Rethinking Consciousness: A Scientific Theory of Subjective Experience

by Michael S.A. Graziano

“stream of consciousness,” the constantly changing, kaleidoscopic contents of the mind. It’s that riot of stuff in your head that James Joyce famously captured in his 1922 novel Ulysses.

Joyce meticulously recorded the ever-changing sight and sound and touch of the world, the taste and smell, the memories of the recent and distant past boiling up, a running internal dialogue,

Consciousness can’t be just the information inside us, because we’re conscious of only a small amount of the huge pool of information in the brain at any one time.

the rise of computer technology has revealed the distinction between the content of consciousness, which is increasingly well understood at an engineering level, and the act of being conscious of it.

The mechanism in the eye of a crab is arguably the simplest and most fundamental example—the model A case—of attention. Signals compete with each other, the winning signals are boosted at the expense of the losing signals, and those winning signals can then go on to influence the animal’s movements. That is the computational essence of attention.

Octopuses, squid, and cuttlefish are true aliens with respect to us.15 No other intelligent animal is as far from us on the tree of life. They show us that big-brained smartness is not a one-off event, because it evolved independently at least twice—first among the vertebrates and then again among the invertebrates.

If you film people hammering and track their movements in detail, you find that the shoulder rotates in variable ways, the elbow wobbles unreliably, the wrist movement is a little different every time, and yet the head of the hammer

may seem far-fetched to suppose that a zebra “understands” the consciousness of another animal, but it seems that way only because we humans think of consciousness as a noble characteristic, special to us and rich with cultural associations. Zebras shouldn’t have the poetry or complexity for it. But that’s just our ego talking. I suggest that consciousness is an ancient part of theory of mind; it is a simple, efficient model that is used to make predictions about the behavior of animals and is likely to have evolved long before humans.

popular idea that consciousness emerges from complexity. Because we have the most complex brains of all animals, we must also have the most vivid consciousness. Yet of all the mental talents that we humans like to brag about—math, language, tool use, and so on—consciousness may be one of the most primitive and least special to us.

call it substance C. The substance is invisible. It cannot be directly observed. It doesn’t block or reflect light. It’s generated inside Kevin and flows outward. It has a bias toward flowing out of the eyes along straight lines, although it does not necessarily take that path, since it can also sometimes reach out in nonvisual directions. It makes contact with specific objects in the environment. It can be partitioned among objects, but only in a competitive manner, such that as it becomes focused more on one object, it’s relatively withdrawn from others. Like water from a hose, the more Kevin sprays at one object, the less he has to spare for another. Substance C acts a lot like a classical fluid.10 It flows from a source. Its total volume is roughly conserved—in the sense that more of it flowing here means less of it flowing there. It’s also slightly viscous—it changes direction with a certain degree of sluggishness. At the same time that it acts like an invisible, viscous fluid, it also has an energy-like or will-like property in the sense that it empowers the agent. It does not directly galvanize Kevin to act, nor does it determine the specific action. Instead, its presence acts like an energizing field that powers Kevin to make a behavioral choice.

Substance C is a simplified, model version of cortical attention. It’s an attention schema.

In the ninth century AD, the Arab scientist Ibn al-Haytham finally worked out the correct laws of optics and declared that extramission was wrong. Light enters the eye in straight lines to form an image. Despite that definitive scientific answer, a folk belief in eye beams persisted. A thousand years after al-Haytham, a belief in an “evil eye” is still common across many cultures, along with a lucrative trade in amulets that can protect you from it.13 In our culture, Superman has X-ray vision, which somehow shoots out of his eyeballs and burns things. Almost everyone has had the spooky feeling of being stared at from behind, as if a beam of energy is touching the back of your neck.

Rather than dismissing consciousness, the theory places it at the center of our abilities. It is an ancient, highly simplified, internal model, honed by evolution to serve two main useful functions, as I have described over the last several chapters. Its first function may have been as a self model, to monitor, make predictions about, and help control one’s own attention. The second function may have been as a catalyst for social cognition, allowing us to model the attentional states of others and thus predict their behavior.

Similarly, when studying consciousness, whether the test subject is aware of the left-eye image or the right-eye image, she’s equally aware of an image in both cases. Any brain region that is computing information about the presence of consciousness should be equally active in both cases. It should not switch on and off depending on whether one or the other image is dominant. The experiment would specifically miss areas of the brain computing the construct of consciousness.

To give another example of an imperfect model built deep within us, consider how we see the color white. The visual system builds a model of white as brightness in the absence of any contaminating colors. That model evolved over millions of years and is shared across many species of animal.

We could say that the “hard problem” of the color white is, What is the special physical process that purifies white light of all its contaminants? The corresponding meta-problem is, Why do we even think this hard problem exists? Why do we think that white light is purified? We now know the answer to the meta-problem—the brain constructs a simple, pragmatic, but imperfect model—and with that, we also know that the hard problem doesn’t need to be solved.

Attention is a layered set of mechanisms—a data-handling method—whereas consciousness is an inner experience that we claim to have. Attention is something the brain does; consciousness is something the brain says it has.

IN 1950, THE mathematician Alan Turing proposed a way to test if a machine can think.3 The test involves three people playing a game: a deceiver, a truth-teller, and a guesser. The three are seated in separate rooms and can communicate only through writing, to avoid any unintended personal clues passing between them.

The job of the guesser is to figure out which is which. The job of the truth-teller is to faithfully convey the correct answer to the guesser. The job of the deceiver is to confuse the guesser and convey the wrong answer.

The next step is to replace the human deceiver with a machine deceiver. If the machine can win the game as often as a human, then the machine can think like a human. That’s the original Turing test.

The modern version focuses on consciousness instead of social cognition. To tell if a machine is conscious, you should simply have a conversation with it. If you can’t tell whether it’s a machine or a person, then it passes.

To the extent that the James-Lange theory is true, it raises some interesting questions about machine emotion. Would an android need a stomach, sweat glands, and a heart to feel emotions the same way that people do? If the machine could never know the taste of food or the feel of digestion, never have adrenaline rushing through its body priming it to fight or flee, could it have real emotions? I suspect it can have processes very similar, though probably not identical, to human emotion. We might have to give it sensors throughout its body to ground its emotions in a physical substrate.

For example, nobody predicted the social revolution that was caused by cell phones. At first we thought they would be an amazing convenience, like microwave ovens, but then they turned into the third hemisphere of the human brain.

Your uploaded mind would be lucky to last 10 years before it was no longer compatible with the newest operating system. We’d be throwing out Grandma like we threw out WordStar,

What would be the rights accorded to simulated and biological minds?

To get the technology to work, somebody’s simulation is going to be put through existential torture, over and over, fine-tuning the method.

what happens to the sanctity of life and of individuality when you’ve made three copies of yourself already?

humanity will overcome war and disease and spread out over the galaxy as a peaceful, scientifically curious species in warp-drive starships. There we’ll encounter and peacefully blow to smithereens various troublesome aliens.

The color of the apple, for example, is partly a construct of the brain. In reality, the apple has a reflectance spectrum, not a color. The eye and the brain simplify that spectrum and assign a color. Color is a caricature, a quick-and-dirty proxy.

S. J. Blackmore, “Consciousness in Meme Machines,” Journal of Consciousness Studies 10 (2003): 19–30.