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William H. Calvin
The Cerebral Symphony
Seashore Reflections on the
Structure of Consciousness

Copyright ©1989 by William H. Calvin.

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The Random Road to Reason:
Off-line Trial and Error

Human problem solving, from the most blundering to the most insightful, involves nothing more than varying mixtures of trial and error and selectivity.
     the American computer scientist Herbert Simon, 1969

It takes two to invent anything. The one makes up combinations; the other one chooses, recognizes what he wishes and what is important to him in the mass of the things which the former has imparted to him. What we call genius is much less the work of the first one than the readiness of the second one to grasp the value of what has been laid before him and to choose it.
     the French poet and philosopher Paul Valéry (1871-1945)

Three centuries ago, Leibnitz propounded what might now be called the physiologist’s premise: "Everything that happens in man’s body is as mechanical as what happens in a watch."

      Does that apply to the mind too? Most people initially think it unlikely. But perhaps Spinoza suspected as much when he said, "The order and connection of ideas is the same as the order and connection of things." Earlier in the seventeenth century, Descartes was bold enough to conceive of a completely self-sufficing nervous mechanism able to perform complicated and apparently intelligent acts. Unfortunately, he still had a conceptual problem regarding followers and leaders, and so mired us even deeper in the dualistic body-and-soul metaphors of an earlier age.

      But by the late nineteenth century, Thomas Henry Huxley had explicitly prophesied that we would find a mechanical equivalent of consciousness — and this is manifestly the premise of most of my fellow neurophysiologists. Huxley reflected not only the biologists’ mood in the wake of Darwin’s revolution; the physicist Ernst Mach summarized in 1895 what many psychologists and philosophers had also begun to say, about how mental mechanisms could use the potent variation-and-selection combination:

[From] the teeming, swelling host of fancies which a free and high-flown imagination calls forth, suddenly that particular form arises to the light which harmonizes perfectly with the ruling idea, mood, or design. Then it is that, which has resulted slowly as the result of a gradual selection, [which then] appears as if it were the outcome of a deliberate act of creation. Thus are to be explained the statements of Newton, Mozart, Richard Wagner, and others, when they say that thoughts, melodies, and harmonies had poured in upon them, and that they had simply retained the right ones.

PURPOSE SEEMS SO DIFFERENT FROM CHANCE, but darwinism suggests that you might be able to have your cake and eat it too: chance plus selection, repeated for many rounds, can achieve much. Can darwinism achieve purposeful behavior, especially our planning-for-the-future behavior that has been such a powerful drive toward both civilization and ethics? Is it, indeed, the foundation of consciousness?

      That is, alas, not how traditional philosophers usually phrase the question. Friedrich Nietzsche said that the creative person works by instinct and checks himself by reason; Socrates had said that it was just the reverse order and so influenced Western thinking for a long time. Likely neither was right. Philosophers (and many scientists too) have a problem with randomness in any form. It is probably because so many think in oversimplified cause-and-effect terms and so, following Laplace, infer that things must be "determined" if there are physical laws. And thus random outcomes (horrors!) would result from random causes. People often yearn for certainty: T. E. Lawrence wrote, "Perhaps in determinism complete lies the perfect peace I have so longed for. Free-will, I’ve tried, and rejected it."

      We keep expecting human reasoning processes to be orderly — at least as orderly as those patrol cruises of an Eel Pond cormorant. To say that the height of human achievement usually contains a large dose of randomness is heresy, though people will readily admit to a role of randomness in preventing animals from "getting stuck." Remember Burdian’s Ass, who was equally hungry and thirsty? And who was poised halfway between food and water, and so starved? Or Hamlet’s inertia? But randomness has a far more important role than merely to act as a dice-tossing tiebreaker. A lowly bacterium would never get stuck like the apocryphal ass; indeed, bacteria find their way to food simply through selectively modifying randomness.

      The philosophers can perhaps be forgiven for being overly-impressed with thought as the highest of the higher cerebral functions, what’s left over if one stops looking for the seat of the soul. But it might be better to start with how animals make behavioral choices, like that sunbathing cormorant or the bookish skunk, and work our way up to logic. When looking at an E. coli bacterium swimming around, it is easier to see how randomness can buy food:

Organisms are problem-solvers seeking better conditions — even the lowest organism performs trial and error measurements with a distinct aim. This image brought to mind Howard Berg’s striking film of chemotaxic bacteria. He showed how a bacterium’s flagellar motor makes it run and tumble randomly until the bacterium senses a gradient of nutrient. The bacterium then reduces the frequency of tumbling and lengthens the runs towards a greater concentration of nutrient.
      the molecular biologist Max Perutz, 1986
The random element is the tumbling: The new direction of swimming bears little relationship to the previous path before the tumble. And so the cell’s path is a random walk unless something else happens. And the something else is simply suppressing the tumbling: When finding more and more food, the bacterium swims longer on its current straight path. This enables it to "home in" on the food source, perhaps a decaying morsel whose organic molecules are diffusing away into the water near the bottom of the pond (remember what a sugar cube looks like when dissolving in the bottom of a cup, how the sugar gradually spreads out).

      I can make a little working model of the bacterium in my computer, not unlike the way a child can build a model crane with an Erector Set. First I create some "food," particles scattered around about like a sugar cube dissolving in the bottom of a glass. Somewhere in the bottom of the glass, I place the bacterium, swimming in some random direction. I make the simulated cell tumble (reset its path to a new randomly chosen direction) about once a second, but suppress the tumble if the nutrient concentration is higher than a few seconds before. This shows the path taken with this suppression of randomness:

      And so the simulated cell homes in on the richest concentration of nutrient and usually comes back if it strays away. If I make it tumble every half second instead (or if I slow down its swimming rate by half, or make the food source richer), then it stays even closer to the center. When the food is gone, tumbling again causes the cell to seek a new source.

      Now most philosophers looking through a magnifying glass at that food-finding path would have ascribed intelligence to that purposeful performance of the little bacterium. At such a marginal magnification, it would seem to "home in" on the morsel. But the bacterium has no brain: It’s just a single cell with some inherited simple abilities such as swimming, tumbling, and sensing increasing yield. The properties of the environment are all-important too: That diffusion of decaying molecules from the morsel gives rise to a fall-off in nutrient concentration, the same way that the smell of baking bread gets weaker as one gets farther away from the oven.

      There are some people who hope to mine gold (and more useful metals) from the ocean floor — and they’re thinking of locating the rich spots by turning loose a lot of underwater robots that seek out the highest concentrations by exactly such a regulated random walk. But unlike a metal-hungry bacterium, they’ll shout "Eureka!" in some secret code that will be heard and deciphered by their owners, who will come and stake a claim on the ocean floor.

      One of the problems with prospecting robots is that they get fooled by weak lodes of gold while missing the rich one next door. But the randomness of the bacterium helps prevent sticking with false maxima: After all, the random walk will sometimes carry it far enough away from the weak source to sense the stronger source. Consider the simulated bacterium feeding on the weaker of a pair of morsels:

      If the run lengths are always short before taking another sniff, the bacterium can get fooled into sticking close to the minor source. But if we make it sniff every two seconds instead of every second, its uninterrupted swim will sometimes carry it far enough away to be captured by the major source. It may take a while before it escapes, but randomness does have its virtues: Now the simulated bacterium would seem, to those philosophers peering through the magnifying glass, to have purposefully approached the two morsels and decided which was bigger! And it wouldn’t have been easy to persuade the philosophers that randomness did the trick, because they were accustomed to thinking of randomness as the exact opposite of purpose.

[There are now movies on the web of bacteria, e.g., http://www.comet.chv.va.us/quill/animabug.html-ssi]

      Now the owner of those prospecting robots has goals that are different from those of the randomly walking bacterium. For the E. coli cell, one has the "a bird in the hand is worth two in the bush" phenomenon: It may prefer to refuel rather than search out the all-time champion of rich foods. The robot master may wish reassurance that a region has been reliably covered for sources richer than a minimal concentration, so that he can call home all the robots and move the whole operation to Hawaii. Random walks will sometime miss substantial patches that are surrounded by distracting small morsels. Of course, when one can install a microcomputer inside a robot, one is tempted to design search strategies that are more sophisticated than the bacterium’s "cheap and good enough" scheme.

      It might be easier to train some cormorants so that they think gold is food; after all, dolphins have been persuaded to find lost torpedoes in exchange for frozen fish, and people have been persuaded to dig ditches in exchange for money that can be exchanged elsewhere for frozen fish. But maybe cormorants are too smart to fall for that scheme.

NO ONE NEEDS A WEATHER VANE around here to tell which direction the wind is blowing: All of the sunning cormorants in Eel Pond turn to face into the wind. The other morning was dead calm, the pond like a mirror, reflecting every detail of the sailboat rigging. And so the cormorants and boats got a little disorganized, without any wind to orient them. But let a breeze come up and they will fall into formation; let the breeze switch around and, like a gaggle of geese, they’ll follow it en masse.

      Today, you can see the breeze: The ivy facade of the colonial-style oceanography building down on Water Street is being rippled by gusts. There are waves flowing from one end of the building to the other. Sometimes two or three ripples can be seen at the same time, all propagating along the ivy blanket. And I used to think of wind waves as being whitecapped horizontal waves: these waves stand up and move sideways.

PEOPLE ARE FANCIER THAN BACTERIA, the philosophers might justly reply when confronted with the purposeful appearance of food-finding that is based on suppressed randomness. Common sense says that human behaviors couldn’t be based on something so "irrational" — except, perhaps, for a drunkard’s random walk?

      A wave of déjà vu sweeps over me each time I hear randomness sold short again. The same arguments were used against evolutionary thinking a century ago in the wake of Darwin: Few people’s imaginations could see how random walks could yield the optics of the eye or the circuitry of the brain. A century later, newcomers still make the same mistake — until they study the anatomy long enough to see all those hallmarks of variation and selection. And I suspect we’re repeating this history by selling short the power of randomness for producing the interesting things that minds do.

      Of course, randomness by itself cannot produce such elaborate results, for all the usual reasons having to do with a roomful of monkeys typing a page of Shakespeare — it would take more time than the universe has existed (15 billion years) to arrive at that particular combination of words. We’re always talking about randomness plus selective retention of some sort, and repeated cycles of this back-and-forth two-step dance serving to gradually shape up the unlikely. Richard Dawkins nicely illustrates this in The Blind Watchmaker by a little computer program that shapes up a random set of words into a near-mimick of a line from Shakespeare.

      It’s the combination of randomness and selection that is so powerful, not just selection, not just randomness. They are inseparable sides of the same coin (well, you can separate them — as when selection acts on a highly inbred gene pool with little combinatorial variability remaining — but they don’t go anywhere). The foraging bacterium selectively retains those paths that seem successful, simply by postponing the next bout of random tumbling. Evolution, however, always involves a great number of individuals and many generations, making natural selection’s cumulative editing of randomness harder to demonstrate within the observer’s own lifetime. But it’s much the same story.

      Biological evolution usually involves variations on some theme (short or tall, fat or thin, naked or hairy, slowly or rapidly maturing). The environment "selects" the most successful and, provided that some tendency toward the theme is inheritable, their enhanced reproduction means that the average body style shifts toward the most suitable, simply because fewer of the less favorable body styles grow up to become parents themselves.

      Of course, there are many cultural innovations which don’t appear to be such variations on a theme: logical reasoning and Eureka! discoveries, for example. But as with "brainstorming" generating lots of variants (but preventing premature closure, selecting too soon), maybe each person’s brain uses the same technique, but subconsciously, so we’re not aware of randomly generating a lot of nonsensical possibilities before we then select a reasonable one.


If man was to think beyond what the senses had directly given him, he must first throw some wild guess-work into the air, and then, by comparing it bit by bit with nature, improve and shape it into a truth.
      the English geologist William Smith, 1817

A blind-variation-and-selective-retention process is fundamental to all inductive achievements, to all genuine increases in knowledge, to all increases in fit of system to environment.
      the American psychologist Donald T. Campbell, 1974

EXPERIENCE CAN BE CONSIDERED the elimination of bad guesses, but a guess can be much more elaborate than merely the bacterium’s tumbling, the random choice of a new direction. It doesn’t take a brain to choose a random direction — indeed, the E. coli isn’t even a specialized cell like a nerve cell, much less a brain. But with a little more machinery, a cell can engage in more specialized locomotion, such as the way that a paramecium backs up when it bumps into an inedible obstacle, then turns to zoom off in a new random direction. And with a collection of nerve cells called a nerve net or a ganglion, behavior gets even fancier. With the head ganglion arrangement that we call a brain, the random elements can often be carried out inside the neural machinery itself — and in advance, so that the expressed behavior no longer looks random but rather purposeful, even insightful or logical.

      Thanks to memory, the brain can carry around a rough representation of the environment: whether hot/cold is good/bad, whether bright lights are a good thing to approach or avoid, whether that particular item of the diet made one sick the last time it was eaten, etc. Of the many possible plans for one’s next movement, some will evoke bad memories of what happened the last time something similar was attempted. Others will evoke fond memories of a feast or a snug nesting place. Depending on other factors such as hunger or reproductive drives, some plans will rate higher than others. Fancier organisms can solve fancier problems and thus utilize new resources — which is probably how they evolved to be fancier in the first place.

      In particular, some animals have gotten to be so fancy that they seem to simulate extensively a course of action before taking even a tentative first step. While the chess master who looks a half-dozen moves ahead and the army general who attempts bluff and counterbluff are extreme examples of how to make and compare alternative plans, even our pet cat seems to contemplate choices. One occasionally sees an animal seemingly plan several steps ahead, even engage in deception:

One evening I was sitting in a chair at my home, the only chair my dog is allowed to sleep in. The dog was lying in front of me, whimpering. She was getting nowhere in her trying to "convince" me to give up the chair to her.... She stood up, and went to the front door where I could still easily see her. She scratched the door, giving me the impression that she had given up trying to get the chair and had decided to go out. However, as soon as I reached the door to let her out, she ran back across the room and climbed into her chair, the chair she had "forced" me to leave.
      Peter Ashley, 1981
While "aren’t they clever" animal stories abound, most of them have potentially simpler explanations (e.g., the dog didn’t plan but merely saw the empty chair while at the door — and its desire to sleep then exceeded its desire to explore outdoors). Still, I suspect that humans merely have substantially greater (what scientists like to call "order-of-magnitude greater," meaning about tenfold) abilities to mentally compute future alternatives, not that humans are unique in having foresight.

      Indeed, looking ahead is so powerful a technique that the big problem is why don’t we see more extensive examples of it in the animal kingdom. Jacob Bronowski put it very well in his 1967 Silliman Lecture at Yale:

[None of the termite-fishing chimps] spends the evening going round and tearing off a nice tidy supply of a dozen probes for tomorrow. Foresight is so obviously of great evolutionary advantage that one would say, "Why haven’t all animals used it and come up with it?" But the fact is that obviously it is a very strange accident. And I guess as human beings we must all pray that it will not strike any other species.
The combination of biological and cultural evolution has happily provided us with foresight, an ability to look ahead and assess the probable consequences of our actions and so choose the better course without actually traveling the others and then comparing. Planning ahead, taking account of the nonroutine, is a key element of what is called consciousness, as Bronowski observed:
[Humans’ unique abilities] to imagine, to make plans... are generally included in the catchall phrase "free will." What we really mean by free will, of course, is the visualizing of alternatives and making a choice between them. In my view, which not everyone shares, the central problem of human consciousness depends on this ability to imagine....
And that in turn raises the question of why humans don’t plan ahead more than we do, given our extensive abilities and how handsomely they pay off.


I’VE ALWAYS WANTED A SAILBOAT like the one now sailing out of Eel Pond beneath the raised drawbridge, but I flunked the ownership test. There is a special test for prospective boat owners, designed to weed out those who aren’t temperamentally suited to the rigors of boat ownership.

      First you figure out an annual budget; divide the cost of your desired boat by about six, and that is your capital cost per year. Add moorage, then an equivalent amount for insurance and repairs. Add the cost of the annual renovations to the interior. Add new sails, one each year, on the assumption that they are constructed of spun gold. Sum up and add 20 percent for good measure; this gives your annual budget.

      Then estimate about how many times each year you’ll take the boat out, and for how many hours, to give you the hours of pleasure you’ll maximally achieve; deduct the hours you’ll spend arranging repairs and writing checks. If the sum is greater than zero, correct for over-optimism, especially if your schedule or the local weather is more fickle than average.

      To complete this first stage of the boater’s qualification test, you must not be standing up. Sit down in a comfortable chair and divide these hours into the annual cost. This gives you the actual cost per running hour.

      If you pass this stage of the test, you are allowed to go out and buy the most comfortable life jacket you can find, along with rain gear and a small camp stool. You must also stop at the bank and get a nice stack of twenty-dollar bills, amounting to the cost of a weekend’s running time. Be sure not to ask for new, crisp bills.

      The next morning, you arise before dawn and make yourself a day’s supply of sandwiches and a Thermos of coffee. Then you place them and your camp stool in your shower stall, don your life jacket and rain gear, pocket a packet of twenty-dollar bills representing the day’s running cost, sit down on the stool, and turn on the shower. You adjust it to the temperature of the local rain less 20°, to compensate for the wind chill factor (unless your shower stall is located in a wind tunnel).

      You sit there all day, slowly tearing up twenty-dollar bills and stuffing the soggy scraps down the drain.

      Those who pass this second stage of the test are allowed another day in the shower stall with the water turned off and a suntanning lamp substituted. The twenty-dollar bills are somewhat harder to stuff down the drain when not soggy, so you are allowed some bilge water to soften them up. Your lunch will get soggy whether it is raining or not, so the water underfoot will aid in realistically simulating conditions at sea. Upon successful completion of stage three, you are finally allowed to buy a boat, if still interested.

      This test is quite safe, involving none of the usual hazards of falling overboard, or getting hit by the boom when the wind shifts unexpectedly, or becoming stranded on a sandbar, or being snagged by a fishhook. The mental hazards of this test are considerable, and I hereby disclaim all responsibility for what might happen to you, but they are surely no worse than actual boat ownership.

      Only prospective boat owners who pass this test are truly suited to the rigorous life of the sailor. The number of boats around Vineyard Sound presumably attest to the number of people who find the shower-stall test invigorating — the alternative being that boat owners don’t think ahead. At least, not any more than prospective parents volunteer to spend a weekend caring for the neighbor’s squalling infant, giving the parents a respite and "test driving" before they acquire one themselves.

PLANNING AHEAD is thought to have something to do with our oversized frontal lobes, as injuries there sometimes disrupt abilities to change strategies. While frontal-lobe damage may occur from tumors and strokes, perhaps the most common cause (and certainly the most easily preventable) is a head injury due to a car accident. Even if the skull isn’t fractured by the impact, the soft brain rattles around inside its bony case and gets bruised.

      Seat-belt usage shows an interesting "a little knowledge is a dangerous thing" aspect of looking ahead: Your conclusion depends on how far ahead you look. If you only look ahead to the grocery store, then of course the chance of anything happening is very small. Having succeeded many times in making such trips without incident, everyone except beginners tends to be very aware of the low probability of immediate injury — and some use it to rationalize ignoring "do this, it’s good for you" parental-sounding advice about wearing seat belts.

      But most people are not capable of looking years ahead and drawing valid inferences from the accident records. Those who are so skilled, however, have discovered that you have a one-in-three chance of being in a serious injury car accident sometime during your life. That arithmetic works out to "someone in your family is likely to be in a bad accident."

      The trouble is: You don’t know when it’s going to happen. It’s as likely to happen on a short trip as on a highway trip. And so, the only solution that I know, until we reform drivers and redesign cars, is routine precautions: refusing to ride in the front seat of taxicabs with protruding fare meters, pencils, and other things you wouldn’t want your head to collide with. Foremost, however, is making a habit of always buckling the seat belt and pulling it tight, just as you make a habit out of brushing your teeth every night. That way, you’ll be wearing the seat belt some year when something does unexpectedly happen to you. A seat belt reduces death and injury by about half, so it seems an exceedingly rational choice. And quite the opposite conclusion than the one you form looking ahead only a little. It thus becomes a particularly dramatic "use it or lose it" principle: Failure to use one’s frontal lobes can result in the loss of them, given the way in which they are the "leading edge" of one’s forward trajectory in a collision.

TO POSTULATE MENTAL MACHINERY for simulating the future is one thing, but to demonstrate its properties is another. In particular, we want to know on what occasions we use it and when we don’t. We want to know how it develops, both in children (they start enjoying fantasy and planning "tea parties" by the age of three) and in evolutionary terms (certainly by the apes, but what about monkeys?). And we want to know how planning ahead evolved via good old darwinian advantages.

      But as the seat-belt rationalizations demonstrate, evolving foresight may not be a straightforward problem: A little foresight can even be a disadvantage. Furthermore, the relative lack of other foresightful animals suggests that this is a rare route we’re seeking to uncover, not a commonplace one. So the evolution of foresight via the usual more-is-better route starts looking pretty slow and uncertain.

      Yet something has got to explain our consciousness, and if halfway versions of foresight seem unlikely to bootstrap it up to its present level, perhaps there is some missing scaffolding. Arches cannot stand until complete; during their construction, something else has to hold them up temporarily. Is there some missing scaffolding where foresight is concerned? Perhaps planning evolved via good old darwinian sidesteps: as Charles Darwin noted, sometimes new functions emerge from old machinery, a conversion of function.

      Scaffolding and new uses for old anatomy: Can either help explain why we’re so good at planning ahead, or seeing ourselves as the narrator of our life’s story?

I have in my possession photostatic copies of several pages of Beethoven’s sketches for the last movement of his "Hammerklavier Sonata"; the sketches show him carefully modeling, then testing in systematic and apparently cold-blooded fashion, the theme of the fugue. Where, one might ask, is the inspiration here? Yet if the word has any meaning at all, it is certainly appropriate to this movement, with its irresistible and titanic energy of expression, already present in the theme. The inspiration takes the form, however, not of a sudden flash of music, but of a clearly-envisaged impulse toward a certain goal for which the composer was obligated to strive. When this perfection was attained, however, there could have been no hesitation — rather a flash of recognition that this was exactly what he wanted.
     the American composer and conductor Roger Sessions, 1941

Many students of animal behavior have become so fascinated with its directedness, with the question "What for?" or "Toward what end?" that they have quite forgotten to ask about its causal explanation. Yet the great question... "How?" [is] quite as fascinating as the question "What for?" — only they fascinate a different kind of scientist. If wonder at the directedness of life is typical of the field student of nature, the quest for understanding of causation is typical of the laboratory worker. It is a regrettable symptom of the limitations inherent to the human mind that very few scientists are able to keep both questions in mind simultaneously.
      the Austrian ethologist Konrad Lorenz, 1960

The Cerebral Symphony (Bantam 1989) is my book on animal and human consciousness, using the setting of the Marine Biological Labs and Cape Cod. AVAILABILITY is limited.
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