How the Brain Works

by GEORGE R. HARRISON

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THE human brain is a highly specialized device for processing information, produced by nature after nearly a billion years of experimenting with electrochemical signaling systems. In evolution information is very important, for it aids in the promotion of order. On the level of the atom, in fact, order and information are almost identical. In a disorderly or chaotic universe, one that operated by chance alone, the term information would be meaningless.

All the phenomena of our universe are expressions of a remarkable process of transferring order through the building up of patterns. An atom is an orderly pattern of protons, neutrons, and electrons. A molecule is an orderly pattern of atoms. A sponge, a cherry, or a man is an orderly pattern of cells, which in turn are orderly arrangements of molecules. A nest of termites or a nation brings increased order to the behavior of individuals.

Such orderly patterns are produced and maintained in nature by the transfer of information. In the community which is an atom, the latest news is passed around through the pushes and pulls of electric, magnetic, and gravitational forces. In the body of a higher animal, hormone messengers sent via the blood stream tell the adrenal cortex and other glands the desires of the pituitary. Empires such as that of Rome were held together by roads along which runners carried the messages of government; the United Nations or some successor pattern will attain its ends more quickly and completely as a result of the improved communications provided by such devices as television, radio, teleprinting, and automatic translating machines.

The order pattern which is the brain of man has already resulted in two basic new inventions by nature, two jumps forward which have greatly accelerated the production of new patterns of order. In an era in which improvements in the educative process are of great concern to us all, the genesis of the brain is worth retracing.

Far back in evolution, when certain kinds of cells found advantage in living together in the chemically social groups we call animal bodies, communications systems among the cells had to be developed if a colony was to behave as a unit. As a result of much changing and selecting, certain types of cells, the neurons, came to behave as tiny batteries which could pass pulses of electricity from one to another like a molecular bucket-brigade. When these pulses of current reached a muscle cell, they caused it to contract, and thus produced motion of the whole cell colony. Gradually such nerve paths were developed throughout each animal body to serve as communication lines from sensory pickup cells to the muscle cells. Eventually the signaling systems became so complex that central switching stations had to be developed, and one of these became our brain.

Biologists can now determine fairly well the stage of evolution at which each of the several dozen senses possessed by man began to be differentiated from more elementary signaling devices. Sea anemones have elementary nervous systems with which they can feel contact and respond to it. Jellyfish have the beginnings of eyes, special spots more sensitive to light than their surrounding cells.

One cannot fail to be impressed, in tracing the evolution of the various senses, by the evidence that each new window of awareness to the world was not opened suddenly for any creature as an outright gift, but rather had to be developed slowly. Each new molecular pattern to which mutations gave rise was tested by use over countless generations, and selected for survival by its fitness. Sight did not dawn in any dark and misty world when God first said “Let there be light,”for light was for aeons merely energy t hat kept the creatures of the world alive. Not until much later did it become a carrier of information from the outside world into each creature that could see.

We take our senses overly for granted. We are accustomed to feeling almost anywhere in our bodies such sensations as pressure and pain and heat and cold; but we are amazed at the thought of smelling or tasting with such parts of the skin as a shoulder or a forehead. Yet many fishes and frogs do exactly the equivalent of this. Sharks can be attracted from miles away by a piece of meat dragged behind a boat, and are found to have sensory pickups scattered all over their bodies, with which they do something intermediate between tasting and smelling. We taste with our mouths alone, and smell only with our noses, merely because the sensitive cells for taste and smell, like the pickups for hearing and sight, have in all higher animals become concentrated in small areas. Not so t hose for temperature and pressure, for some 200,000 living thermometer cells are scattered over our bodies, together with about half a million pressuresensing cells. Scattered throughout most regions of our flesh are three or four million sets of receptor cells that give the signals which our brains interpret as pain, and which, as the result of the experience of the race and of the individual, we have come to consider disagreeable.

Although the various sensations which we experience seem unlike one another, all of them— seeing, hearing, tasting, smelling, and feeling— are produced by similar nerve impulses. When we smell a buttercup or look at it the same kinds of pulses of electric current arc transmitted by nerve fibers to our brain. Which sensation will result depends only on which switchboards in the brain receive the signals. Scrambling of signals is prevented by the fact that each sensory pickup or group of pickups in the eye or nose is connected to a nerve fiber that leads to a specific set of switching centers in the brain. Passed along the fiber from cell to cell, the pulses of current finally reach a group of cells in the brain to which the fiber is attached, and there ring the bell of awareness.

As animals have developed improved sensing mechanisms over the ages, their awareness has gradually grown greater, and they have been able to come increasingly alive. The reliance of more complex creatures in a series on any one sense has not always increased, to be sure. Sensitivity to odors is greatest in certain insects, such as moths, whose smelling cells, located on their antennae, enable them to locate a mate who may be several miles away. Dogs have a much more complex sniffing apparatus than humans, and a large portion of their brain switchboards is devoted to odor. Men now rely on smell much less than in the past, though it still remains closely tied in with their emotions. By far the greatest part of the information we receive from the outside world comes through the sense of sight, yet sight in humans is only about one-eighth as acute as it is in such birds as the hawk. It is the sum total of the signals from the environment, and their integration, that increases as one proceeds toward the complex nerve development of man. In his brain the switchboards became so complex that an entirely new phenomenon, that of reason, was able to appear.

The sense of smell, in some of the higher animals sending messages that required ever more complex switchboards for their full utilization, ultimately resulted in the development of new control rooms, the cerebral hemispheres. In fact, the switching patterns of some of the nerve circuits eventually became so involved as to render them capable of internal stimulation, so that signals could be set going among them even in the absence of sensations from the external world. Man developed the ability to produce, within his brain circuits, reactions almost as effective as those caused by a sound or a smell or a view or any other signal from the outside world. Thus he was enabled to supplement sensation with thought, and could profit from a wide new variety of experiences, most of which he need not actually undergo. He then found himself able to perform all sorts of interesting mental experiments. He was able not only to learn, from experiences that might have occurred but did not, what courses of action to avoid, but he could visualize the experiences of others and benefit by them. He could repeat experiences over and over for assimilation into wisdom. Man thus greatly increased his chance of individual survival, for he could avoid many mistakes that previously would have been fatal. Now he was able to short-circuit much of nature’s old method of trial and error, and attack his problems through the use of reason and judgment.

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THE brain thus became an assemblage of switchboards that correlates sensory signals and determines what integrated action the organism should take as a result. In a human being, it contains a hundred times as many nerve lines as the world’s entire telephone system. It is provided with automatic dialing throughout, and within limits it is self-repairing.

A typical nerve cell from the brain of a man looks, under the microscope, rather like a piece of the root end of a kelp plant. At one end it is covered with what appear to be numerous branching rootlets, while the other end has a long flexible axon or stem. This acts as a connecting wire with tips that can make electrochemical connections with rootlets on any of a number of neighboring cells. Such connections, the synapses, are thus living electrical switches. In some cases a cell can contact any of a thousand neighboring neurons like itself, and thousands can contact it. Thus the axon behaves like the plug-in jack of a telephone switchboard, while the rootlets are the connectors to which the jack can be fitted. In the parts of the brain concerned with instinct the synaptic switches are so constructed as always to follow definite, though involved, patterns of closing and opening; in regions concerned with ideas the connection patterns are more flexible, and can be modified by learning.

The neurons and their connections in the brain of a man are like those in the brain of any other animal, but there are many more of them. The brain of an ant contains only about 250 cells, that of a bee nearly 900. In contrast, the human brain contains some l3 billion cells, about five times as many pink or gray neurons as there are people in the world. As one might expect from their comparative intelligence, a sheep’s brain weighs only one-tenth as much as a man’s, but weight is not the final criterion. The brain of a whale weighs twice as much as that of a man, and that of an elephant three or four times as much, but neither contains the necessary complexity of cells and circuits to give its owner a man’s intelligence.

Such creatures as ants and bees cannot profit much by education, for the few possible connection patterns of their brain cells are well established when they are born, and they behave automatically in response to stimuli from the outside. A worker bee during its month of life is pretty much an automaton, operated by a complex system of servomechanisms built into the structures of its cells when they are first arranged from molecules. The experience of its ancestral line is recorded in its gene structures, molecular memories that over countless generations have changed slowly through mutations and natural selection. Man also has such automatic and instinctive behavior patterns, but he has still others that can be modified by his experience. These potential circuits are given him as a sort of blank check when he is born, with which he can draw on amounts of intelligence that depend on his own efforts.

The more flexible electrochemical processes we call thought take place in the new brain, a vast set of switchboards located in the cortex of the cerebrum. Any creature whose cerebral cortex has been removed can no longer profit by experience, for no longer does it have neurons capable of being connected in new flexible patterns. Birds so treated can still fly, cats can spit and glower, but neither can remember or learn, and without a cerebral cortex there appears to be no true awareness.

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ALTHOUGH nature has been developing the brain for 500 million years, the cerebral cortex began to be elaborated some 100 million years ago. And only within the most recent hundredth of this, a mere million years, has the cerebrum developed sufficiently complex circuits for its possessors to be called men. W hen this stage of development was reached the individual began to emerge as important. W hen an ant is killed he can be replaced by another exactly similar ant, but this is never true of a human being. Worker ants of a given variety are alike even to their brain patterns; because the patterns in a man are flexible, each man is different, and what he becomes depends greatly on what is done with his cerebral cortex, through experience and education, during the formation stages of its action patterns.

Though a person cannot make his brain grow in size or potentiality, over the million years of man’s existence the average size of the human skull has increased in at least two jumps. The oldest skulls yet found that can be called human have room for only about 20 ounces of brain; at a later period this increased to a little over two pounds. Today most men have about three pounds of mental switchboards. More important than size in its effect on human intelligence is the wrinkling of the cerebral cortex, which gives increased area for the connection patterns of flexible thought. Between early man and intermediate man this area doubled, and it has doubled again in modern man. We are well fixed now as to mental circuits, for the brain of each of us contains many more cells than we use effectively, and our intelligence depends less on how many switchboards we have than on how many we choose to relegate to the attic unused.

Anyone who has watched one of the great modern electronic digital computers in operation, with its thousands of tiny pink lights flickering on and off, can readily visualize “brain waves” sweeping across t he billions of cells of our mental switchboards as the synapses open and close, switching pulses of current here and there. New patterns are seen here emerging in nature, for a thought is an electrical pattern, just as is an atom. A nerve may be likened to a proton of thought; the circuit patterns in which the cells are connected are analogous to atoms; and the multiple switchboards of the brain are then like molecular aggregates. All the glorious welter of color, sound, and emotional involvement of our world results from countless tiny pulses of electricity, and all instinct and awareness appear to be the result of their combinations.

Such a picture leads some to feel that the scientist is overmechanizing his concept of thought. From the human standpoint, a beautiful sunset or lovely music is much more real than the electrical impulses, the flows of electrons from atom to atom and cell to cell, that bring them to consciousness. However, all of our ideas are to some extent illusions, and we approach reality only by integrating views of phenomena, made from different angles of approach, in ways that do not lead to contradiction. A scientist has no more right to say that his analysis of a sensation on a particular sublevel of matter is the really correct one than has a poet or mystic who focuses on one emotion or revelation the right to say that he has found the only Truth. Yet each with his own brush can add to the clarity of the picture.

It would be as confusing to describe a “mind” in terms of the millions of switchboards for nerve currents the brain contains as to describe a piano in terms of the particles of wood, felt, and steel of which it is composed. Therefore, it is convenient, though somewhat artificial, to think of our minds as having three parts, related very roughly to different assemblies of switchboards in the brain. In a greatly oversimplified picture these three sections can be thought of respectively as the primary seats of reason, of desire, and of conscience—Freud’s ego, id, and superego, respectively.

The ego or conscious mind, which each of us thinks of incorrectly as his real self, is where thought, reason, and visualization take place. It forms the front assembly room of the imagination. Urged by the id in all sorts of directions that seem immediately desirable, and restrained by the cautioning guidance of the superego, it guides the personality during the hours we are awake.

The surest thing that each of us knows, when he is conscious, is that he is aware of being so. Descartes’s most famous dictum was: “I think, therefore I am.” All animals that possess cerebral hemispheres apparently feel this “I-ness,” or consciousness of self, though it probably increases in sharpness of focus as t he higher brain is elaborated.

Many psychologists think of the “stream of consciousness” as being similar to pictures seen on a moving-picture screen, producing sensations which so overlap that they give the impression of being continuous. For this reason some say that it is illusory to talk about the “mind.” But in an exactly analogous sense matter is an illusion also, for it consists mostly of empty space, and the apparent hardness and solidity of a block of steel or granite arise merely because we feel and observe them with fingers and eyes composed of the same “illusory” matter. In this sense everything is illusory. What the psychologists want is for us to avoid making unjustified assumptions by the careless use of terms such as “mind,” lest we fall into difficulties like those the physicists had with their Another, which they ultimately were forced to abandon.

Most important for us is the fact that consciousness hooks up the past to the present and lets us peer a bit into the future. We feel that we are conscious when awake, and unconscious when asleep, but actually there are many intermediate degrees of consciousness or awareness. The ant, the bee, the crab, and the octopus all have awareness in increasing degrees, but are probably not conscious in the “I” sense at all. A cat is much less conscious than a man, though it may be even more aware of many kinds of things that go on about it.

The sets of switchboards in the human brain that are more highly developed than those of any other animal are those concerned with the production of pictures in the mind, with remembering, with the use of the symbols needed for calculating, understanding, and communicating, and with finding the answers to problems. Such a conscious mind finds itself able to reason, so that it can proceed directly from causes to effects, and correlate human experience over space and time. Int elligence dawns as reason begins to be joined by common sense, prudence, and expediency, and eventually by imagination, the ability to bring separate images together into new associations. With the dawn of creative imagination in man, nature took another great stride forward in her ability to solve problems, a step fully as important as that which she had taken when reason first dawned.

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No PICTURE of crealion is more inspiring than that of a beneficent Creator giving his creatures, not a completed Universe in which to dwell statically, but a universe of ordered and progressive opportunity. Call the gropings of each living creature toward greater awareness blind or directed as you will, the result is the same: continually greater new t hings under the sun.

We can see from the record of evolution that coming alive was a slow process and had to be learned in steps. In fact, it was so slow that the changing of the eye of a newt into a better eye through mutations can be likened to trying experimentally to improve the point of a fountain pen by dropping a million of them at random on the floor. Most such impacts will ruin the pens that suffer them, but once in a while the point of one will be improved. Any way of selectively preserving those pens that improve will give a slow but progressive advance.

When a brain was developed which could reason, and thus complete a realistic cycle of awareness within itself, a new and much more rapid method of experimentation became possible. By reason man is able to rule out, without bothering to perform them, many experiments inevitably doomed to failure. Though natural selection will still operate, he need not depend on the random trial of new patterns for the development of the increased awareness that brings him improved ability to control his life.

An ant cannot purposefully try anything new, and any ant that accidentally did so would be murdered by his colleagues. It is the ant colony as a whole that slowly learns over the ages. In contrast, even an earthworm has enough flexibility of brain to enable it to be taught to turn toward the left or right for food. Though rats are not able to reason to any considerable degree, they can solve such problems as separating round objects from triangular ones when these have to do with health or appetite. Cats, with better brains, can be taught somewhat more, and young dogs a great deal. The higher apes can even learn by insight as well as by trial and error.

As is well known, learning ability diminishes rapidly in dogs more than two years old. Chimpanzees can be educated up to the age of about twelve years, beyond which their brain switching patterns become less flexible. Most human beings can be educated during their first forty years, and many learn well up to eighty. Nowadays many people spend more than a third of their normal lives in being formally educated, and this fraction can be expected to increase to a half or more as science brings more leisure and as we learn how not to deaden the natural curiosity with which everyone is born.

Education can be used to develop improved responses very rapidly in any normal human being. Natives on the Pacific island of Manus were visited by the anthropologist Margaret Mead in 1928, and again twenty-five years later. During her first visit they were ignorant savages living in the equivalent, of the Stone Age. In the intervening generation, as a result of their contact with American soldiers during World War II, they learned many new social customs, became more law-abiding, and developed less greedy and quarrelsome habits. Almost any savage tribe can be civilized rapidly in this way.

It turns out that the level of average intelligence varies little from one race of mankind to another. One of the highest intelligence quotients ever measured was that of a little colored girl who had no white blood whatever. The lack in the suppressed races is not of brain capacity, but of opportunity to cultivate effective use of the brain. In the United States, even climate appears to have a much greater effect on measured intelligence than does race.

Probably there has been little change up or down in man’s average intelligence as measured by reasoning ability during the past five thousand years. A few millennia give too short a time for mutation and selection to produce much improvement in the basic intelligence level. But social forms of development are now relatively much more important to the brain than mutations. The associations of its circuits improve as the id comes under better control, the superego becomes more powerful, and desire, reason, and conscience become better integrated through experience.

Our brains can be much more effectively used as we come to comprehend better the limitations of our ways of t bought. Our ideas tend to gat her into stable closed rings; when one of these snaps shut we feel that we have the truth at last, and are well-satisfied, self-righteous, and willing to defend our views against all comers. We have a closed mind insofar as such self-stabilized ideas are concerned. One of the objectives of education should be to jostle these mental patterns so that rings of small radius can be broken open and combined into larger rings that cover a wider range of associations. As the closed rings of mental complacency open and recombine into wider patterns we become more intelligent, aware, and alive, and are able to react more properly to our env ironment. Such mental patterns can be kept flexible by lubricating them with those emotions which result in interest, and only when interest is present can t hey be enlarged to the fullest extent. But interest or motivation, I he watchword of progressive education, is not enough.

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THE circuits of the mind improve vastly with use and exercise. Thinking in a given way brings an increased blood supply and more nourishment to the cells and synapses involved. The process we call learning consists of setting up mental switching patterns over and over again, to train certain circuits and groups of switchboards to function together. The mind needs to be exercised and disciplined as well as to have its gates thrown open through interest.

Disciplinary studies of the past, such as Latin and Greek, gave all sorts of little mental hooks on which associations could be hung. Science gives equally good associative locations. But so superficial is much of our modern education becoming that the necessary condensation nuclei for thought are not being provided for our citizens of tomorrow.

Much of the educative process in the schools today consists merely of instruction and training, the conveying of facts and the development of skills. Teachers tend less and less to insist that the student learn to focus his attention on trains of thought which etch sharp patterns in t he brain, instead of producing a chaotic opening and closing of mental switches at random, governed by the emot ions of the moment.

Man’s basic curiosity is unbounded. Natural learning is a pleasant process, eagerly sought by every normal youngster. Much of modern education has the effect of suppressing this by setting, in the name of democracy, the same standards of achievement for every child regardless of his capabilities. Educators should look further into the differences between motivated and non-motivated education. Both are needed.

The development of the brain that brought a mind to man resulted not only in one improved method of making evolutionary progress, but in two. The method of natural selection among the products of random mutation often requires millions of experiments to reach one successful result. The methods of reason may require only a hundred. When man developed the ability to jump forward mentally to a correct conclusion by the new associative process we call creative imagination, it could often be reached on the first or second attempt, as when Newton arrived by inference at the Law of Universal Gravitation. Most human progress now results from just such creative imagination, based on a properly balanced mixture of intelligence and emotion.

The factor in which a true genius excels is often not judgment or memory or even intelligence, but creative imagination, the highest achievement of man’s new brain. The remarkable human capacity to see, in what we call the mind’s eye, images of things that our eyes have never seen makes it possible, in addition to bringing together new mental patterns of things unseen, to bring from the unconscious mind striking new combinations of thought patterns. This we call inspiration. In the unconscious mind, cell-connection patterns boil ceaselessly around in all sorts of random arrangements. Most of these are meaningless or useless, and the images they would produce are faulty, but a strikingly meaningful set of images occasionally becomes associated in the brain of a person having a fertile imagination, and can rise rapidly into the conscious mind.

Poets frequently emphasize that they do not know what a poem they are writing is about until they have finished it. This has been taken by some to indicate that inspiration comes from unknown worlds behind the mind, but it appears rather to come from inner parts of the mind, and hence to be a product of the brain itself. Much of a newly created concept is put together in the unconscious, and it then is dredged out, either in pieces or as a whole, into the conscious, where it can be polished.

As time goes on, the use of creative imagination is likely to become more a normal human experience than that of the unusual genius. The brain may, once in five or fifty thousand years, mutate in new directions of complexity. It will certainly long before that be supplemented by additional external informational devices of the type man has been fashioning ever since he learned to chisel his first memoirs in stone. In any case, as new demands are made on the brain by the increasing complexities of living, it is likely to respond by developing new associative processes lying as far beyond reason and imagination as these are beyond the mental processes of the beasts that inhabit the fields.