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Asimov's New Guide to Science

Page 115

by Isaac Asimov


  In the normal course, the nerve endings of the sympathetic nervous system themselves secrete a compound very like adrenalin, called noradrenalin. This chemical serves to carry the nerve impulses across the synapses, transmitting the message by stimulating the nerve endings on the other side of the gap.

  In the early 1920s the English physiologist Henry Dale and the German physiologist Otto Loewi (who were to share the Nobel Prize in physiology and medicine in 1930) studied a chemical that performed this function for most of the nerves other than those of the sympathetic system. The chemical is called acetylcholine. It is now believed to be involved not only at the synapses but also in conducting the nerve impulse along the nerve fiber itself. Perhaps acetylcholine acts upon the sodium pump. At any rate, the substance seems to be formed momentarily in the nerve fiber and to be broken down quickly by an enzyme called cholinesterase. Anything that inhibits the action of cholinesterase will interfere with this chemical cycle and will stop the transmission of nerve impulses. The deadly substances now known as nerve gases are cholinesterase inhibitors. By blocking the conduction of nerve impulses, they can stop the heartbeat and produce death within minutes. The application to warfare is obvious. They can be used, less immorally, as insecticides.

  A less drastic interference with cholinesterase is that of local anesthetics, which in this way suspend (temporarily) those nerve impulses associated with pain.

  Thanks to the electric currents involved in nerve impulses, it is possible to “read” the brain’s activity, in a way, though no one has yet been able to translate fully what the brain waves are saying. In 1929, a German psychiatrist, Hans Berger, reported earlier work in which he applied electrodes to various parts of the head and was able to detect rhythmic waves of electrical activity.

  Berger gave the most pronounced rhythm the name of alpha wave. In the alpha wave, the potential varies by about 20 microvolts in a frequency of roughly 10 times a second. The alpha wave is clearest and most obvious when the subject is resting with eyes closed. When the eyes are open but viewing featureless illumination, the alpha wave persists. If, however, the ordinary variegated environment is in view, the alpha view vanishes, or is drowned, by other more prominent rhythms. After a while, if nothing visually new is presented, the alpha wave reappears. Typical names for other types of waves are beta waves, delta waves, and theta waves.

  Electroencephalograms (“electrical writings of the brain” or, as abbreviated, EEG) have since been extensively studied and show that each individual has his or her own pattern, varying with excitement and in sleep. Although the electroencephalogram is still far from being a method of “reading thoughts” or tracing the mechanism of the intellect, it does help in the diagnosis of major upsets of brain function, particularly epilepsy. It can also help locate areas of brain damage or brain tumors.

  In the 1960s, specially designed computers were called into battle. If a particular small environmental change is applied to a subject, it is presumed that there will be some response in the brain that will be reflected in a small alteration in the EEG pattern at the moment when the change is introduced. The brain will be engaged in many other activities, however, and the small alteration in the EEG will not be noticeable. Notwithstanding, if the process is repeated over and over again, a computer can be programed to average out the EEG pattern and find the consistent difference.

  By 1964, the American psychologist Manfred Clynes reported analyses fine enough to be able to tell, by a study of the EEG pattern alone, what color a subject was looking at. The English neurophysiologist William Grey Walter similarly reported a brain-signal pattern that seems characteristic of the learning process. It comes when the subject under study has reason to think he or she is about to be presented with a stimulus that will call for thought or action. Walter calls it the expectancy wave and points out that it is absent in children under three and in certain psychotics. The reverse phenomenon, that of bringing about specific actions through direct electrical stimulation of the brain, was also reported in 1965. Jose Manuel Rodriguez Delgado of Yale, transmitting electrical stimulation by radio signals, caused animals to walk, climb, yawn, sleep, mate, switch emotions, and so on at command. Most spectacularly, a charging bull was made to stop short and trot peacefully away.

  Human Behavior

  Unlike physical phenomena, such as the motions of planets or the properties of light, the behavior of living things has never been reduced to rigorous natural laws and perhaps never will be. There are many who insist that the study of human behavior cannot become a true science, in the sense of being able to explain or predict behavior in any given situation on the basis of universal natural laws. Yet life is no exception to the rule of natural law, and it can be argued that living behavior would be fully explainable if all the factors were known. The catch lies in that last phrase. It is unlikely that all the factors will ever be known; they are too many and too complex. We need not, however, despair of ever being able to improve our understanding of ourselves. There is ample room for better knowledge of our own mental complexities, and even if we never reach the end of the road, we may yet hope to travel along it quite a way.

  Not only is the subject particularly complex, but its study has not been progressing for long. Physics came of age in 1600, and chemistry in 1775, but the much more complex study of experimental psychology dates only from 1879, when the German physiologist Wilhelm Wundt set up the first laboratory devoted to the scientific study of human behavior. Wundt interested himself primarily in sensation and in the manner in which humans perceive the details of the universe about them.

  At almost the same time, the study of human behavior in one particular application—that involving the individual as an industrial cog—arose. In 1881, the American engineer Frederick Winslow Taylor began measuring the time required to do certain jobs and to work out methods for so organizing the work as to minimize that time. He was the first efficiency expert and was (like all efficiency experts who tend to lose sight of values beyond the stop watch) unpopular with the workers.

  But as we study human behavior, step by step, either under controlled conditions in a laboratory or empirically in a factory, it does seem that we are tackling a fine machine with blunt tools.

  In the simple organisms we can see direct, automatic responses of the kind called tropisms (from a Greek word meaning “to turn”). Plants show phototropism (“turning toward light”), hydrotropism (“turning toward water,” in this case by the roots), and chemotropism (“turning toward particular chemical substances”). Chemotropism is also characteristic of many animals, from protozoa to ants. Certain moths are known to fly toward a scent as far as 2 miles away. That tropisms are completely automatic is shown by the fact that a phototropic moth will even fly into a candle flame.

  The reflexes mentioned earlier in this chapter do not seem to progress far beyond tropisms, and imprinting, also mentioned, represents learning, but in so mechanical a fashion as scarcely to deserve the name. Yet neither reflexes nor imprinting can be regarded as characteristic of the lower animals only; human beings have their share.

  CONDITIONED RESPONSES

  The human infant from the moment of birth will grasp a finger tightly if it touches his palm and will suck at a nipple if that is put to his lips. The importance of such instincts to keep the infant secure from falling and from starvation is obvious.

  It seems almost inevitable that the infant is subject also to imprinting. This is not a fit subject for experimentation, of course, but knowledge can be gained through incidental observations. Children who, at the babbling stage, are not exposed to the sounds of actual speech may not develop the ability to speak later, or do so to an abnormally limited extent. Children brought up in impersonal institutions where they are efficiently fed and their physical needs are amply taken care of, but where they are not fondled, cuddled, and dandled, become sad little specimens indeed. Their mental and physical development is greatly retarded and many die for no other reason apparently
than lack of mothering—by which may be meant the lack of adequate stimuli to bring about the imprinting of necessary behavior patterns. Similarly, children who are unduly deprived of the stimuli involved in the company of other children during critical periods in childhood develop personalities that may be seriously distorted in one fashion or another.

  Of course, one can argue that reflexes and imprinting are a matter of concern only for infancy. When one achieves adulthood, one is then a rational being who responds in more than a mechanical fashion. But does one? To put it another way: Do we possess free will (as we like to think)? Or, is our behavior in some respects absolutely determined by the stimulus, as the bull’s was in Delgado’s experiment I have just described?

  One can argue for the existence of free will on philosophical or theological grounds, but I know of no one who has ever found a way to demonstrate it experimentally. To demonstrate determinism, the reverse of free will, is not exactly easy either. Attempts in that direction, however, have been made. Most notable were those of the Russian physiologist Ivan Petrovich Pavlov.

  Pavlov started with a specific interest in the mechanism of digestion. He showed, in the 1880s, that gastric juice was secreted in the stomach as soon as food was placed on a dog’s tongue; the stomach would secrete this juice even if food never reached it. But if the vagus nerve (which runs from the medulla oblongata to various parts of the alimentary canal) was cut near the stomach, the secretions stopped. For his work on the physiology of digestion, Pavlov received the Nobel Prize in physiology and medicine in 1904. But like some other Nobel laureates (notably, Ehrlich and Einstein) Pavlov went on to other discoveries that dwarfed the accomplishments for which he actually received the prize.

  He decided to investigate the automatic, or reflex, nature of secretions, and he chose the secretion of saliva as a convenient, easy-to-observe example. The sight or odor of food causes a dog (and a human being, for that matter) to salivate. What Pavlov did was to ring a bell every time he placed food before a dog. Eventually, after twenty to forty associations of this sort, the dog salivated when it heard the bell even though no food was present. An association had been built up. The nerve impulse that carried the sound of the bell to the cerebrum had become equivalent to one representing the sight or the odor of food.

  In 1903, Pavlov invented the term conditioned reflex for this phenomenon; the salivation was a conditioned response. Willy-nilly, the dog salivated at the sound of the bell just as it would at the sight of food. Of course, the conditioned response could be wiped out—for instance, by repeatedly denying food to the dog when the bell was rung and subjecting it to a mild electric shock instead. Eventually, the dog would not salivate but instead would wince at the sound of the bell, even though it received no electric shock.

  Furthermore, Pavlov was able to force dogs to make subtle decisions by associating food with a circular patch of light and an electric shock with an elliptical patch. The dog could make the distinction, but as the ellipse was made more and more nearly circular, distinction became more difficult. Eventually, the dog, in an agony of indecision, developed what could only be called a nervous breakdown.

  Conditioning experiments have thus become a powerful tool in psychology. Through them, animals sometimes almost talk to the experimenter. The technique has made it possible to investigate the learning abilities of various animals, their instincts, their visual abilities, their ability to distinguish colors, and so on. Of all the investigations, not the least remarkable are those of the Austrian naturalist Karl von Frisch. Von Frisch trained bees to go to dishes placed in certain locations for their food, and he learned that these foragers soon told the other bees in their hive where the food was located. From his experiments von Frisch learned that the bees could distinguish certain colors—including ultraviolet, but excluding red—which they communicated with one another by means of a dance on the honeycombs; that the nature and vigor of the dance told the direction and distance of the food dish from the hive and even how plentiful or scarce the food supply was; and that the bees were able to tell direction from the polarization of light in the sky. Von Frisch’s fascinating discoveries about the language of the bees opened up a whole new field of study of animal behavior.

  In theory, all learning can be considered to consist of conditioned responses. In learning to type, for instance, you start by watching the typewriter keyboard and gradually substitute certain automatic movements of the fingers for visual selection of the proper key. Thus the thought k is accompanied by a specific movement of the middle finger of the right hand; the thought the causes the first finger of the left hand, the first finger of the right hand, and the second finger of the left hand, to hit certain spots in that order. These responses involve no conscious thought. Eventually a practiced typist has to stop and think to recall where the letters are. I am myself a rapid and completely mechanical typist, and if I am asked where the letter f, say, is located on the keyboard, the only way I can answer (short of looking at the keyboard) is to move my fingers in the air as if typing and try to catch one of them in the act of typing f. Only my fingers know the keyboard; my conscious mind does not.

  The same principle may apply to more complex learning, such as reading or playing a violin. Why, after all, does the design CRAYON in black print on this piece of paper automatically evoke a picture (to an English-speaking person) of a pigmented stick of wax and a certain sound that represents a word? You do not need to spell out the letters or search your memory or reason out the possible message contained in the design; from repeated conditioning, you automatically associate the symbol with the thing itself.

  In the early decades of this century, the American psychologist John Broadus Watson built a whole theory of human behavior, called behaviorism, on the basis of conditioning. Watson went so far as to suggest that people have no deliberate control over the way they behave; it is all determined by conditioning. Although his theory was popular for a time, it never gained wide support among psychologists. In the first place, even if the theory is basically correct—if behavior is dictated solely by conditioning—behaviorism is not very enlightening on those aspects of human behavior that are of most interest to us, such as creative intelligence, artistic ability, and the sense of right and wrong. It would be impossible to identify all the conditioning influences and relate them to the pattern of thought and belief in any measurable way; and something that cannot be measured is not subject to any really scientific study.

  In the second place, what does conditioning have to do with a process such as intuition? The mind suddenly puts two previously unrelated thoughts or events together, apparently by sheer chance, and creates an entirely new idea or response.

  Cats and dogs, in solving tasks (as in finding out how to work a lever in order to open a door) may do so by a process of trial and error. They may move about randomly and wildly until some motion of theirs trips the lever. If they are set to repeating the task, a dim memory of the successful movement may lead them to it sooner, and then still sooner at the next attempt, until finally they move to the lever at once. The more intelligent the animal, the fewer attempts will be required to graduate from sheer trial and error to purposive useful action.

  By the time we reach people, memory is no longer feeble. Your tendency might be to search for a dropped dime by glances randomly directed at the floor, but from past experience you may look in places where you have found the dime before, or look in the direction of the sound, or institute a systematic scanning of the floor. Similarly, if you were in a closed place, you might try to escape by beating and kicking at the walls randomly; but you would also know what a door would look like and would concentrate your efforts on that.

  People can, in short, simplify trial and error by calling on years of experience, and transfer it from thought to action. In seeking a solution, you may do nothing, you may merely act in thought. It is this etherealized trial and error we call reason, and it is not even entirely restricted to the human species.
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br />   Apes, whose patterns of behavior are simpler and more mechanical than ours, show some spontaneous insight, which may be called reason. The German psychologist Wolfgang Köhler, trapped in one of the German colonies in Africa by the advent of the First World War, discovered some striking illustrations of this insight in his famous experiments with chimpanzees. In one case a chimp, after trying in vain to reach bananas with a stick that was too short, suddenly picked up another bamboo stick that the experimenter had left lying handy, joined the two sticks together, and so brought the fruit within reach. In another instance, a chimp piled one box on another to reach bananas hanging overhead. These acts had not been preceded by any training or experience that might have formed the association for the animal; apparently they were sheer flashes of inspiration.

  To Köhler, it seemed that learning involved the entire pattern of a process, rather than individual portions of it. He was one of the founders of the Gestalt school of psychology (Gestalt being the German word for “pattern”).

  Chimpanzees and the other great apes are so nearly human in appearance and in some of their behavior that there have not been lacking attempts to bring up young apes with human children in order to see how long they would keep up with the latter. At first, maturing more quickly, young apes forge ahead of their human counterparts. However, once human children learn to speak, the apes fall behind forever. They lack the equivalent of Broca’s convolution.

  In the wild, however, chimpanzees communicate not only by a small catalogue of sounds but by gesture. It occurred to Beatrice and Allen Gardner at the University of Nevada, in 1966, to try to teach a sign language to a one-and-one-half-year-old female chimpanzee named Washoe. They were amazed at the results. Washoe learned dozens of symbols, used them correctly, and understood them easily.

 

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