The Rising IQ Curve

The Rising Curve: Long-Term Gains in IQ and Related Measures, published by the American Psychological Association, 1998 with 23 contributors.

The Rising Curve covers three main topics in intelligence: Is there a world-wide trend in intelligence that is rising, is the gap between Blacks and Whites narrowing, and is there a dysgenic trend in genotypical intelligence?

The Flynn Effect: Rising IQs around the world

The observed increase in average IQ scores of 3 points per decade has been reported by many as proof that intelligence is not stable but is flexible with regards to environmental influences. However, none of the authors in this extensive review of the data, believes that intelligence is increasing at a rate greater than can be attributed by eugenic means (breeding smarter people). Instead, they are looking at the mechanisms of tests and how they are administered and interpreted in different time periods as people become exposed to differing environments. That is, as the humans change their environment they change the context in which their intelligence comes into play, and the testing methods must take this change into account. Obviously they have not because the generational change in IQ results has increased, without any evidence that today's children are any smarter than their great-grand-parents. So it is back to the drawing boards for the psychometricians who design the tests.

Neisser states that, "Whatever g may be, we at least know how to measure it. The accepted best measure, which has played a central role in analyses of the worldwide rise in test scores, is the Raven Progressive Matrices. This test, devised by Spearman's student John C. Raven, was first published in 1938 and is now available at several levels of difficulty. Arthur Jensen has said that Raven's test 'apparently measures g and little else' and that it 'is probably the surest instrument we now possess for discovering intellectually gifted children from disadvantaged backgrounds'. The Raven is of particular interest because it shows such large IQ gains over time. In The Netherlands, for example, all male 18-year-olds take a version of the Raven as part of a military induction requirement. The mean scores of those annual samples rose steadily between 1952 and 1982, gaining the equivalent of 21 IQ points in only 30 years! This amounts to a rate of no less than 7 points per decade -- a figure confirmed by data from many other countries. What can these increases mean?"

And later he states, "However, one may choose to interpret it, the fact that (unknown) environmental factors are raising the mean IQ of Americans by 3 points per decade certainly shows that the environment matters! The second proposition has quite a different status. Within a given population and a given range of environments (e.g., those that are characteristic for White American males in 1998), genetic factors do make a major contribution to individual differences. This has now been shown beyond a reasonable doubt by the methods of behavior genetics, a discipline that is primarily concerned with variability. The individuals in a given population differ on almost any measure one is likely to care about: their heights, weights, Raven scores, IQ scores, or anything else. Every such measure has a distribution, often a bell-shaped normal one. . . . Unfortunately, no one knows what it is about the environment that makes this contribution to differences in IQ scores. Some obvious possibilities, such as the economic and intellectual quality of children's home situations, may be less important than was once believed. The surprising fact is that when biologically unrelated children are raised in the same home (as in many cases of adoption), the correlation between their IQ scores is unimpressive in childhood and near zero as they grow up! This finding is important, but it is still negative: The aspects of the environment that do matter for the development of intelligence have not yet been identified."

Well, it doesn't mean that people are getting any smarter but rather that the environment is impacting how the results of IQ test scores are interpreted. That is, the expression of intelligence is not the same as intelligence. If children today have a high level of exposure to visual-spatial stimulus such as computer games, and IQ tests used 50 years ago used the same visual challenges to interpret intelligence, then the tests may no longer be valid from one generation to the next for comparisons. Intelligence hasn't changed, the means to test intelligence has not kept up with human contextual flexibility to deal with a changing environment.

Flynn states this fact succinctly, "Moreover, data whose quality cannot be challenged have posed the same question. The Dutch military data, like those of Israel, Norway, and Belgium, are near exhaustive; but even better, Vroon compared a sample of the total population of Dutch examinees with the scores of their own fathers. There is simply no doubt that Dutch men in 1952 had a mean IQ of 79 when scored against 1982 norms. Has the average person in The Netherlands ever been near mental retardation? Does it make sense to assume that at one time almost 40% of Dutch men lacked the capacity to understand soccer, their most favored national sport?"

Of course not, and that is why the Flynn effect is not taken seriously as an increase in real intelligence, because we just do not see one generation as more intelligent than previous ones, on a myriad of social indication scales. One would have to assume that the Greek philosophers were all mentally retarded, and yet wrote with such elegance that we still read and try to interpret their works today. It is absurd. And not one scholar in this book believes that real intelligence is changing but ever so slightly over time from environmental effects.

He goes on, "However, a careful survey of serious Dutch publications revealed not a single reference to a dramatic increase in cognitive ability or escalating giftedness among schoolchildren. The number of inventions patented in fact showed a sharp decline over the last generation (Flynn, 1987a, pp. 172, 187). . . . This means that in 1918, when scored against today's norms, Americans had an average IQ of 75 on tests in which the crystallized component is at least as great as that of the Wechsler tests. Does that mean that during World War I about half of White Americans lacked the capacity to understand the basic rules of baseball?"

This shows that over time, and a short time it is, we have not refined the tools to test intelligence longitudinally from generation to generation. That flaw no doubt will be addressed in years to come, but it is at present a problem that poses a vexing problem. But it in no way invalidates the conclusion that intelligence is real, it is primarily genetic, and matters in almost every aspect of human endeavor. And that is one of the primary reasons we know that increased scores are just that, an increase in scores and not in intelligence. There is absolutely no point in understanding intelligence with the vigor that we do if it did not contribute significantly to job performance, driving ability, voting sophistication, health, and a myriad of other social indicators. Intelligent people just plain perform much better than others when it counts. And there is no indication that these factors have been increasing over time due to an increase in real intelligence.

Environmental studies on nutrition have shown that vitamins or supplements have failed to reveal any impact on intelligence. How about education or some other mode of learning? Well, the data is confusing and circuitous. 48 states that, "The first subhypothesis, concerning better teaching of school-learned content, has already been falsified by the pattern of IQ gains over time. As I have shown, gains drop as one goes from Raven's type tests to performance tests to verbal tests to Wechsler subtests like Arithmetic, Information, and Vocabulary. This implies that the gains tend to disappear when material closer to the learned content of the school curriculum is tested. This leaves the second subhypothesis, namely, that schools are teaching better decontextualized problem-solving skills. Perhaps they are, but the hypothesis is empty unless (a) these school-taught skills are identified; (b) they are linked to the problem-solving skills used on IQ tests, particularly culture-reduced tests of fluid g; and (c) they are linked to some kind of real-world problem solving or, the greatest puzzle, it is explained why there is no such link. The very fact that children are better and better at IQ test problems logically entails that they have learned at least that kind of problem-solving skill better, and it must have been learned somewhere. However, simply to assert that the enhanced IQ test skill can be equated with some enhanced school skill is arbitrary and vacuous. The fact that education cannot explain IQ gains as an international phenomenon does not, of course, disqualify it as a dominant cause at a certain place and time. Particular countries are sometimes influenced by a factor that is culture specific. Comparing age cohorts has suggested that the urban Chinese gained 22 IQ points on the Raven Progressive Matrices between 1936 and 1986. Learning to read Chinese characters involves memorizing complex symbols, combining them to alter meaning and signal pronunciation, and taking such tasks seriously. The literacy that follows urbanization might be an important cause of matrices gains peculiar to China."

If nothing else, the above statement shows the confusion with the phenomena of IQ differences between generations, but it also shows that it does not occur where one would expect, in those skills that we have been pushing for years now to equip children to enter a more complicated workplace. That is, whatever the increase in intelligence scores mean, it DOES NOT translate into any hope of improving the expectations of today's children and young adults being better able to cope with our advanced technical society. The high test scores do not translate into smarter people. More than likely, the so-called increase in intelligence scores will be simply the training of visual symbol manipulation like the matrices gains of the Chinese above or some other stimulatory activity that impacts the tests scores, but not intelligence.

Another similar example might be transportation. Up until about 100 years ago, no one traveled at high rates of speed. Now, from trains, plains to automobiles, virtually everyone from a very young age is exposed to the phenomena of travelling at a relatively high rate of speed, impacting the motor sensory system that coordinates visual space with ones location. What if this simple training has an impact on some of the purer intelligence tests that use symbols? It has little value in most endeavors, but greatly impacts IQ test scores. Something as simple as this can throw a monkey wrench into looking at IQ differences from one generation to the next, while the tests are still able to differentiate very accurately cohort standings with relation to one another. That is the tests are valid but baselines must change with the population group being tested.

Flynn goes on to say that "Different kinds of IQ tests show different rates of gain: Culture-reduced tests of fluid intelligence show gains of as much as 20 points per generation (30 years); performance tests show 10 -- 20 points; and verbal tests sometimes show 10 points or below. Tests closest to the content of school taught subjects, such as arithmetic reasoning, general information, and vocabulary, show modest or nil gains. More often than not, gains are similar at all IQ levels."

Again, if the IQ gains had anything to do with education or with some groups being deprived of some of life's advantages, such as growing up in a lower SES family or other causes, then the gains would be disproportionately larger for these children and they would translate into improvements in educational performance. Neither of these is occurring as would be expected if the causes of rising IQs had anything to do with advantages of one group over another. Especially in light of the fact that the Flynn Effect is global and not isolated to specific cultures or locations.

Greenfield states, "To conclude, the Flynn effect is an example of the historical evolution of culturally phenotypic intelligence. It is not the evolution of 'general intelligence.' However, the fact is that general intelligence must always be instantiated in a specific cultural form. Culture takes general intelligence and makes it specific." What this says is that cultural changes are impacting the tests, and that the genetic component of intelligence, from 60~80%, is not changing. And the only way to test whether real intelligence is what it seems, an important indicator of how people deal with the complexities of life whether on a farm, in the jungle, or in a city, is to compare people within the context of that culture.

In addition, there has been no evidence that "within family" environmental influences have anything but a minimal impact on intelligence. What environmental influences there may be are "between families." In simple terms it seems smart kids get smarter because they hang around with smart friends, and dumb kids get dumber because they hang around with other dumb kids, and the selection is theirs, not their parents (this is a simplification of this hypothesis--see my web page for a lengthy discussion).

In conclusion, the Flynn effect means absolutely nothing with regards to holding out any hope that people are getting smarter and that somehow intelligence is not tied to our genes. The fact is, it is an academic question with regards to what causes it, what does it mean for psychometricians, and how will tests have to be modified in order to be able to compare IQ score variations from generation to generation. IQ tests for comparing differences in IQs within a cohort group are as good as we have and quite adequate and robust in repeatability and in predicting how well one can expect to do against the odds of life's challenges.

Is the gap between Blacks and Whites narrowing?

The second major issue in the book does not have any more definitive answers than the first, but the critique of this assumption may be easier. Several authors looked at the evidence, and simply put, there seemed to be a closing gap for a number of years from the 70s through most of the 80s that now is vanishing. What happened is the government stepped in an infused massive amounts of money to improve the test scores, using the National Assessment of Educational Progress (NAEP), as a guidepost for Black improvement. Had the government stepped in an infused the same amount of money into programs for gifted students, then surely the gap would have widened just as quickly between Whites and Blacks. All this has done is proven that if you throw a lot of money at a problem, and unequally at that, that you can change some test scores without changing the underlying abilities of those impacted by the program.

Hauser states "My favorite contribution to this literature is an elegant paper by Howard Wainer (1987). He showed that the uncertainty in SAT scores introduced by the average 12-14% nonresponse on the race-ethnicity question dwarfs the observed growth in minority SAT performance that occurred from 1980 to 1985. After observing the average verbal and math scores of White, minority-group, and nonresponding test takers, Wainer observed that if the scores of nonresponding test takers are the same as those of respondents of the same race or ethnic group, then it is possible to estimate the share of White and minority-group test takers among nonrespondents. Depending on whether one uses the verbal or math scores to make the estimates, this estimation procedure yields very different but rather high estimates of the share of minority-group students among nonrespondents. From 1980 to 1985, the estimated share of minority-group members among nonrespondents was never less than half and ranged as high as 70%, whereas the share of minority-group members was always estimated to be higher for mathematical than for verbal scores. The discrepant estimates invalidate the assumption that respondents and nonrespondents of the same ethnicity perform equally well, and the resulting uncertainty in test scores is larger than the observed changes in average test performance among minority test takers."

In just this one analysis therefore, the closing gap between Whites and Blacks is shown to be meaningless because of confounding effects, and for that reason the results are without any merit at all. And in a vindication of The Bell Curve that we are seeing more and more of in academic journals and books, Hauser states, "In one important respect, Herrnstein and Murray were surely right: It is most dangerous to project trend lines unthinkingly. Yet another set of NAEP assessments -- for 1992 -- became available after The Bell Curve went to press, and these data appear to confirm that the trend toward convergence in Black and White test scores was reversed after 1986-1988. For example, Figure 1 shows trends in the average (mean) NAEP scores of Blacks and Whites at age 13 in reading, science, and mathematics. The years of greatest convergence are not entirely clear because there are no reading scores for 1986 and no science or math scores for 1988. It does appear that sometime in the middle to late 1980s, the convergent trend ended, and Black-White gaps returned to levels of the early 1980s."

In summary then the following conditions led to a false indication that the intelligence gap between Blacks and Whites was closing when the government changed important programs as follows:

-- Educational expenditures went up much faster for Black students than for all students being tested.

-- Back to basics programs emphasized "teaching to the test" to improve scores so that Black students could do better on the standardized exams.

-- An end to social promotions increased absenteeism and the drop-out rate, so that these marginal or low intelligence Blacks were no longer tested and included in the averages.

-- More students were enrolled into special education programs (slow learners) which was dominated by Blacks and these students also were not included in the NAEP test score results.

Finally, Ceci, Rosenblum and Kumpf state, "THE ESTABLISHED FACTS: There is no dispute among psychometric researchers that Whites outscore Blacks on IQ tests as well as on standardized achievement tests. The gap most commonly reported is approximately 1 SD. (On the most widely used individual IQ tests, this translates into a 15- to 16-point gap between Blacks and Whites; Hispanics fall midway between these groups, and Asian Americans score about 3 points, on average, higher than Whites.) Racial and ethnic gaps in IQ and achievement tests scores have existed throughout this century; for example, IQ differences between Blacks and Whites were evident on the first Stanford -- Binet IQ test normed in 1932. Even earlier signs of a racial gap of approximately 1 SD were apparent on the Army Alpha tests administered to recruits during World War 1. These facts are not in dispute among researchers, although their interpretation is open to argument."

Are we in a dysgenic or eugenic breeding trend?

Environmental changes as we have seen can change culture quickly with regards to learning, attitudes, skills, moral values, etc. But the genetic makeup of humans changes vary slowly under most reproductive conditions though it can become rapid under conditions of immigration, war, or some other major impact on the frequency of a population's genes. So the question arises, is the population of the United

States increasing in genetic intelligence or decreasing? The final section of this book deals with this issue, and the metaphor is that it appears we are seeing the effects of a sinking ship in a rising pond. That is, we are better educated but the genetic capital of our population may on the decline, which of course will lead to a decline of the nation itself. But the data is extremely difficult to interpret and inconclusive. I would only add that genetic changes are far more important than environmental changes because they are much longer lasting and intractable. That is for better or for worse, the nation is pretty much stuck with the genes found in its population. And competition with other nations will depend of the quality of these genes over the long run.

Lynn concludes that, "Four types of data indicating an inverse relationship between intelligence and fertility have been presented. There is evidence for an inverse relationship between (a) SES and fertility, (b) intelligence and number of siblings, (c) intelligence and fertility, and (d) educational level and fertility. All four lines of evidence point in the same direction and to the same conclusion: Fertility has been dysgenic in the economically developed world since the early decades of the 19th century and in most of the economically developing world during the 20th century. The data showing an inverse association between SES and fertility go back to the cohorts born in the second quarter of the 19th century. This means that dysgenic fertility has been present for about five generations. Retherford and Sewell's (1988) American study indicated that the genotypic decline was 0.64 IQ points for the generation born in 1940. If this figure is projected back for five generations, it can be concluded that American Whites have suffered a genotypic decline of 3.20 IQ points over the five generations. This is almost certainly an underestimate because dysgenic fertility was considerably greater in the earlier generations than among the 1940 cohort from which the figure of 0.64 IQ points is derived. When this is taken into account, the magnitude of the deterioration of genotypic intelligence in the United States appears to have been about 5 IQ points since the early 19th century. Dysgenic fertility has probably produced a similar deterioration in Europe, considering that dysgenic fertility in relation to SES was present in the early 19th century and that the magnitude of the inverse relationship between intelligence and fertility has been about the same. In the economically developing world, such as the Latin American countries represented in Table 6, dysgenic fertility is very strong, but has probably not been in place for so long. The proposition that the genotypic intelligence of modern populations is deteriorating is not directly verifiable but is an inference derived from two premises: the inverse relationship between intelligence and fertility, and the heritability of intelligence. Because the two premises are solid, the inference appears to be solid. Recently, however, the inference has been challenged by Preston and Campbell (1993), who claimed to demonstrate that dysgenic fertility is compatible, after some generations, with a stable population IQ. Preston restates this argument in the present volume (chapter 15). In my opinion, the argument is flawed, for the reasons given by Coleman (1993) and Loehlin. If Preston and Campbell's argument were correct, natural selection by differential reproductive fitness would not work, and the fundamental theorem of biology since the publication of Darwin's Origin of Species would be overthrown. I do not believe that biology is ready for such a drastic paradigm shift. The dysgenic fertility and consequent deterioration of genotypic intelligence that have been in place since the second quarter of the 19th century have been accompanied by environmental improvements that have brought about rises in phenotypic intelligence. It can be predicted that the environmental improvements will in due course show diminishing returns and peter out. If dysgenic fertility is still present when this point is reached, it can be anticipated that phenotypic intelligence will start to decline. Insofar as the maintenance of a high level of civilization depends on the intelligence of its population, the quality of U.S. civilization will also deteriorate. It is a curious fact that the evidence pointing to this conclusion has received no mention in contemporary textbooks of psychology and sociology."

I would like to add two final points to eugenics and to alterations in the variance of the standard IQ bell curve: "assortative mating" and "grandparent effects." With universal education there seems to be more of a trend for intelligent people to marry each other. That is, the filtering process brought about by separating groups into trade schools, universities or the factory floor for social interaction leads more and more to likes marrying likes, and this especially includes intelligence because more than any other trait it determines what type of educational program and job you will be part of.

In addition, as people take greater care in making sure that their children will be endowed with the very best genes, more emphasis will be placed on what is known as the "grandparent effects." That is, when choosing a mate, I want to make sure that the genes my wife carries are the very finest possible. The best way to determine if our children will be intelligent with regards to her contribution will be to look at her family tree and not just her intelligence. Does she come from a long line of prosperous, successful and intelligent relatives, or is it random? Were all four grandparents intelligent? Are her siblings and cousins mostly intelligent or are they highly variable?

More and more, this type of information allows people to make highly salient decisions regarding mate selection, and may lead to a class of people who are far above the rest of society in innate intelligence. In fact, this very technique as reported by MacDonald (see my web page) has been used by Jewish families for thousands of years to select the best mates. Now that it is common knowledge to any well educated person, the techniques can be applied by a far greater number of people, and could lead to a secular eugenic religion where the genetic quality of the children becomes foremost in a families fertility practices as part of their value system. To have the best, you must breed the best or "you can't make a silk purse out of a sows ear."

The above review of "The Rising Curve" is highly biased. If you don't agree with it, read the book and write your own highly biased review.


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