It's a Jungle in There: How Competition and Cooperation in the Brain Shape the Mind (34 page)

This is a perfectly fine, workaday definition, though if this statement is thought to explain what consciousness is, I confess I’d like to know more. I know that when I’m conscious, I’m thinking not just about what I’m
doing, but also what I might be doing in other circumstances. Being told by various philosophers and psychologists that those experiences are what consciousness is tells me nothing I don’t already know. Consciousness is clearly some emergent feature of neural activity, but saying that isn’t an explanation, no matter how alluring the emergent-feature notion might be. For example, consciousness might be likened to murmuration, the ever-changing form of a flock of birds winging its way through the sky. Starlings best illustrate this kind of “swarm intelligence.”
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The form of the flock changes dramatically and can do so in an instant. The form is evident only from afar, however. It’s an emergent feature of the birds flying together, and it’s made possible by the fact that each bird responds to its local conditions.
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No overseer is needed to shape the flock. The shape changes dynamically via self-organization.

Analogizing consciousness to murmuration makes for lovely images but hardly explains what the emergent feature of consciousness is, or what critically distinguishes consciousness from other emergent features of neural activity, like the factor—whatever it is—that distinguishes the brain activity of people who are conscious from the brain activity of people who aren’t.
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Does the jungle principle explain consciousness? Frankly, I don’t think so, or at least not in a way I’m aware of. Might it help explain it someday? I’d be delighted if it did, but this is just wishful thinking on my part.

Likewise for qualia, otherwise known as qualities of experience. Examples of qualia are the smell of a rose, the sight of a sunset, or the sound of a cello. These are experiences that are essentially impossible to put into words.

What accounts for the distinct aspects of experience? What makes a smell a smell, a sight a sight, a sound a sound? An early idea was that the nervous system has “specific nerve energies” for different sensory modalities. According to this hypothesis, nerve impulses from the nose, eye, or ear carry specific information about the modality they’re conveying. Smell-related nerves have different signals than sight-related signals. Similarly, sound-related nerves have different signals than taste-related signals, and so on. That, anyway, was the hypothesis.

Johannes Müller, an eighteenth-century German physiologist who proposed this idea, noted that by pressing gently on his closed eye, he saw flashes.
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Müller inferred from this observation that something about the nerve signals from his eye carried the quality of sight. It didn’t matter, according to Müller, whether the energy that triggered the eye’s neural signals was optical or mechanical. What mattered was that the source of the signals was the eye. By this way of thinking, something about nerve signals from the eye
carries the quality of sight. Analogously, something about nerve signals from the ear carries the quality of sound, something about nerve signals from the skin carries the quality of touch, and so on.

Müller’s inference was reasonable even if it failed to specify what the specific nerve energies might be or what about them signified the qualities they do. Later research called the specific-nerve notion into question, however. Edgar Adrian, a British physiologist who won the Nobel Prize in Physiology or Medicine in 1932 (sharing it with Charles Sherrington) found that nerve signals were the same throughout the nervous system. According to Adrian’s research, nerve signals do
not
differ depending on which sensory pathway they’re in. This meant that phenomenological differences between the senses arise from central rather than peripheral sources. What makes smells “smelly” or touches “touchy” depends on where sensory inputs land within the brain, not where the inputs launch in the periphery.

How can this idea be tested? An experiment by the American physiologist Roger Sperry lent support to the alternative “central-site” hypothesis—the idea that the place in the brain where inputs are registers determines experience. Sperry reasoned that if the source of experiential differences is where sensory inputs are registered in the brain, then altering where those sensory inputs arrive within the brain should alter the experiences they produce. Sperry worked with frogs, choosing them as subjects because the optic nerve of the frog’s eye projects to the frog’s opposite brain hemisphere. Thus, for a frog, the left eye’s optic nerve projects to the right hemisphere and the right eye’s optic nerve projects to the left hemisphere. This gave Sperry a logical opening to the problem of what matters more—where in the periphery sensory signals originate or where in the brain sensory signals go.

Sperry cut the optic nerves of a frog’s two eyes and redirected the nerves to the same side of the brain as the eyes from which they projected. So following the surgery, the left eye’s optic nerve projected to the left hemisphere, and vice versa (not the usual arrangement). The result was that the frogs carried out movements that were opposite to the ones they normally performed. If an object approached from the left, which normally caused the animal to move to the right, that same looming object now caused the frog to move to the left, toward the object, not away from it, and vice versa for an object approaching from the right. This outcome showed that it was where in the brain the sensory input was received that defined how the input was interpreted.
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What is it about the left hemisphere of the frog’s brain that caused it to interpret input one way or another? All you need to say is that neural connections exist between the relevant brain sites and the sites responsible for
producing leftward or rightward movements. If those connections are sufficiently strong, it doesn’t matter whether the original activation comes from the left eye or right. Admittedly, it’s a jump to say that if a frog’s brain site causes one or another leg to move, the frog has different phenomenological experiences. You can’t ask a frog what it’s experiencing, or if you do, the conversation will be decidedly lopsided. Still, the frog’s overt behavior gives a clue to the nature of its experience.

There is a finding that bears more directly on the nature of experience following neural transplantation. When neural transplantation occurs in people, albeit as a result of natural rather than laboratory experiments, people’s experiences depend on where sensory inputs arrive in the brain, not where the sensory inputs originate in the periphery, just as Sperry concluded.

A relevant study was described earlier in this book. It concerned amputation. Recall from
Chapter 3
that a man whose arm had been amputated nevertheless felt his fingers being touched when his face was palpated. The psychologist who discovered this—or at least made the finding public, as the amputee knew it all along—expected this result because of his knowledge of neural plasticity. Sensory signals from the face, the psychologist surmised, would infiltrate the finger region when no sensory signals came from the fingers themselves. With the finger inputs now dormant, they would be less able to fend off onslaughts from facial factions. The finger region of the brain, receiving inputs from a site whose true address in the periphery was unknown to the brain’s finger region, sent signals to other centers that would translate the signals into finger feelings. Unlike Sperry’s frogs, whose only means of communicating what was felt was by moving, the man with the amputated arm could say what he felt. What he said went along with the hypothesis that feeling was determined by where in the brain inputs were received, not by where the sensory signals originated on the body surface.

Based on these considerations, you can say that qualia depend on central rather than peripheral factors. Still, you’re left with the mystery of how phenomenology and phenomenological differences arise in the first place. If you turn to one of the brightest lights in cognitive psychology to find an answer to this riddle, the result is a bit disappointing. Steven Pinker, the bright light to whom I refer, wrote the following sentence on this topic: “The problem is hard because no one knows what a solution might look like.”
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Like Steven Pinker, I’m a member of the loosely knit team of cognitive psychologists who have no idea what the form of the solution might be to the problems of what consciousness is and, relatedly, what qualia are. It’s not a fact I’m proud of. In the context of the jungle principle, I could
suggest that different qualities are experienced because different kinds of inner agents are activated. But that’s no explanation; it merely dresses up the problem.

A couple of remarks may prove useful, however. First, despite the fact that there are different qualities of perceptual experience, these forms of perceptual experience interact. Inter-sensory interactions are replete. For example, the place where you hear a puppet’s voice is at the puppet, not at the ventriloquist.
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How many flashes you see when a single prolonged light is shown depends on how many beeps sound when the light is presented.
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And what you hear someone say when you watch him or her in a video depends on what his or her lips are doing. If the lips say one thing and the sound says something else, you hear a blend of the two.
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Phenomena like these suggest that different forms of representation commune. Inputs from different sorts of receptors don’t go off to their own separate worlds. Rather, they come together in ways that yield integrated experience.

The second potentially useful remark is that because qualia are emergent features of neural interactions, they can be likened, albeit loosely, to chemical phenomena. When chemicals mix, all sorts of unexpected things happen. The mixture can change color, it can form crystals, it can produce explosions, and so on. Characterizing the phenomena of chemical reactions is what chemists get paid to do. They’re hired because the phenomena they uncover can have important applications. For example, finding that sulfur and rubber can jointly produce an extremely durable material capable of supporting automobiles can make for a Goodyear.
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The parallel to neurally based phenomena should be obvious, and indeed the parallel has been noticed by some influential cognitive psychologists. William Estes, a founder of mathematical psychology and a winner of the National Medal of Science in 1997, published an article in 1960 called “Learning Theory and the New ‘Mental Chemistry.’”
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John Anderson, a cognitive psychologist at Carnegie-Mellon University and the current editor of the journal
Psychological Review
, co-authored a book called
The Atomic Components of Thought
.
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These two cognitive psychologists, like all the other cognitive psychologists I know, believe in
associations
among ideas.
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If mental associations are like molecular bonds, then much as molecular bonds arranged in different ways can produce different emergent phenomena, so might mental links. What’s not clear, though, is how to get from links to awareness. How the brain produces the mental equivalents of color changes, crystal formations, and explosions is as yet unknown. When we can explain such emergent phenomena, we psychologists will be able to say that, like the discoverer of
hard rubber, we had a good year. For now, all we can say, or all I can say, on this matter is that I stand before you intellectually naked.

Chances are you weren’t tumescent while reading this book. If you were, it wasn’t from the book itself. The word “tumescent” means “swollen or showing signs of swelling, usually as a result of a buildup of blood or water within body tissues.”
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When I suggest you weren’t tumescent, I mean you probably didn’t feel your genitals gorge with blood when you read this volume. Had this book been X-rated, the result might have been different.

Why do I bring up sex? Psychology has gotten very sexy lately, though, truth be told, it always has been. Freud said long ago that beneath the thin veneer of civilization, we harbor seething passions. To control those passions, he said, we have two levels of control—the ego and, on top of that, the superego.

Regardless of what drives you, it’s likely that what you enjoy is consistent with the successful transmission of your genes. That, anyway, is the anthem of evolutionary psychology, a field I’ve not talked about much here, though it’s always been in the background. I’ll now bring it to the fore to compare and contrast it to the approach I’ve kept front and center.

Unlike cognitive psychologists, evolutionary psychologists often study very “juicy” subjects. For example, one group of evolutionary psychologists studied striptease dancers. The evolutionary psychologists found that the tips the strippers earned depended on when the performers danced relative to their menstrual cycles.
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When the strippers were ovulating (when they were most fertile), the tips they got were large, but when the strippers were not ovulating, the tips they got were small. The dancers didn’t stop flirting with the customers during their less fertile times. Teasing, after all, was their stock and trade. Instead, something about them—how lustrous their skin, how lilting their voice—caused customers to be more appreciative when the dancers happened to be physiologically primed for conception than when the dancers were less fecund.

A finding like this provides fuel for evolutionary psychologists, who take their cue, as do I, from Darwin. For evolutionary psychologists, the primary concern is the impact of the evolutionary past on present-day psychology. For me, by contrast, the primary concern is the impact of the
individual’s
past on the organization of his or her mind in the here-and-now. For evolutionary psychologists, if strippers gyrate as gamely as they can but to less effect when
they’re infertile, that makes sense from an evolutionary perspective. Women who succeed in seducing men should, one would think, be more likely to produce offspring than women who are less successful. Similarly and shifting to a different domain, if you’re spooked by snakes, that may be because it was adaptive for your ancestors to be scared of serpents.