The Intelligent Man's Guide to Intelligence

As if there weren't enough controversy in our time, people are now fighting about intelligence—not the CIA type but the kind that Webster's Dictionary defines as: "the faculty of understanding; the capacity to know or apprehend." What could be debatable about that? Listen:

• Sir Charles Snow, the eminent British novelist and scientist—and a liberal—says in March 1969 that the astonishing disproportion of Jews among Nobel Prize winners and other outstandingly intelligent groups suggests that "there [is] something in the Jewish gene-pool which produces talent on quite a different scale from, say, the Anglo-Saxon gene-pool." For this, he draws a fierce barrage of criticism from non-Jews and Jews—many of them liberals—who call his suggestion "benign racism" and a "mirror image" of Nazi racist theories.

• The Los Angeles City Council, following the lead of New York City and Washington, D.C., votes in early 1969 to eliminate I.Q. testing from the lower grades of public schools. The cause: pressure by militant Negroes and other disadvantaged people, who regard I.Q. testing as one of Whitey's tricks to keep them out of college and the better schools. They have some odd bedfellows: The John Birch Society has been attacking I.Q. testing for years, on the ground that it is an effort by Big Government to control the minds of Americans.

• Psychologist Arthur Jensen, of the University of California at Berkeley, publishes a long, dense, scholarly paper in the Harvard Educational Review, using statistical methods to show that heredity is far more responsible than environment for differences in tested intelligence and suggesting that this may account for most of the 15-point difference between average white and Negro I.Q. scores. Dozens of newspapers and magazines find this article "inflammatory" and "incendiary." In the staid, academic pages of the Harvard Educational Review, various scholars and educators term his article "mischievous" and "unforgivable" and label him a "high priest of racism." At Berkeley, his office is picketed by the SDS, black students try to disrupt his classes and his safety is threatened via mail and phone.

• In October 1969, physicist William Shockley, of Stanford University, arises to deliver an address to a National Academy of Sciences meeting held at Dartmouth College. Shockley, a Nobel Prize winner as coinventor of the transistor, wants the academy to support research on the inheritance of intelligence. As soon as he is introduced, some 40 Negro students begin clapping loudly—and keep it up for 90 minutes, until Shockley and the administrative staff call the meeting off.

• A militant social-reform group named American Psychologists for Social Action circulates an anti-Jensen, anti-I.Q.-testing petition. One of the more vocal members of the organization, Dr. Martin Deutsch, of New York University, tells me: "There's no scientific definition of intelligence at this time. It's a convenient label for certain kinds of behavior; but I suspect that, in actual fact, the thing itself doesn't really exist."

Intelligence doesn't exist? What's he talking about? Don't we all know it exists? Even when we were children, we could tell which kids around us were smart and which were dumb. As adults, we have a fair idea, after a few minutes of conversation, whether a new acquaintance is bright or stupid and, after spending some time with any person, we know which he is. But our everyday experiences of intelligence do not tell us exactly what it is; they do not even prove its existence.

However, we have more than everyday experiences to go by; indeed, in the past 66 years, no subject in all of psychology has been so extensively researched and put to practical use as has intelligence. Each year, millions of I.Q. tests are given to school children, college students, draftees and job applicants. Articles, monographs and books on new research in intelligence appear at the rate of one a day. Current research concerns a wide variety of topics: the development of many new kinds of tests; the relationship of intelligence scores to social class, to ethnic origins, to the time and place of testing and even to the sex of the tester; the chemistry of the brain; problem-solving ability in pigeons, rats, cats, dogs, WASPs and Negroes; and such arcana as the representation of the structure of intellect by a three-dimensional matrix. Dr. Deutsch must be wrong; some of these people must know something about the subject.

And they do; the trouble is that they disagree about the meaning of most of what they know. Incompatible theories of intelligence exist in embarrassing profusion. The oldest was formulated half a century ago by English psychologist Charles Spearman, who noted that many mental abilities are statistically correlated: A person who does well in vocabulary is likely to do well in arithmetic, pencil-and-paper mazes and so on; a person, who does poorly in one of them is likely to do poorly in the others. To Spearman, this clearly suggested that an unseen general intelligence, or g, lay behind the various specific abilities, or s's, and made all the scores go one way or the other. But what was g itself? Spearman could only suggest that it was the ability to perceive relationships or connections between things.

Most psychologists accepted g as a reality; a number of them, in fact, set about improving upon, and complicating, Spearman's basic theory. Louis Thurstone, of the University of Chicago, an authority on intelligence, and others found "group factors" common to bunches of s's—higher than s's, but still subordinate to g. Raymond Cattell, now with the University of Illinois, and various others found not one but two kinds of g; one provides the brain power for routine learned abilities such as vocabulary, another provides the brain power for less teachable and more complex abilities such as abstract reasoning. Some psychologists eventually decided that g doesn't really explain anything and that the theory might as well be junked. J. P. Guilford and his students at the University of Southern California identified many highly specialized mental abilities—more than 80, at last count—and organized them into a kind of three-dimensional structure, in which all are of equal merit and there is no overriding unseen "pure" intelligence. The brilliant Swiss psychologist Jean Piaget has, meanwhile, ignored practically the entire business of g, s, I.Q. and testing; instead, he has studied intelligence as a living, growing thing and described its functions in the various stages of the mind's development.

Those are some of the theories at the present time. Each answers some questions, raises others, ignores yet others. But not all is chaos. There are two distinct sides in the intelligence war and, on nearly every debated issue, psychologists are in one camp or the other. The two are those old classic opposites, nature versus nurture, heredity versus environment, instinct versus experience—the-very same polarization of views that exists in the field of animal-behavior studies, between the instinct-oriented ethologists and the developmentalists. (See Man and Beast, Playboy, July 1970.)

Hereditarians think that intelligence is essentially based on the individual's brain structure and chemistry, and hence is largely predetermined by his genetic make-up. Environmentalists think intelligence consists primarily of acquired or learned abilities to understand, to think and to solve problems; they consider it largely determined by experience.

Many adherents of one side or the other, however, are repelled by the company they find themselves in: hereditarians by racists who maintain that the Negro is an inferior species of human being; environmentalists by those liberals who refuse even to consider genetic knowledge. As a result, psychologists often equivocate. One distinguished member of this discipline, who publicly is a convinced environmentalist, privately told me, "Arthur Jensen has done us a real service—we needed to pin down the genetic contribution." But Jensen himself, having argued at great length in print that racial I.Q. differences are largely inherited, states that he has never labeled Negro intelligence "inferior."

Some hard facts do, nevertheless, exist and are generally accepted. They are nearly all derived from I.Q. testing; for despite its limitations, it is still the only means we have of measuring intelligence. To date, no one has observed the actual phenomenon of thought taking place in the brain, nor seen any record of its having occurred. Physiologists know a fair amount about the brain—that it weighs about three pounds in the adult; that thought takes place in the cortex, a paint-thin outer layer of gray matter consisting of some 12 billion nerve cells, or neurons; that each neuron is almost, but not completely, connected to many other neurons at contact points called synapses; and that remembering, learning and problem solving involve the transmission of electrical impulses through the cells. At present, it is thought that the cell, when excited, produces a chemical, acetylcholine, that permits the electrical impulse to pass across the gap at the synapse to the next cell, exciting it, in turn; the moment the message has passed, however, another chemical, cholinesterase, destroys the acetylcholine and ends the transmission—all this within 4/10,000ths of a second.

A group of researchers at the University of California at Berkeley have been rearing bright rats and stupid rats, chopping off their heads and chemically analyzing their brains—and finding different ratios of acetylcholine to cholinesterase in the brains of the two strains. It may be that one ratio makes for faster transmission than the other: that is, faster thinking. But this still leaves many questions unanswered. Where and how is information stored and how is it drawn upon in the thinking process? Why are some men superb thinkers in some areas, such as music and mathematics, but not in others? Why have we never found any indication, under the microscope, of the "memory trace"—the record of permanent change due to learning or experience? Why is there no perceptible difference between the neurons of a genius and those of an idiot, those of the learned man and of the ignoramus, those of the dominant (operative) half of the brain and of the subordinate (unused) half?

But if we cannot yet observe intelligence directly, at least we can observe its effects in the form of intelligent behavior. This is why testing has been the principal source of information on the subject. It began 66 years ago, when the Ministry of Public Instruction in Paris commissioned psychologist Alfred Binet to design a test that would identify in advance the children who lacked the capacity to follow the regular curriculum and who should, therefore, be put in special schools. Binet's test consisted of numerous tasks and questions that graded those perceptual, verbal, arithmetical and reasoning abilities necessary for success in school; yet, it seemed obvious to him, and to most other psychologists, that he was measuring not only achievement but over-all intelligence.

Known in its various American revisions as the Stanford-Binet, it is still the most widely used individual intelligence test, although there are at least 40 others in print, including the well-known Wechsler-Bellevue test. All of them, however, are unsuited to large-scale use because they have to be given to one person at a time. Group tests, therefore, in which the subjects read questions to themselves and check off multiple-choice answers, have become a big business; there are close to 200 of them in print, with the Otis-Lennon Mental Ability Test (used in many schools) and the Armed Forces Qualification Test the best-known.

Originally, Binet scored each tested child as to his mental age, depending on how far the child got in the test compared with other children. But since a bright child might have a mental age of ten when he was only eight—and a dull one a mental age of ten when he was chronologically 12—the important figure was the ratio between mental age and chronological age; this ratio was his intelligence quotient, or I.Q. For the bright eight-year-old, it would be 10/8 (x 100 to get rid of decimals), or 125; for the dull 12-year-old, it would be 10/12 x 100, or about 83.

The tasks in all I.Q. tests are arranged in the order of their increasing difficulty. In the Stanford-Binet, for instance, three-year-olds are asked to do simple things such as building a bridge with three blocks or copying a circle. The four-year-old begins to get simple verbal and reasoning problems, such as "Why do we have cars?" or "Father is a man, mother is a——." The ten-year-old, in the (continued on page 106)Guide to Intelligence(continued from page 96) Otis-Lennon test, has to do much more advanced reasoning, involving questions such as this:

The opposite of easy is: hard slow tiresome simple shortor this:

Which number should come next in this series?

2 3 5 6 8 9? or this:

Questions for teenagers and adults are, naturally, even harder and call upon anywhere from seven different mental abilities to scores of them. In The Psychological Corporation's Multi-Aptitude Test, which is much like other tests of general intelligence, there are, for instance, items testing verbal ability, such as:

What word means most nearly the same as IMBUE: distort refute abstain inoculate allege

Others deal with quantitative (arithmetic) reasoning, such as:

Find the rule according to which this number series is formed, and write the next two numbers of the series: 5 –7 10 –14 19 –25 — —

Still others deal with abstract reasoning, such as:

These four figures are alike in some way:

Which one of these five goes with the four above?

("Inoculate" comes closest in meaning to imbue: the rule for the number series is—the difference gets larger by one each time, but also the sign changes every other time, hence the last two numbers are 32 and –40; figure 3 is the only one that goes with the set of four because it alone has more than four angles.)

Using various I.Q. tests, psychologists have learned that intelligence is "normally" distributed in the general population—that is, the great majority of people have I.Q.s of 100, give or take a few points. More than two thirds have I.Q.s between 85 and 115; less than three percent score under 70 and less than three percent score 130 or above. The former are the mentally retarded; the latter are the gifted.

Such statistics are helpful as guides to planning the size of the school system, institutions for the mentally retarded, manpower needs and the like. More important, they enable us to ask what makes for intelligence; for when we find out what kinds of people are at the upper end and at the lower end of the I.Q. curve, we may begin looking for cause-and-effect relationships. For instance, most of the people at the high end are in the higher socioeconomic strata of society and most of those at the low end are in lower and impoverished ones. Hereditarians, by and large, think that intelligent persons make their way to the upper levels, unintelligent ones remain behind or sink in the scale. Environmentalists feel that children of poverty—and especially of minority groups—never have a chance to develop their intelligence and that, moreover, I.Q. tests are built on middle-class values and do not give a fair picture of the talents of the poor.

Equally indisputable are facts about the average I.Q. of various ethnic groups—and equally moot are the explanations offered. Scots in the British Isles and Jews in America have higher average I.Q.s than the populations around them (Jews, for instance, run five to eight I.Q. points above the average of non-Jews in their same social and economic positions). Americans of northern-European origin average somewhat higher than those of southern-European origin. Oriental children, in some West Coast school surveys, come out consistently higher than white children. Why? Innate superiority? Social factors making for greater striving? The particular cultural tradition or kind of family life in which the child is reared? Every possible view has some adherents and some supporting data.

I.Q. is, as might be expected, as good a predictor of success in life as it is in school. The distinguished psychologist Lewis Terman followed a number of highly gifted children through decades of their lives; as a group, they turned out to be uncommonly successful in terms of career, social position, creative output, health, marriage and similar criteria. More generally, people with high I.Q.s tend to have careers of high social status and, indeed, careers that tend to require high I.Q.s: Ph.D.s have a median I.Q. close to 140; accountants, 128; lawyers. 127; salesmen and managers of retail stores, 116: auto mechanics, 102; farmers, 94; and teamsters, 89. (These are only averages; some farmers have scored as high as 147, some accountants as low as 94.)

The field of intelligence studies is full of curiosa of this sort. Here is a sampling:

• Despite all the clichés concerning the mental dullness of the criminal population, it seems to have about the same intelligence as the population at large.

• Males are consistently more intelligent than females, but only by a negligible amount—and only beyond the onset of adolescence; in childhood, girls score slightly higher than boys. In adulthood, though women score a little lower overall, they definitely surpass men in vocabulary and verbal fluency as well as straight memory: men are superior in arithmetical reasoning, mechanical aptitude and spatial relationships.

• Leadership among children, and probably among adults, is correlated with high I.Q., but only up to a point. When a person is 30 or more points brighter than most of the people in his group, he does not become a leader; it's anybody's guess why not. (There have been notable exceptions, however; Jefferson was evidently a highly intelligent man, and so were Churchill and Woodrow Wilson, among others.)

• Of all the measured similarities between man and wife, such as economic background, education and the like, the highest correlation is that of intelligence; spouses are even more alike in intelligence than brothers and sisters. Love evidently can't grow or survive where one lover is painfully dumb, or the other objectionably smart.

• The first-born child in a family is likely to be brighter than the last-born child by a little over three points. The difference could be due to the better intra-uterine or other biological advantages of being first in line; it might, however, be due to the greater attention and training first-borns get from their parents.

• Not all children of high-I.Q. parents are bright and not all children of low-I.Q. parents are dumb; in fact, on the average, children are part way between their parents' level and the average of the whole population.

• Creativity is not an automatic accompaniment of high I.Q.; in fact, some creative people have modest I.Q.s. A high I.Q. is essential for creativity in nuclear physics, mathematics and architecture; but numerous studies have shown that among painters, sculptors (continued on page 191)Guide to Intelligence(continued from page 106) and designers, the correlation between creativity and intelligence is, oddly enough, zero or even slightly negative. (This does not mean that highly creative artists are stupid: rather, they are all fairly intelligent, but among them the more creative are not necessarily the more intelligent.)

• Twins average four to seven I.Q. points lower than singly born children. The psychological explanation: They get less individual attention from their parents. The biological explanation: They had less room in the womb, hence got a poorer start.

• Children born of incestuous matings between brothers and sisters, or parents and their own children, have, on the average, considerably depressed I.Q.s, plus an inordinate number of physical ailments. The genetic explanation: Inbreeding increases the chance of inheriting the same recessive hidden defects from both parents, in which case they become dominant. The environmental explanation: Incestuous connections are most common among people of extremely poor social position and defective home life, both of which cripple the offspring. Perhaps both genetics and environment play a part. But in Japan, where cousin marriages are perfectly acceptable and occur in all classes, the children of such marriages average eight I.Q. points below children of comparable noncousin marriages. Here, at least, there is no choice of alternative explanations—only the genetic makes sense.

Such is the more-or-less solid ground in intelligence; all the rest is a slough of conflicting data and contradictory hypotheses. Environmentalists hold that intelligence tests do not measure "innate" intelligence, because there is no such thing. Dr. Alexander Wesman, director of the Test Division of The Psychological Corporation, maintains, "Intelligence is the summation of the learning experiences of the individual; that's what the tests measure and that's all they measure. It is possible that some people do have a greater neurological potential for learning than others, but I haven't yet seen it proved or disproved—least of all by the existing intelligence tests." Others are completely skeptical. Says Dr. Jack Victor of the Institute for Developmental Studies at New York University: "Intelligence tests measure a variety of subskills, but whether these, taken together, really equal intelligence is highly debatable. The subskilis are real, but intelligence may be a fictitious concept, a convenient label with which to refer to a number of disparate traits."

Hereditarians, however, insist that the tests do measure something innate and very real—an over-all potential capacity to learn, to recall, to discriminate, to think and to solve problems—and that this capacity deserves the name of intelligence. They admit that in most I.Q. tests, it is expressed through learned materials; but they insist that the "neurological substrate"—the individual's nervous structure and biochemistry—largely determines the ease with which he learns them and the effectiveness with which he uses them.

Variations in the neurological substrate are obvious enough, if one compares different species of animal. The brain of the worm is almost nonexistent, while that of the rat is well developed; the worm can learn only the simplest mazes; the rat, highly complex ones. But even within any given species, there are inherited differences in skeletal and body type, in excitability, in blood type, in hair color and the shape of the features, in the sensitivity to various pathogens; how could there not also be differences in the innate responsiveness and educability of the brain? Thus far, they have not been anatomically identified, but their presence is felt by every animal trainer and every teacher: Puppies of a given breed, children from very similar backgrounds, do not learn with equal ease or apply their training with equal success. In cloud chambers, physicists study unseen particles by means of the trails of droplets that condense along the paths they take; in I.Q. testing, psychologists study unseen innate intelligence by means of its effects on verbal, arithmetical and logical performance.

Some hereditarians go further; they argue that it is possible to measure "pure" or innate intelligence directly by omitting verbal and other culturally loaded materials and building tests around designs and shapes so familiar to persons of all classes and all cultures that learning is of no consequence. One such "culture-fair" test was constructed by Dr. Cattell (he of the two-g theory); it uses problems such as these:

Which one of these is different from the other four?

Which of the figures on the right goes in the missing square on the left?

(Number three is different from the other four. Figure two goes into the missing square.)

Dr. Cattell says that in countries as different as the U.S., India and Taiwan, his test has yielded quite comparable results, indicating that it is unaffected by culture and is, indeed, measuring innate intelligence.

The environmentalists maintain that such tests, even if they are really culture-fair, measure only very special abilities lather than the broad sweep of intelligence. Says J. P. Guilford (he of the three-dimensional matrix of 80 or more mental abilities), "In ruling out verbal tests, probably the most important aspects of intelligence have been lost." The Psychological Corporation used to publish Dr. Cattell's test, but gave it up, and Dr. Wesman explains: "We came to the conclusion that although such a test may use learnings common to different cultures and subcultures, it ignores the relevance of those learnings to survival and success. That being the case, it can hardly provide an adequate measure of intelligence."

But even if the standard I.Q. tests are the best measures of intelligence now available, and even if they do measure something genuine, those measurements are very frequently distorted by variables in the testing process. Taking a test, for instance, is more productive of anxiety for some people than for others, and anxiety decreases problem-solving ability. When Negro children from impoverished homes take an I.Q. test under the supervision of a neatly dressed white examiner, they are very likely to feel strange, awkward and uneasy—and consequently do not do as well as they might. Recently, psychologist Irwin Katz, of the Graduate Center at New York University, deceived black students taking an I.Q. test into thinking they were being tested merely in eye-hand coordination. Freed of anxiety, they registered significantly higher I.Q.s—and did better when the test giver was white than when he was black. Katz's explanation: Well aware of the low opinion most whites have of black intellectual ability, the blacks' motivation to do well on the I.Q. test was low. But when the test was disguised as something else, the desire to do well took over and scores improved. And the challenge to do well in the eyes of the white examiner was greater than for one of their own.

The Katz study is backed up by the findings of British psychologist Peter Watson, who tested black West Indian students in a London working-class neighborhood. When the test was identified as an I.Q. test, scores dropped by ten points. Watson is convinced that the variation can account for the average 15 points by which blacks fall behind whites in I.Q. tests—the basis for the claim that whites are, genetically speaking, superior intellectually to blacks. Interestingly enough, both Watson and Katz admit that heredity no doubt contributes to intelligence—but that the science of genetics is not advanced enough to state precisely how much. (Incidentally, even Arthur Jensen has reported that Negro children, when they feel at ease with the examiner, will score eight to ten points higher on an I.Q. test.)

Most important in the Negro subculture, when it comes to the matter of I.Q. testing, is the fact that grammar and vocabulary in common use are markedly different from those in white middle-class society. Moreover, Negro mothers in the more disadvantaged levels of society are not explainers, as are white middle-class mothers. Negro children may, in consequence, simply be unacquainted with the words, the grammatical usages and many of the elemental concepts (such as categorization) that are needed to think about the questions asked. A social worker in Watts satirically constructed the "Chilling Test"—a mock I.Q. test using only words and problems familiar to the Negro poor—and few middle-class whites who saw it could answer most of the questions correctly. So, too, a French-Canadian guide might score moronic on verbal ability and abstract reasoning, yet completely outclass his examiner at out-thinking wild animals or surviving in a midwinter storm.

For these and similar reasons, many of the findings of researchers on intelligence are contradicted by the findings of others. It is not just a matter of varying interpretations of the data; it is a matter of two or more studies of the same subject yielding different and even opposite findings.

Take the matter of intelligence and age. Various early studies indicated that it declines steadily from early adulthood onward. In the Thirties, for instance, researchers tested almost everybody in one New England town and found that the older the adults were, the lower they scored on reasoning ability. But whenever particular persons are tested and retested over a period of years, they show no such decline before the onset of senility; indeed, in one study a number of people were retested in middle age with an intelligence test they had taken 30 years earlier in college and got better scores in everything except arithmetic.

Just as bewildering is the case of our rapidly growing national intelligence. During World War Two, a large group of average soldiers took a test much like one given soldiers in World War One; if the 1917 standards for computing I.Q. had been used on their raw scores, they would have come out an average of 15 points higher than the World War One soldiers. The rise has continued: Since the end of World War Two, raw scores have gone up half as much again. What are we to think? Are the bright out-breeding the dull? Are we better informed because of improvements in education? Or have we merely become test-sophisticated; that is, skilled at getting better scores—but not any more intelligent than we were?

Assuming higher I.Q. scores would mean more than mere test-taking skill, the big question is: Can intensive education significantly increase the I.Q. in low-scoring children? Project Head Start, the nationwide Federally funded program of nursery-school experience for poor children, did not appreciably raise the school performance of the children involved—the I.Q. gains of five to ten points frequently reported for Head Start children did not hold up after the first year of regular schooling. But other efforts at compensatory education have used other techniques, and with more success: Colleagues of Dr. Deutsch at the Institute for Developmental Studies at New York University claim that their intensive-education experiments with, small groups of New York City Negro children have resulted in average I.Q. gains of nearly eight points in a year of three-hours-per-day schooling. Whether these gains will endure is not yet known; to judge by some similar experiments, once the children return to ordinary classrooms, the discouraging milieu of Negro slum life may make them lose interest in schooling and cause them to drop back.

Such preschool compensatory programs are designed to bring the underprivileged up to par with the rest of American society, but could early education also benefit those who already have normal advantages? Some experts think so and certain experiments in which preschool children have been taught to read and to use typewriters lend credence to their arguments.

But equally eminent psychologists, including Jean Piaget and the late Arnold Gesell, have been convinced that children cannot grasp certain problems until their neural organization is ready—and that the maturation of the neural system cannot be accelerated. In a typical Piaget test, when children under seven see water poured from a short, wide glass into a tall, thin one, they think it has become "more." Even though they can be persuaded to say that it is the same, they cannot be taught to feel that it is the same. Beyond the age of seven, however, they become educable on the matter. Similarly, though it takes a good deal of effort, children can be taught to read a year or two before first grade; but those who are not taught until several years later catch on so rapidly and easily that they soon are abreast of the early learners, and often have a more positive and joyous feeling about reading.

These are only facets of the unanswered central question: Is the individual's intelligence primarily a product of his perceptions, experiences and the influence of other persons upon him, or is his intelligence primarily determined by his genotype, the unique mixture of genes he has inherited from his father and mother?

Time and research have amassed impressive evidence on both sides. A very few examples will give some idea how thoroughly convincing each argument is, and how hopelessly contradictory they appear to be.

First, evidence for the supremacy of environment:

• In Israel, children of European-Jewish origin have an average I.Q. of 105, while those of Oriental-Jewish origin (Yemenites and other Mideastern Jews) have an average I.Q. of only 85, or borderline normal. But when both groups of children are brought up in a kibbutz, where they spend most of their time in communal nurseries run by dedicated nurses, both groups—according to informal reports by some observers—end up with an average I.Q. of 115.

• Some 30 years ago in Iowa, a small group of mentally retarded year-old orphans was experimentally placed in a hospital ward for feeble-minded women. In an orphanage, the children had had a minimum of individual attention; in the hospital, they were "adopted" by the feeble-minded women, who fed and bathed them, played with them and talked to them. In less than two years, their average I.Q. leaped from 64 to 94 and all had become good prospects for adoption. By the age of six, all were in adoptive homes, where they made small additional gains averaging two I.Q. points. Many years later, a follow-up found that they were almost all living normal married lives and that their own children had an average I.Q. of 105.

• Gypsy and canal-boat children in England, and Appalachian and Negro children in the U. S., have normal or near-normal I.Q.s when very young but drift downward thereafter. All four groups get a normal amount of stimulation at the infant level, but in childhood and the teens suffer "stimulus deprivation," because of their impoverished homes, their barren cultural surroundings and their poor school experiences. A number of studies show marked I.Q. losses for these various groups, averaging 20 to 30 points between their preschool years and their late teens.

To the environmentalists, scores of such studies seem proof positive that I.Q. is not genetically fixed and does not follow an inevitable course of development as do such traits as skin color and blood type.

Now, evidence for the supremacy of the genotype:

• First, recall what we learned earlier about the offspring of cousin marriages: Their average I.Q. is eight points lower than that of other children in their own socioeconomic class. The phenomenon has no explanation other than the matching up of recessive genetic defects inherited from both sides.

• Even when socioeconomic factors are reversed, Negro children do not surpass or even equal whites: Negro children born of parents in the highest of four socioeconomic groupings (the professional-managerial) average nearly four I.Q. points below white children born of parents in the lowest of the four groupings (unskilled labor). The over-all socioeconomic status of American Indian children is as poor (and perhaps poorer) as that of Negro children, yet the Indian children average seven or eight I.Q. points higher.

• Unrelated children reared in the same home ought to have very similar I.Q.s if environment were the dominant factor in intellectual development. But their I.Q.s show a correlation only half as large as that between real siblings reared in different homes. Similarly, the I.Q.s of foster children correlate more closely with those of their biological parents than with those of their foster parents.

• Identical twins have exactly the same complement of genes; when they are reared together, therefore, both their genotypes and their environments are substantially identical. Not surprisingly, the correlation between their I.Q.s is very high: Various studies report it close to the 90 percent mark. In a few score of known cases, however, identical twins have been separated soon after birth and adopted into different homes; if environment were the major factor in determining their I.Q.s, the correlation should drop almost to zero but, in fact, it remains very high. Even in different environments, identical twins grow up far more alike in I.Q. than ordinary twins reared in the same home.

Scores of such studies seem proof positive to hereditarians that biological endowment is a far more significant determinant of the intelligence of the individual than is environmental influence. They will admit, if pressed, that environment does affect mental development for good or ill in measurable ways, but having said so, they do their best to minimize its role, arguing that it accounts for 20 percent or less of the variance in I.Q. scores.

It seems obvious that one point of view must be correct, the other incorrect; but what seems obvious is not necessarily true. Most human phenomena are neither wholly good nor wholly bad, nor is a single doctrinaire explanation usually wholly true or wholly false. The truth lies not just in the middle but in a synthesis of the two sides. And so it is in the matter of intelligence. A unifying synthesis does exist.

It begins, as the noted psychologist I. I. Gottesman, of the University of Minnesota, points out, with the recognition that intelligence is not a lump sum, to which heredity contributes so many I.Q. points and environment the rest. The genotype and the environment do not add up, they interact—and the result is not a sum but a product.

But if we cannot separate the two interacting factors, at least we can ask how much difference it makes to modify one while keeping the other constant. We can ask, "Given any one genotype, how much can we modify the I.Q. by changing the environment?" And we can ask. "Given any one environment, how great are the variations heredity yields within it?"

As yet, there are no relevant research data that settle these questions for human I.Q.—but answers do exist for animals. Groups of genetically bright and genetically dull rats were reared in "restricted," "natural" and "enriched" environments, and then tested on maze-solving ability; various breeds of dogs were roared both indulgently and strictly, and then tested for their ability to obey a difficult command (not to eat). In both cases, the relative contributions of heredity and of environment varied for each combination of breed and rearing. For some breeds, changing the environment made little difference, while for others, it made a lot; and, conversely, within some environments, differences in heredity didn't amount to much, while within others, differences in heredity assumed considerable proportions.

Professor Gottesman believes that these results will prove to apply to human I.Q. and will make sense of what seem to be major contradictions in existing data. He offers the following diagram (from Handbook of Mental Deficiency, edited by N. Ellis) by way of illustrating the varying interactions (all of them speculative at this point) among a series of different environments and four hypothetical genotypes.

For genotype A, which might represent Mongolism, the "reaction range" is very narrow; that is, its various interactions with environments ranging from the worst to the best are all much alike, with a difference of only 50 percent or so between lowest and highest. For genotype D, which might represent hereditary genius, the reaction range is very broad; that is, its interactions with environments ranging from the worst to the best are very dissimilar, with a difference of some 300 percent between lowest and highest. Genotypes B and C are more nearly average and cover intermediate ranges.

Thus, it is clear that there is not one answer, not two answers, but a number of answers to the nature-nurture problem. It is clear, too, that both sides of the old argument have been right, and wrong, at the same time. For it is true that intelligence is the sum total of what has been learned—if we add: learned by a given mind, which can utilize its experiences only within its own biological limits. And it is also true that intelligence is a trait carried by the individual's genotype—if we add: as it develops in the environment available to it.

Applying this approach to the subject, we can make sense of many of the seeming contradictions in the existing findings. The contradictory results, for instance, of the intensive schooling of low-scoring children is not surprising: We have many genotypes being tested in many varied environments—and without anything like scientific control of either. Jewish children of two different backgrounds and I.Q. levels wind up, in a kibbutz, rising to the same higher level of I.Q.—but perhaps their genotypes were not really as dissimilar as one might suppose from their external traits. Negro and white children in the same schools, and even in the same socioeconomic class, remain widely separated, the Negro children being distinctly lower in I.Q.—but perhaps their environments were not really as similar as one might imagine. Negro and white children, even in the same schools and in the same socioeconomic class, do not actually have the same environment if, by environment, we mean the totality of the individual's experiences. Growing up black in a white society feels so different from growing up white in that society, even when class and income are equal, that we cannot fairly ascribe the remaining 10- or 11-point difference in I.Q. to heredity.

If Negroes were ever to experience thoroughgoing equality—social, economic and emotional—the average Negro I.Q. would very likely rise: perhaps only a little, still remaining distinctly below that of the white; perhaps enough for the two to coincide; perhaps enough to outstrip the white. We can't predict the outcome at this point, for blacks in America have never achieved genuine equality. Until they do, both those who say it will make no appreciable difference and those who are positive that all races have equal mental gifts are being demagogic in proclaiming as scientific fact ideologies that may be based on political sentiment.

What is tragic is that they are both serving vicious ends while pursuing noble ones. Jensen and the behavioral geneticists are carrying on legitimate and potentially very important research, but some of them—Jensen, in particular—have unscientifically extended their tentative and speculative findings into firm and fixed policy recommendations. Jensen, for instance, in urging special schooling for many Negroes on the basis of their supposedly irremediable inferiority, is going far beyond anything his own work justifies. Deutsch and other environmentalists, on the other hand, are also doing important research, but most of them are so powerfully moved by their own egalitarian feelings and their desire to help the underprivileged that they have tried to block the publication of pro-Jensenist papers and condemned all further research on the genetics of intelligence on the ground that whatever information it yielded would be "irrelevant" and "inflammatory."

Yet scientific inquiry and democratic progress are not, or at least need not be, antithetical. If the synthesis that resolves the nature-nurture controversy could be heard over the din of ideological battle, it might bring the two into harmonious alliance. Men did not learn to fly by ignoring gravity or denying that it existed but by learning the laws of aerodynamics and overcoming gravity. Men will make the most of their intelligence neither by denying the role of genetics nor by denigrating the importance of environment but by learning all they can about both and about the interaction of the two—and then applying the knowledge so as to give every man in society the maximum opportunity to develop his own potential.

Reproduced from Otis-Lennon Mental Ability Test, Copyright © 1967 by Harcourt Brace Jovan-Ovich, Inc. Reproduced by Permission.

Copyright © 1963 by the Mc Graw-Hill book Company. Reproduced by permission.