of tasting bitter almond.

In automatism, the sense of agency may be missing altogether. Examples include possession and trance in religious ceremonies, posthypnotic suggestion, Ouija board games, dowsing, and other pseudo-occult phenomena. Participants vehemently deny that they caused these things to happen. Instead, they project responsibility onto distant gods, spirits, or the hypnotist.

In your life, far removed from occult practices, you find yourself doing things without being in the act. This is notably the case when people are deeply conflicted about what they want. The compulsive gambler suddenly finds himself at the casino believing tonight he’ll win big, even though he “knows” at some level that by the time the night is over, he’ll have lost everything.

I’ve taken two lessons from these insights. First, I’ve adopted a more pragmatic, compatibilist conception of free will. I strive to live as free of internal and external constraints as possible. The only exception should be restrictions that I deliberately and consciously impose upon myself, chief among them restraints motivated by ethical concerns; whatever you do, do not hurt others and try to leave the planet a better place than you found it. Other considerations include family life, health, financial stability, and mindfulness. Second, I try to understand my unconscious motivations, desires, and fears better. I reflect deeper about my own actions and emotions than my younger self did.

Philosophy is written in this grand book—the universe I say—that is wide open in front of our eyes. But the book cannot be understood unless we first learn to understand the language, and know the characters, in which it is written. It is written in the language of mathematics. —Galileo Galilei, The Assayer (1623)

We postulated a relationship between awareness and the rhythmic discharge of cortical neurons, firing every twenty to thirty milliseconds. (Our so-called 40-hertz hypothesis is currently enjoying a renaissance in the context of selective attention.)

This cornucopia of behavior and the numerous structural and molecular similarities between the canine and the human brain lead me to conclude that dogs have phenomenal feelings. Any philosophy or theology that denies sentience to them is seriously deficient. (I felt this intuitively as a child; I couldn’t understand why God would resurrect people but not dogs on Judgment Day. It didn’t make any sense.) And what is true for dogs is also true for monkeys, mice, dolphins, squids, and, probably, bees. We are all nature’s children; all of us experience life.

Whereas this argument has less force in Western countries with monotheistic faiths that abjure souls to animals, Eastern religions are more tolerant. Hinduism, Buddhism, Sikhism, and Jainism recognize all creatures as kindred, sentient beings. Native Americans, too, were free of the belief in human exceptionalism that is so strongly rooted in the Judeo-Christian view of the world.

The conceptual difficulty of understanding how consciousness emerges from the brain has a historical analogue in the debate raging in the nineteenth and early twentieth centuries about vitalism and the mechanisms of heredity. The chemical laws underlying heredity were deeply perplexing. How was all the information specifying a unique individual stored in a cell? How was this information copied and passed on to the cell’s descendants? How could the simple molecules known at that time enable the egg to develop into an adult?

Chemists could not imagine that the exact sequence of four types of nucleotides in a string-like molecule held the key. Geneticists underestimated the ability of macromolecules to store prodigious amounts of information. They failed to comprehend the amazing specificity of proteins shaped by the action of natural selection over several billion years. But this particular puzzle was eventually solved. We now know that life is an emergent phenomenon and can, ultimately, be reduced to chemistry and physics. No vitalistic force or energy separates the inorganic, dead world from the organic world of the living.

Functionalism applied to consciousness means that any system whose internal structure is functionally equivalent to that of the human brain possesses the same mind. If every axon, synapse, and nerve cell in my brain were replaced with wires, transistors, and electronic circuitry performing exactly the same function, my mind would remain the same. The electronic version of my brain might be clunkier and bigger, but provided that each neuronal component had a faithful silicon simulacrum, consciousness would remain. It is not the nature of the stuff that the brain is made out of that matters for mind, it is rather the organization of that stuff—the way the parts of the system are hooked up, their causal interactions. A fancier way of stating this is, “Consciousness is substrate-independent.” Functionalism serves biologists and engineers well when figuring out and mimicking nature, so why abrogate it when it comes to consciousness?

There are models that describe the mind as a number of functional boxes, with arrows going in and out and linking the boxes: one box for early vision, one for object recognition, one for working memory, and so on. These boxes are identified with specific processing stages in the brain. Adherents of this approach then point to one of them and declare that whenever information enters this box, it is magically endowed with phenomenal awareness.

In the last decade of his life, always willing to change his views in light of new evidence and ways of thinking, Francis warmed to information theory as the appropriate language for a theory of consciousness. Why? Well, in the absence of some special substance, such as Descartes’ thinking stuff that magically endows an organism with subjectivity, consciousness must arise out of causal interactions among hyperconnected brain cells. In this context, causal means that activity in neuron A, directly or indirectly, affects the likelihood of activity in neuron B in the immediate or more distant future.

On very rare occasions, the opposite can occur, when twins are born with conjoint skulls. In a recent case, there is credible evidence of two young girls whose brains are connected at the level of their thalami. Each appears to have access to what the other one sees. If true, this would be a remarkable comingling of brains and minds, far above and beyond the ecstatic celebration of orgasmic dissolution of Tristan’s and Isolde’s identities in Wagner’s eponymous opera.

Integrated information theory introduces a precise measure capturing the extent of consciousness called Φ, or phi (and pronounced “fi”). Expressed in bits, Φ quantifies the reduction of uncertainty that occurs in a system, above and beyond the information generated independently by its parts, when that system enters a particular state. (Remember, information is the reduction of uncertainty.) The parts—the modules—of the system account for as much nonintegrated, independent information as possible. Thus, if all of the individual chunks of the brain taken in isolation already account for much of the information, little further integration has occurred. Φ measures how much the network, in its current state, is synergistic, the extent to which the system is more than the sum of its parts. Thus, Φ can also be considered to be a measure of the holism of the network.