Asimov's New Guide to Science

by Isaac Asimov

The trouble is that no test has been devised that is not culturally centered. Simple questions about ploughs might stump an intelligent city boy, and simple questions about escalators might stump an equally intelligent farm boy. Both would puzzle an equally intelligent Australian aborigine, who might nevertheless dispose of questions about boomerangs that would leave us gasping.

  What is more, it is difficult for people not to have preconceived notions about who is intelligent and who is not. An investigator is bound to find higher intelligence in culturally similar subjects. Stephen Jay Gould in his book The Mismeasure of Man (1981) describes in full detail how I.Q. measurements ever since the First World War have been placed at the service of unconscious or taken-for-granted racism.

  The most recent and blatant example is that of the British psychologist Cyril Lodowic Burt, who was educated at Oxford and taught both at Oxford and Cambridge. He studied the I.Q.‘s of children and correlated those I.Q.‘s with the occupational status of the parents: higher professional, lower professional, clerical, skilled labor, semiskilled labor, unskilled labor.

  He found that the I.Q.‘s fit those occupations perfectly. The lower the parent was in the social scale, the lower the I.Q. of the child. In other words, people belonged where they were, and those who were better off deserved to be.

  Furthermore, Burt found that men had higher I.Q.‘s than women, Englishmen than Irishmen, Gentiles than Jews, and so on. He tested identical twins who were separated soon after birth and found that their I.Q.‘s were nevertheless very similar—again pointing out the great importance of heredity over environment.

  Burt was greatly honored and was knighted before his death in 1971. After his death, however, it was discovered that, quite beyond doubt, he had fabricated his data.

  It is not necessary to go into the psychological reasons for this. It is sufficient (to me) that people are so anxious to be considered intelligent that it is next to impossible for them to find figures that would yield opposite results. The whole field of intelligence testing is so involved with emotion and self-love that any results must be approached very cautiously.

  Another familiar test is aimed at an aspect of the mind even more subtle and elusive than intelligence. This consists of ink-blot patterns first prepared by a Swiss doctor, Hermann Rorschach, between 1911 and 1921. Subjects are asked to convert these ink blots into images; from the type of image a person builds into such a Rorschach test; conclusions concerning his or her personality are drawn. Even at best, however, such conclusions are not likely to be truly conclusive.

  THE SPECIALIZATION OF FUNCTIONS

  Oddly enough, many of the ancient philosophers almost completely missed the significance of the organ under the human skull. Aristotle considered the brain merely an air-conditioning device, so to speak, designed to cool the overheated blood. In the generation after Aristotle, Herophilus of Chacedon, working at Alexandria, correctly recognized the brain as the seat of intelligence, but, as usual, Aristotle’s errors carried more weight than did the correctness of others.

  The ancient and medieval thinkers therefore often tended to place the seat of emotions and personality in organs such as the heart, the liver, and the spleen (vide the expressions “broken-hearted,” “lily-livered,” “vents his spleen”).

  The first modern investigator of the brain was a seventeenth-century English physician and anatomist named Thomas Willis; he traced the nerves that led to the brain. Later, a French anatomist named Felix Vicq d’Azyr and others roughed out the anatomy of the brain itself. But it was the eighteenth-century Swiss physiologist Albrecht von Haller who made the first crucial discovery about the functioning of the nervous system.

  Von Haller found that he could make a muscle contract much more easily by stimulating a nerve than by stimulating the muscle itself. Furthermore, this contraction was involuntary; he could even produce it by stimulating a nerve after the organism had died. Van Haller went on to show that the nerves carry sensations. When he cut the nerves attached to specific tissues, these tissues could no longer react. The physiologist concluded that the brain receives sensations by way of nerves and then sends out, again by way of nerves, messages that lead to such responses as muscle contraction. He supposed that the nerves all come to a junction at the center of the brain.

  In 1811 the Austrian physician Franz Joseph Gall focused attention on the gray matter on the surface of the cerebrum (which is distinguished from the white matter in that the latter consists merely of the fibers emerging from the nerve-cell bodies, these fibers being white because of their fatty sheaths). Gall suggested that the nerves do not collect at the center of the brain as von Haller had thought, but that each runs to some definite portion of the gray matter, which he considered the coordinating region of the brain. Gall reasoned that different parts of the cerebral cortex are in charge of collecting sensations from different parts of the body and sending out the messages for responses to specific parts as well.

  If a specific part of the cortex is responsible for a specific property of the mind, what is more natural than to suppose that the degree of development of that part would reflect a person’s character or mentality? By feeling for bumps on a person’s skull, one might find out whether this or that portion of the brain was enlarged and so judge whether a person was particularly generous or particularly depraved or particularly something else. With this reasoning, some of Gall’s followers founded the pseudo-science of phrenology, which had quite a vogue in the nineteenth century and is not exactly dead even today. (Oddly enough, although Gall and his followers emphasized the high forehead and domed head as a sign of intelligence—a view that still influences people today—Gall himself had an unusually small brain, about 15 percent smaller than the average.)

  But the fact that phrenology, as developed by charlatans, is nonsense, does not mean that Gall’s original notion of the specialization of functions in particular parts of the cerebral cortex was wrong. Even before specific explorations of the brain were attempted, it was noted that damage to a particular portion of the brain might result in a particular disability. In 1861, the French surgeon Pierre Paul Broca, by assiduous postmortem study of the brain, was able to show that patients with aphasia (the inability to speak, or to understand speech) usually possessed physical damage to a particular area of the left cerebrum, an area called Broca’s convolution as a result.

  Then, in 1870, two German scientists, Gustav Fritsch and Eduard Hitzig, began to map the supervisory functions of the brain by stimulating various parts of it and observing what muscles responded. A half-century later, this technique was greatly refined by the Swiss physiologist Walter Rudolf Hess, who was awarded a share of the 1949 Nobel Prize for medicine and physiology in consequence.

  It was discovered by such methods that a specific band of the cortex was particularly involved in the stimulation of the various voluntary muscles into movement. This band is therefore called the motor area. It seems to bear a generally inverted relationship to the body; the uppermost portions of the motor area, toward the top of the cerebrum, stimulate the lowermost portions of the leg; as one progresses downward in the motor area, the muscles higher in the leg are stimulated, then the muscles of the torso, then those of the arm and hand, and finally those of the neck and hand.

  Behind the motor area is another section of the cortex that receives many types of sensation and is therefore called the sensory area. As in the case of the motor area, the regions of the sensory area in the cerebral cortex are divided into sections that seem to bear an inverse relation to the body. Sensations from the foot are at the top of the area, followed successively as we go downward with sensations from leg, hip, trunk, neck, arm, hand, fingers, and, lowest of all, the tongue. The sections of the sensory area devoted to lips, tongue, and hand are (as one might expect) larger in proportion to the actual size of those organs than are the sections devoted to other parts of the body.

  If, to the motor area and the sensory area, are added those sections of the cerebral cort
ex primarily devoted to receiving the impressions from the major sense organs, the eye and the ear, there still remains a major portion of the cortex without any clearly assigned and obvious function.

  It is this apparent lack of assignment that has given rise to the statement, often encountered, that the human being “uses only one-fifth of his brain.” That, of course, is not so; the best we can really say is that one-fifth of the human brain has an obvious function. We might as well suppose that a construction firm engaged in building a skyscraper is using only one-fifth of its employees because that one-fifth is actually engaged in raising steel beams, laying down electric cables, transporting equipment, and such. This assumption would ignore the executives, secretaries, filing clerks, supervisors, and others. Analogously, the major portion of the brain is engaged in what we might call white-collar work, in the assembling of sensory data, in its analysis, in deciding what to ignore, what to act upon, and just how to act upon it. The cerebral cortex has distinct association areas—some for sound sensations, some for visual sensations, some for others.

  When all these association areas are taken into account, there still remains one area of the cerebrum that has no specific and easily definable function. This is the area just behind the forehead, which is called the prefrontal lobe. Its lack of obvious function is such that it is sometimes called the silent area. Tumors have made it necessary to remove large areas of the prefrontal lobe without any particular significant effect on the individual; yet surely it is not a useless mass of nerve tissue.

  One might even suppose it to be the most important portion of the brain if one considers that, in the development of the human nervous system, there has been a continual piling up of complication at the forward end. The prefrontal lobe might therefore be the brain area most recently evolved and most significantly human.

  In the 1930s, it seemed to a Portuguese surgeon, Antonio Egas Moniz, that where a mentally ill patient was at the end of his rope, it might be possible f to help by taking the drastic step of severing the prefrontal lobes from the rest of the brain. The patient might then be cut off from a portion of the associations he had built up, which were, apparently, affecting him adversely, and make a fresh and better start with the brain he had left. This operation, prefrontal lobotomy, was first carried out in 1935; in a number of cases, it did indeed seem to help. Moniz shared (with W. R. Hess) the Nobel Prize for medicine and physiology in 1949 for his work. Nevertheless, the operation never achieved popularity and is less popular now than ever. Too often, the cure is literally worse than the disease.

  The cerebrum is actually divided into two cerebral hemispheres connected by a tough bridge of white matter, the corpus callosum. In effect, the hemispheres are separate organs, unified in action by the nerve fibers that cross the corpus callosum and act to coordinate the two. Nonetheless, the hemispheres remain potentially independent.

  The situation is somewhat analogous to that of our eyes. Our two eyes act as a unit ordinarily, but if one eye is lost, the other can meet our needs. Similarly, the removal of one of the cerebral hemispheres does not make an experimental animal brainless; the remaining hemisphere learns to carry on.

  Ordinarily, each hemisphere is largely responsible for a particular side of the body; the left cerebral hemisphere for the right side, the right cerebral hemisphere for the left side. If both hemispheres are left in place and the corpus callosum is cut, coordination is lost, and the two body halves come under more or less independent control. A literal case of twin brains, so to speak, is set up.

  Monkeys can be so treated (with further operation upon the optic nerve to make sure that each eye is connected to only one hemisphere), and when this is done, each eye can be separately trained to do particular tasks. A monkey can be trained to select a cross over a circle to indicate, let us say, the presence of food. If only the left eye is kept uncovered during the training period, only the left eye will be useful in this respect. If the right eye is uncovered and the left eye covered, the monkey will have no right-eye memory of its training. It will have to hunt for its food by trial and error. If the two eyes are trained to contradictory tasks and if both are then uncovered, the monkey alternates activities, as the hemispheres politely take their turns.

  Naturally, in any such “two in charge” situation, there is always the danger of conflict and confusion. To avoid that, one cerebral hemisphere (almost always the left one in human beings) is dominant, when both are normally connected. Broca’s convolution, which controls speech, is in the left hemisphere, for instance. The gnostic area, which is an over-all association area, a kind of court of highest appeal, is also in the left hemisphere. Since the left cerebral hemisphere controls the motor activity of the right-hand side of the body, it is not surprising that most people are right-handed (though even left-handed people usually have a dominant left cerebral hemisphere). Where clear-cut dominance is not established between left and right, there may be ambidexterity, rather than a clear right-handedness or left-handedness, along with some speech difficulties and, perhaps, manual clumsiness.

  It has become fashionable in recent years to suppose that the two halves of the brain think differently. The left hemisphere, which is clearly in control of speech, would think logically, mathematically, step by step. The right hemisphere would be left with intuition, artistic conception, thinking as a whole.

  The cerebrum is not the whole of the brain. There are areas of gray matter embedded below the cerebral cortex. These are called the basal ganglia; included is a section called the thalamus (see figure 17.2). The thalamus acts as a reception center for various sensations. The more violent of these—such as pain, extreme heat or cold, or rough touch—are filtered out. The milder sensations from the muscles—the gentle touches, the moderate temperatures—are passed on to the sensory area of the cerebral cortex. It is as though mild sensations can be trusted to the cortex, where they can be considered judiciously and where reaction can come after a more or less prolonged interval of consideration. The rough sensations, however, which must be dealt with quickly and for which there is no time for consideration, are handled more or less automatically in the thalamus.

  Underneath the thalamus is the hypothalamus, center for a variety of devices for controlling the body. The body’s appestat, mentioned in chapter 15 as controlling the body’s appetite, is located there; so is the control of the body’s temperature. It is through the hypothalamus, moreover, that the brain exerts at least some influence over the pituitary gland (see chapter 15); this is an indication of the manner in which the nervous controls of the body and the chemical controls (the hormones) can be unified into a master supervisory force.

  In 1954, the physiologist James Olds discovered another and rather frightening function of the hypothalamus. It contains a region that, when stimulated, apparently gives rise to a strongly pleasurable sensation. An electrode affixed to the pleasure center of a rat, so arranged that it can be stimulated by the animal itself, will be stimulated up to 8,000 times an hour for hours or days at a time, to the exclusion of food, sex, and sleep. Evidently, all the desirable things in life are desirable only insofar as they stimulate the pleasure center. To stimulate it directly makes all else unnecessary.

  The hypothalamus also contains an area that has to do with the wake-sleep cycle, since damage to parts of it induces a sleeplike state in animals. The exact mechanism by which the hypothalamus performs its function is uncertain. One theory is that it sends signals to the cortex, which sends signals back in response, in mutually stimulating fashion. With continuing wakefulness, the coordination of the two fails, the oscillations become ragged, and the individual becomes sleepy. A violent stimulus (a loud noise, a persistent shake of the shoulder, or, for that matter, a sudden interruption of a steady noise) will arouse one. In the absence of such stimuli, coordination will be restored eventually between hypothalamus and cortex, and sleep will end spontaneously; or perhaps sleep will become so shallow that a perfectly ordinary stimulus, of which the su
rroundings are always full, will suffice to wake one.

  During sleep, dreams—sensory data more or less divorced from reality—will take place. Dreaming is apparently a universal phenomenon; people who report dreamless sleep are merely failing to remember their dreams. The American physiologist William Dement, studying sleeping subjects in 1952, noticed periods of rapid eye movements that sometimes persisted for minutes (REM sleep). During this period, one’s breathing, heartbeat, and blood pressure, rose to waking levels. This takes place about a quarter of the sleeping time. A sleeper who was awakened during these periods generally reported having had a dream. Furthermore, a sleeper who was continually disturbed during these periods began to suffer psychological distress; the periods of distress were multiplied during succeeding nights as though to make up for the lost dreaming.

  It would seem, then, that dreaming has an important function in the working of the brain. It is suggested that dreaming is a device whereby the brain runs over the events of the day to remove the trivial and repetitious that might otherwise clutter it and reduce its efficiency. Sleep is the natural time for such activity, for the brain is then relieved of many of its waking functions. Failure to accomplish this task (because of interruption) may so clog the brain that clearing attempts must be made during waking periods, producing hallucinations (that is, waking dreams, so to speak) and other unpleasant symptoms. One might naturally wonder if this is not a chief function of sleep: since there is very little physical resting in sleep that cannot be duplicated by quiet wakefulness. REM sleep even occurs in infants who spend half their sleeping time at it and who would seem to lack anything about which to dream. It may be that REM sleep helps the development of the nervous system. (It has been observed in mammals other than humans, too.)

  THE SPINAL CORD

  Below the cerebrum is the smaller cerebellum (also divided into two cerebellar hemispheres) and the brain stem, which narrows and leads smoothly into the spinal cord extending about 18 inches down the hollow center of the spinal column.