The Mismeasure of Samuel Morton and Psychometrics and the Myth of Multiple Intelligences

Stephen Jay Gould, The Mismeasure of Man (London: Penguin, 1981)

Stephen Jay Gould’s ‘The Mismeasure of Man’ is an almost entirely scientifically worthless work which has nevertheless proved enormously influential, in scientific discourse, social science discourse, political discourse and among the wider educated public.

Gould’s central argument is that objective, disinterested scientific research on sensitive and politically charged subjects, such as intelligence differences, and differences in brain size, as between groups and individuals, is almost impossible, because such research invariably reflects and is corrupted by the social and political biases of scientists themselves, and of the wider culture in which they live and work and were raised.[1]

Ironically, the closest he comes to actually proving this thesis is through his own work, which manifestly reflects the egalitarian, Marxist, radical leftist political milieu in which Gould was, by his own account, raised, as well as the racially egalitarian ideology prevailing in the wider American society in which his work, and this work in particular, was assiduously championed and promoted in academia and the media.[2]

‘Debunking Scientific Fossils’

Celebrated educational psychologist Arthur Jensen, himself a main target of Gould’s invective, and one of the few such targets still alive and hence able to defend himself at the time Gould published his book, wrote a devastating review of Gould’s book in the journal Contemporary Education Review soon after the book was published, which I strongly recommend reading in conjunction with Gould’s work as a necessary corrective to the latter’s errors and misrepresentations.

Jensen titled his review, ‘The Debunking of Scientific Fossils and Straw Persons’ (Jensen 1982).

This reference to ‘scientific fossils’ had, one presumes, a double meaning. First, it was a reference to Gould’s background as a palaeontologist.

Second, and more importantly, it was a reference to the fact that most of the research that Gould purports to debunk was conducted decades, even centuries, before Gould’s own work was written.[3]

It therefore almost totally irrelevant to assessing the merits of contemporary research in psychometrics, intelligence research and behaviour genetics, research which, save for his attack on factor analysis and the g factor (see below), Gould almost entirely ignores.

As Jensen puts it:

“Instead of taking on the real issues of contemporary research in these fields, paleontologist Gould tilts at a museum collection of scientific fossils” (Jensen 1982: 124).

In focussing almost exclusively on nineteenth and early twentieth century research in craniology and psychometrics rather than the latest cutting-edge research, Gould’s implication seems to be that, since such early research was, at least in Gould’s own telling, invariably crude, methodologically flawed and beset with statistical errors and fallacious thinking, the same must necessarily be true of all modern research in the same fields.

Yet this is a fallacious assumption, as must be obvious to anyone with a remote familiarity with the history of science, or the nature of scientific progress and the scientific method.

In short, science is a cumulative self-correcting process, both building on and supplanting what has gone before but also often invalidating it, through a method involving the testing and falsification of hypotheses.

As Arthur Jensen himself puts it in his review:

“Should we ridicule the early astronomers for claiming that the earth is the center of the universe, or the early anatomists for claiming that the heart is the seat of emotion?… Gould’s exclusive critical focus on forebears (and the worst examples, at that) is much like trying to condemn the modern automobile by merely pointing out the faults of the Model T” (Jensen 1982: 125).

In short, if we today see further than previous generations, it is, not just through ‘standing on the shoulders of giants’, but also through trampling on the corpses of midgets.

Defaming the Dead

However, to say this is to impliedly concede that Gould’s critique of nineteenth and early twentieth century work in craniology, and early work in intelligence testing, is largely valid. This, however, is questionable.

Indeed, one suspects that Gould chose to debunk early research in psychometrics and anthropology, rather than the latest cutting-edge research, not only because, since science is a cumulative, self-correcting process, the former is almost inevitably weaker and hence more amenable to legitimate criticism, but also because few of the scientists whom he critiqued were around to defend themselves and point out Gould’s own errors and misrepresentations in his characterization of their work.

Therefore, most readers would simply take Gould’s assertions about nineteenth century craniologists and early-twentieth century pioneers in intelligence testing on trust.[4]

Yet, interestingly, in the years since Gould’s work was published, a few bold intrepid researchers with too much time on their hands have indeed taken the trouble to track down and reread some of this literature, just as Gould himself claimed to have done.

Unfortunately, however, their conclusions regarding the content and merits of this research have often diverged dramatically from those of Gould himself.

Indeed, they have found that work conducted over a hundred years before that of Gould himself, in an age before the Modern Synthesis, before the discovery of DNA, and before even Mendel’s work on inheritance and Darwin’s on evolution, when science itself was still very much in its infancy, and conducted by the very scientific pioneers that Gould himself chose to posthumously defame, was often methodologically and mathematically superior to that of Gould himself, and moreover conducted with greater scientific integrity and disinterest.

The Mismeasure of Samuel Morton

In writing this, I allude in particular to the Gould’s critique and purported reanalysis of the data of Samuel Morton, a pioneering and once celebrated early craniologist and anthropometrist, who is regarded as both the founder and leading exponent of what was once called ‘the American School of Anthropology’, yet who is today largely forgotten, and chiefly remembered, to the extent that he is remembered at all, primarily on account of Gould’s critique.

Morton, famous for his collection of human skulls, the largest such collection in the world at that time he lived, which he had accumulated from all around the world, sought to measure and compare the cranial capacity of the various skulls by a technique that involved filling the various skulls with material such as seed or, later, lead shot, then moving the seed or shot to a different container in order to measure its volume.

Gould, however, purports to show that, despite the seeming objectivity of his methodology, Morton nevertheless systematically underreported the average cranial capacity of non-white skulls, while systematically overrepresenting that of white Caucasian, and especially white Nordic, skulls, on account of his own supposed “unconscious finagling” (p55).

Thus, Gould gratuitously speculates:

“Plausible scenarios are easy to construct. Morton, measuring by seed, picks up a threateningly large black skull, fills it lightly and gives it a few desultory shakes. Next, he takes a distressingly small Caucasian skull, shakes hard, and pushes mightily at the foramen magnum with his thumb. It is easily done, without conscious motivation; expectation is a powerful guide to action” (p65).

“I detect no sign of fraud or conscious manipulation. Morton made no attempt to cover his tracks and I must presume that he was unaware he had left them. He explained all his procedure s and published all his raw data. All I can discern is an a priori conviction about racial ranking so powerful that it directed his tabulations along preestablished lines” (p69).

Unfortunately, however, two subsequent reanalyses of Gould’s own reanalysis found little if any evidence for any such finagling, conscious or unconscious, at least on the part of Morton (Michael 1988; Lewis et al 2011).

On the contrary, the authors of the most recent and rigorous of these reanalyses found that virtually all the errors were on the part of Gould, not Morton, and, whereas Morton’s errors seem to have been random in their direction, and hence not obviously reflective of any biases on the part of Morton, Gould’s errors all had the effect of minimizing the reported racial differences.

The authors conclude:

“Ironically, Gould’s own analysis of Morton is likely the stronger example of a bias influencing results” (Lewis et al 2011).

In contrast, whatever biases or preconceived notions Morton may have had regarding either the intellectual ability or cranial capacity of different races, which is itself a matter of some dispute, Morton evidently did not allow them to influence either his measurements or how he reported his results.[5]

Thus, the authors conclude:

“Rather than illustrating the ubiquity of bias, [Morton’s research] instead shows the ability of science to escape the bounds and blinders of cultural contexts” (Lewis et al 2011).

Of course, it might be suggested that, just as I criticise Gould himself for critiquing the work of dead scientists no longer able to defend their own work, the same could be said also of Lewis et al (and perhaps of myself), since Gould too had died a few years before their paper was published.

However, an earlier analysis published in the journal Current Anthropology reported similar conclusions well over a decade before Gould’s death, yet the latter, to my knowledge, never deigned to acknowledge, let alone respond to this critique (Michael 1988).

Moreover, lest anyone dismiss this analysis on the same grounds that Gould dismissed the earlier work of Morton himself, namely by suggesting that the findings reflected only confirmation bias, or the racial prejudice of the author and researcher himself, it ought to be noted that the author of this earlier study was certainly no racist, nor even a race realist, emphatically rejecting the very biological validity of the race concept, let alone the notion of race differences in brain size.[6]

Yet he nevertheless concludes:

“Morton’s research was conducted with integrity” (Michael 1988: 353)

The contrast with Gould’s own work is, of course, striking.

Brain Size and Intelligence

The odd notion that brain size is unrelated to differences in intelligence enjoys surprisingly wide currency. I suspect this idea originates with Gould’s book, and the latter is indeed, my experience, sometimes cited as authority for this claim.

In fact, however, Gould, in his defence, makes no such claim.

Gould is, after all, a palaeontologist, and no remotely competent palaeontologist would deny that the massive increase in hominid brain size that occurred during the course of human evolution is related to our superior intelligence as compared to other species.

After all, brain tissue is hugely metabolically expensive and larger brains would hence never have evolved unless they conferred some compensating advantage, presumably intellectual.

As well as being related to intelligence differences as between different species, brain size is also correlated with differences in IQ as between individuals (Pietschnig et al 2015; Rushton and Ankney 2009).

Indeed, by so strenuously attempting to refute and discredit the research of figures like Morton, whose research demonstrated an association between brain volume and racial ancestry, Gould might even be taken as implicitly conceding that brain volume is indeed likely related to intelligence. Otherwise, he would have had no need to so strenuously and mendaciously attempt to dispute in their findings.[7]

Instead, rather than outright denying that there exists any association between brain-size and IQ, Gould instead acknowledges that brain size may indeed correlate with IQ, but argues that, rather than being causal, this is a consequence of the superior material conditions of children from economically privileged backgrounds, which enables them to both better achieve their full intellectual potential and also to grow bigger brains.

Thus, in a passage from the ‘Postscript’ to his chapter on nineteenth century craniology (‘Measuring Heads’) included in his original 1981 edition of ‘The Mismeasure of Man’ that is oddly omitted from the later “Revised and Expanded” edition, Gould argues:

“The primary environmental hypothesis for correlations of head size with social class holds that they are artifacts of a causal correlation between brain size and status. Large bodies tend to carry large heads and proper nutrition and freedom from poverty fosters better growth in childhood” (p111).

Thus, he explains:

“Brain size would then be an imperfect measure of height and IQ might correlate with it… for the primary environmental reason that poverty and poor nutrition can lead both to reduced stature and poor IQ scores” (p108-9).[8]

This seems superficially plausible.

Severe malnutrition during childhood is indeed associated with reduced IQ and reduced stature, and presumably reduced brain size too (Soliman et al 2021; Kirolos et al 2022).

Indeed, malnutrition and disease were indeed surely a factor in explaining reduced stature among the poor in previous centuries, and surely remain a factor in explaining the reduced stature, brain size and measured IQs of many people in the developing world today.

However, this explanation cannot explain the association between brains-size and IQ in the west today, since the sort of extreme poverty and undernutrition that results in reduced stature and brain growth is now all but unknown in the west.

Indeed, in the west today, obesity is a far greater health problem in the west than is undernutrition, even among the poor.

Indeed, it is a problem especially among the poor. Thus, at least in the developed world, obesity is actually more common among those of lower socio-economic status than it is among the wealthy (Zhoi 2021; Kim & von dem Knesebeck 2018).

Moreover, while height does indeed correlate with measured IQ, the correlation of brain size with IQ is stronger than that observed for height.[9]

So, reduced brain-size cannot be solely a result of malnutrition or poverty unless these factors, for some reason, reduce brain size to a greater extent than they do overall stature.

Moreover, even within a single family, the sibling with the larger brain tends to have the higher IQ, which suggests that differences between families, including in socioeconomic status and nutrition, cannot be the explanation for this association (Jensen & Johnson 1994; Lee et al 2019).

IQ Testing

Whereas the first part of Gould’s book deals with the nineteenth century science of craniology, the second half ostensibly focuses on intelligence testing.

Again, however, he focuses largely on early research, focussing on the work of early pioneers in intelligence testing, such as Alfred Binet, Lewis Terman, Cyril Burt, Goddard, and Yerkes, and the methods used to test the ability of US military recruits during World War I. This work was mostly conducted in the early twentieth century, when IQ testing was crude and still very much in its infancy.

Thus, Gould’s critiques of the supposed methodological and statistical errors of these early pioneers may or may not be valid, but they are, like his critique of eighteenth and nineteenth century craniology and anthropology, almost entirely irrelevant to an assessment of the modern science of intelligence testing.

To the extent that Gould does critique of modern intelligence research, he focuses almost entirely on two related issues – first, the statistical method of factor analysis as employed by psychometricians, and, second, the concept of a general factor of intelligence (‘g’) as revealed by this method of statistical analysis.

The g Factor

The so-called ‘g-factor’ is a concept invoked to capture the positive correlation between performance on virtually all different types of test item on intelligence tests, even those measuring very different forms of intellectual ability.

In short, people who score high in one form of intellectual ability (e.g. verbal ability) also tend to score high in other forms of intelligence (e.g. spatial ability), while those scoring lower on one type of test item likewise tend to score lower on other types as well. The ‘g-factor’ refers to this general factor of intelligence, which explains most of the variation in IQ test performance as between both individuals and groups.

In itself, the g factor is, as Gould himself repeatedly emphasises, only a statistical construct. Yet Gould contends that, by treating ‘g’, or general intelligence, as a real thing, psychometricians commit what he refers to as the ‘fallacy of reification’.

This all sounds very impressive, but what exactly does Gould mean by the ‘fallacy of reification’?

After all, if performance on different types of test item, even those with very different content and testing very different types of ability, do indeed consistently correlate, then there must surely be some sort of explanation for this.

Moreover, while ‘g’ itself is indeed a mere statistical construct, it nevertheless itself correlates with measures of real physical and structural differences in the brains of different individuals, including with differences in cortical thickness, neural efficiency and glucose metabolism, functional connectivity, nerve conduction speed, white matter integrity, regional grey matter volume – and, of course, as already discussed, brain size.

For all his obfuscations, Gould’s critique of the g factor ultimately seems to come down to two points.

First, he reiterates the famous admonishment that ‘correlation does not imply causation’.

Therefore, Gould argues, even if performance in different spheres of intelligence do strongly correlate with one another, this does not necessarily mean that we can posit a general factor of intelligence that causes this correlation.

However, while it is indeed an axiom of scientific research that ‘correlation does not imply causation’, nevertheless, if the performance of different individuals on different types of intelligence test item do indeed consistently correlate with one another, then, again, there must be some sort of explanation for this.

Thus, while it may be true that ‘correlation does not imply causation’ in the sense of either A causing B, or B causing A, or indeed even A and B both being caused by C, nevertheless, if two variables (A and B) do indeed consistently correlate and the finding is robust and well-replicated, then this does indeed imply some sort of causal nexus, howsoever distant and indirect.[10]

Indeed, Gould himself comes close to admitting this in his second point, namely that, even if the g-factor is a real thing, it is not necessarily a heritable thing, but could instead reflect environmental factors.

Thus, he rightly recognises, “we cannot infer the cause from the correlation” and, seemingly admitting the existence of g, at least as a statistical construct, contends that, rather than “reflect[ing] an inherited level of mental acuity”, it could instead “record… environmental advantages and deficits (some people do well on most tests because they are well schooled, grew up with enough to eat, books in the home, and loving parents)” (p252).

In other words, contradicting his first point, Gould now seems to be conceding that correlation does indeed imply causation, at least in this case, but that the cause is to be found, not in genes, but in environmental factors.

“If the simple existence of g can be theoretically interpreted in either a purely hereditarian or purely environmentalist way, then its mere presence—even its reasonable strength—cannot justly lead to any reification at all” (p252).

Gould is right that, even if the different components of intelligence do intercorrelate (and they do), this does not necessarily mean that the reason for this correlation is to be found in heredity.

However, a great deal of evidence (e.g. from twin studies and adoption studies) does indeed suggest that heredity plays a large role in explaining differences between individuals in g.

Yet, besides dismissing the data on identical twins reported by Cyril Burt as fraudulent and hence worthless, Gould says almost nothing about his large body of research – research which has, incidentally, entirely corroborated the supposedly fraudulent and worthless findings of the much-maligned Burt.[11]

The g Factor and Heritability

In arguing that, if the g factor does exist, then it could just as easily be caused by environmental factors as by heredity, Gould gets one thing right – namely, he recognises that the question of whether individual variation in IQ scores is usefully captured by a single g factor is an entirely separate one from that of whether differences in intelligence, howsoever they are best represented in terms of their underlying factor analytic structure, are substantially heritable.

Yet, elsewhere, he seems to confuse these two questions, namely heritability and factor analytic structure, seeing the question of the existence of ‘g’ as somehow, and for some reason, inextricably connected to that of heritability, with theories of the heritability of intelligence necessarily depending on the unitary structure of intelligence.

Thus, he writes:

“I will at least say this for Arthur Jensen. He recognizes that his hereditarian theory of IQ depends upon the validity of g” (p265).

It may indeed be true that Jensen’s own specific “hereditarian theory of IQ depends upon the validity of g”, since Jensen did indeed devote much of his distinguished career to studying the nature of the g factor.

However, it is not true to say that hereditarian theories of IQ in general depend on the existence of a g factor.

On the contrary, if, as Gould has claimed, the g factor could be caused by environmental factors, then is it not also true that the multiple intelligences posited by fringe scholars like Howard Gardner could themselves be substantially heritable?[12]

In short, there is no reason to anticipate that multiple independent factors of intelligence, were they shown to exist, would be any less heritable than a general factor of intelligence.

Thus, Gould comes close to contradicting himself thrice over: first, he denies the existence of the g factor, contending that correlation does not prove causation; next, he admits that maybe the g factor does exist, but contends that the existence of the g factor says nothing about whether it is caused by genetic differences or environmental factors; then, contradicting himself yet again, he says that hereditarian theories of IQ necessarily depend on the existence of the g factor.

Group Differences and the g Factor

With respect to the vexed question of innate group differences, Gould again sees the g factor as central, writing:

“A reified Spearman’s g is still the only promising justification for hereditarian theories of mean differences in IQ among human groups” (p320).

Yet, here, he is again confused, for different “human groups” could conceivably differ in their innate intellectual ability, even if intellectual ability is itself not a unitary construct, but rather captured by several independent factors of intelligence (e.g. spatial and verbal ability).

For example, one group might score higher than another in verbal ability, while the other group scores higher in spatial ability, and these differences in ability could be innate in origin.[13]

Indeed, there is a particular irony here, because, in fact, the more different independent factors of intelligence that we recognise, then the less likely it becomes, on purely statistical grounds, that different races would nevertheless, purely by chance, have evolved to perform exactly equally in every single one of these different domains.

Thus, it is perfectly possible, if somewhat unlikely, that two races, say blacks and whites, that evolved on separate continents, in sufficient reproductive isolation from one another (and, presumably, subject to sufficiently divergent selection pressures) as to have evolved the obvious, and not so obvious, physiological differences that distinguish these two races, might nevertheless, purely by chance, have evolved exactly equal levels of innate cognitive ability – if cognitive ability is indeed usefully characterized as a single unitary factor, namely ‘g’.

However, the more different domains of intelligence that we recognise, each supposedly statistically independent of each of the others, then the correspondingly less likely it becomes that any two races would be equal on every single one of these independent factors.

If, like Howard Gardner, we posit as many as seven, or, in later expositions of his theory, as many as eight or even nine different ‘intelligences’, then it becomes statistically extremely unlikely that two different races, would, purely by chance, have evolved to be exactly equal on every single one of these different allegedly independent factors of ability.

When, on the other hand, one broadens one’s gaze to all the different races and populations in the world, the notion that all these different races and populations might have evolved exactly equal levels innate ability in all seven, or all eight, or all nine, of these supposedly independent spheres of ability is all but unthinkable on statistical grounds alone.[14]

Thus, far from ‘g’ representing, as contended by Gould, “the only promising justification for hereditarian theories of mean differences in IQ among human groups”, in fact a unitary g factor represents the best case scenario under which it is possible, but still unlikely, that different races might conceivably have evolved almost exactly equal ability.

Even then, however, it would remain extremely unlikely that this would apply to every single race or population on the planet.

It is therefore a supreme, yet rarely acknowledged, irony that Gould, a famously fervent opponent of the notion that different races differ in intellectual ability, whose abhorrence of this notion is such that it seems to have formed the main impetus for his authoring the very book I am currently reviewing, should nevertheless, in this very same book, have also so vehemently opposed the existence of the g factor that is so firmly established by modern psychometric research, since the positing of such a factor is surely the most likely scenario under which complete equality of the races in intellectual ability, an unlikely scenario under the best of conditions, could most plausibly be supposed to have evolved.


[1] Thus, Gould writes:

“I criticize the myth that science itself is an objective enterprise, done properly only when scientists can shuck the constraints of their culture and view the world as it really is” (p21).

Here, he skirts dangerously close to the anti-scientific epistemologically nihilistic cultural relativism of postmodernism, though, as a working scientist, necessarily ultimately rejects this view.
Gould is, of course, correct that scientific research does not occur in a social, cultural or political vacuum.
Scientists are not only well aware of the social, political and cultural values and dogmas prevailing in the wider society in which they live and work, they also typically share these values themselves, having, like non-scientists, internalized these values themselves during the process of socialization. It is therefore unsurprising that many biologists who should know better nevertheless parrot the biologically untenable leftist dogmas of sex denial, race denial and biology denial.
Moreover, even those scientists able to see that these dogmas are biologically untenable, not to mention empirically unsupported, are well aware of the fate that has befallen other scientists courageous or foolish enough to challenge the conventional wisdom with regard to these subjects (e.g. Helmuth Nyborg, Bo Winegard, Noah Carl, Bryan Pesta, even Lawrence Sommers and James Watson), and therefore know only too well to either parrot conventional dogmas themselves or else keep their mouths firmly shut on these matters if they want to keep their jobs.

[2] In referring to “egalitarian, Marxist, radical leftist political milieu in which Gould was… raised”, I refer to Gould’s own admission, “I learnt my Marxism at my daddy’s knee”. I make feel the need to clarify this since Gould often accused critics who suggested his Marxist upbringing and leftist views may have influenced his scientific views of “red-baiting” (e.g. here). Yet, as we have seen, the idea that a person’s political and social views influence their scientific claims is among his central claims in ‘The Mismeasure of Man’. Are leftists like Gould himself, then, in Gould’s view, somehow exempt from this sort of bias? Or is it just distasteful to accuse them of it? Gould’s resort to the charge of is “red-baiting” particularly ironic, not to mention hypocritical, given his own rather distasteful attempt, in ‘The Mismeasure of Man’, to smear hereditarianism by reference to its supposed association with Nazism, segregation, slavery and eugenics.

[3] Although Gould’s ‘The Mismeasure of Man’ was first published in 1981, nevertheless, according to Jensen’s count:

“Of all the book’s references, a full 27 percent precede 1900. Another 44 percent fall between 1900 and 1950 (60 percent of those are before 1925); and only 29 percent are more recent than 1950” (Jensen 1982: p124).

Gould, for his part, defends his decision to focus on nineteenth and early twentieth century research, by writing:

“I have said little about the current resurgence of biological determinism because its individual claims are usually so ephemeral that their refutation belongs in a magazine article or newspaper story. Who even remembers the hot topics of ten years ago[?]” (p28).

This is, of course, true, if one’s knowledge of, and interest in, science is restricted to the latest sensationalist stories being written about in the press, talked about on television or currently trending on social media. However, serious scientists are interested in the latest research irrespective of whether findings are being reported upon, or attracting any interest whatsoever, in the media.
Yet, in his ‘Introduction to the Revised and Expanded Edition’, Gould doubles down on this line of defence, writing:

“I focused upon the ‘great’ arguments and errors of historical originators, not on transient and ephemeral modern usages. Five years from now, who will remember… our current and largely derivative gladiators; but we can (and must) never forget the brilliance of Darwin and the truly great and informative errors made by his last generation of creationist opponents” (Revised and Extended edition: p23).

Thus, Gould writes:

“I wrote about the great and original arguments, and virtually ignored the modern avatars” (Revised and Extended edition: p23).

Yet this argument makes little sense because, while we may indeed “never forget” the work of Darwin, the same is certainly not true of the nineteenth century pioneers in craniometry and physical anthropology, as well as most of the early twenieth century pioneers in intelligence testing, upon whom Gould focuses most of his invective. On the contrary, most of these figures had already long previously been forgotten by the time Gould wrote his book, and are moreover hardly considered as producing “great and original arguments” on par with those of Darwin, least of all by Gould himself.
At any rate, for all its brilliance, the work of Darwin is also obviously very dated. For example, Darwin had no knowledge of genes or the mechanism of heredity. Yet a critique of Darwin’s theory of natural selection that focussed on this omission would hardly be considered an adequate critique of the modern theory of evolution even by the most rabid of contemporary creationists, since this omission has long previously been rectified by subsequent generations of evolutionary biologists.
As I have written previously:

“One of the hallmarks of true science is the speed at which cutting-edge work becomes obsolete. Religious believers still cite holy books written millennia ago, while adherents of pseudo-sciences like psychoanalysis and Marxism still paw over the words of Freud and Marx. However, the scientific method is a cumulative process based on falsificationism and is moreover no respecter of persons. Scientific works become obsolete almost as fast as they are published. Modern biologists only rarely cite Darwin.”

[4] Even modern scientists working in the fields of psychometrics, biological anthropology and neuroscience would be unlikely to be familiar with such research, since modern scientists are, quite naturally, concerned with the latest state-of-the-art research in their field, not the work of early pioneers that has long previously been built upon and supplanted. As Jensen, himself a leading researcher in the field of intelligence research at the time Gould’s book was authored, put it when reviewing Gould’s book:

“Frankly, I feel little inclination to comb the many archaic references on which most of Gould’s debunking depends, especially because they are no longer of any concern to modern researchers in these fields” (Jensen 1982: p125).

Only a researcher working in the field of the history of science who happened to have studied this particular area of research during the relevant time period might be expected to wade in, but, even then, s/he could hardly be expected to be familiar with much of the methodological minutiae upon which Gould focusses.

[5] Whether Morton did indeed have any preconceived biases regarding the data he collected is itself disputed. Thus, Lewis et al (2011) claim, “It is doubtful that Morton equated cranial capacity and intelligence”, which would suggest that Morton would not have had any motivation, conscious or otherwise, to fudge his findings in the first place. On this view, Moron was primarily interested in studying and measuring human morphological variation, rather than proving the superiority or inferiority of any particular race. Thus, Michael infers:

“He was trying to understand human racial variation, and not, as Gould claims, trying to prove Caucasian racial or intellectual superiority” (Michael 1988: p353).

[6] Thus, Michael himself concludes in 1988 paper by writing:

“Although Gould is mistaken in many of his assumptions and his work, he is correct in asserting that [Morton’s data] is unsound. He fails, however, to mention the overriding reason for rejecting them, namely Morton’s acceptance of the concept of race” (Michael 1988: p353).

Indeed, some fifteen years later, Michael even took to the internet to, among other things, disavow the use that some racialists such as Rushton had been making of his research.

[7] Interestingly, even Gould’s flawed purported reanalysis of Gould’s data fails to eliminate entirely the population differences reported by Morton and others. Thus, even Gould’s “Corrected values for Morton’s Final Tabulation” report the largest cranial capacity for “Mongoloids” and “Modern Caucasians” and the smallest among “Africans” (p66: Table 2.5). (No figures are given in respect of other groups such as Eskimos and Australian Aboriginals. Morton apparently lacked any Eskimo skulls and had very few Australian Aboriginal skulls.) Thus, Gould is reduced merely to asserting that:

“My correction of Morton’s conventional ranking reveals no significant differences among races for Morton’s own data [emphasis added]” (p67).

[8] In writing this review, and searching for the relevant passages to quote in both a hard copy of the 1981 edition and a pdf version of “Revised and Expanded” 1996 edition, I was surprised to discover that, as mentioned above, the whole section of text from which both this quotation and the quotation immediately preceding it were taken (namely, what was, in the original edition, the final section of Gould’s third chapter on “Measuring Heads: Paul Broca and the Heyday of Craniology”, and which has the subheading “Postscript” and runs from p108-112) is omitted from the “Revised and Extended” edition. As a result, there is no systematic treatment of Gould’s position on the relationship between brain size and intelligence among humans in this more recent edition. In his own review of the “Revised and Expanded edition”, Philippe Rushton infers:

“Gould realized that repeating this section verbatim, given the weight of the new evidence, would destroy his entire thesis. Rather than revise his arguments in light of the truth, Gould chose to repeat them without change and to withhold any evidence to the contrary. Both Gould and his publisher owe it to their readers to explain why this supposedly ‘new’ edition studiously avoids any mention of all the new evidence” (Rushton 1997).

[9] The correlation between height and IQ is around r = 0.2, a modest but robust positive correlation. The correlation between external head measurements (e.g. head circumference) is similar, but when brain size is measured directly (e.g. by MRI scans) the correlation is higher, at around r = 0.3, which would be described as a moderate or modest-to-moderate correlation.

[10] Indeed, despite its popularity as a slogan, the very phrase ‘correlation does not imply causation’ itself strikes me as problematic, or at least potentially misleading. It would, in my opinion, be more accurate to say:

‘Correlation does not always necessarily imply a direct causal relationship in and of itself, and moreover of itself implies nothing regarding either the direction of causation nor the nature and directness of the causal nexus.’

Perhaps, however, this is somewhat less catchy and easy to remember and quote and hence less likely to catch on.

[11] Burt is, of course, another researcher whom Gould and others have expended much ink in posthumously defaming when he was safely deceased and hence no longer around to defend himself or his research. Actually, however, although his research has been written up in textbooks as a classic case of scientific fraud, the case against Burt has always struck me as surprisingly weak.
Thus, the first, and, still, to this day, the main evidence cited in support of the contention that Burt was responsible for fabricating his data was the observation of leftist psychologist and political activist Leon Kamin of an odd apparent anomaly in the data collected by Burt regarding the correlation in IQs among identical twins, Thus, according to Gould, Kamin noticed that, in his later publications:

“Burt had increased his sample of twins from fewer than twenty to more than fifty in a series of publications, [but] the average correlation between pairs for IQ remained unchanged to the third decimal place—a statistical situation so unlikely that it matches our vernacular definition of impossible” (p235).

Actually, Gould’s phraseology here in sloppy and statistically imprecise. It was not the “average correlation between pairs for IQ” that remained unchanged, but the correlation coefficient between the IQ scores of identical twins.
Yet the idea that this statistical anomaly was indeed necessarily anomalous, let alone decisive proof of fabrication, seems to me to rest on an elementary statistical error.
Thus, it is indeed true, as alleged by Gould and Kamin, that it is very unlikely that correlation coefficient would have remained unchanged to three decimal places despite an increase in sample size “from fewer than twenty to more than fifty”.
However, it is no less unlikely that the average correlation would have changed by, say, exactly 0.003, or precisely 0.014.
In short, after increasing your sample size by more than 150%, any specific average correlation that you might predict beforehand would equally unlikely. An average correlation exactly the same as that found prior to increasing your sample size is, in principle, no more improbable than a correlation, say, exactly 0.002 higher, or 0.002 lower than that found formerly.
(It must also, of course, be borne in mind that one would expect the correlation to be very similar, since other studies of identical twins have also reported a very similar correlation coefficient, and moreover Burt’s later samples were appaently only expansions of his earlier samples and therefore the data overlapped.)
Indeed, given the amount of scientific research that is conducted each year, statistically unlikely results are statistically very likely to occur quite often.
Indeed, one might even argue that the identical correlation coefficients reported by Burt actually argue against deliberate fabrication, since, if Burt were indeed fabricating his findings, he would surely never have reported such an apparently suspicious result.
Interestingly, Burt is among the few intelligence researchers whom Gould does not accuse of racism. After all, Burt lived and worked in Britain in the early twentieth century, a time when the population of Britain was almost exclusively white. Indeed, he spent a large part of his career working for London County Council in a London that was, in stark contrast to the London of today, overwhelmingly white. As a result, neither he nor his employer evinced much interest in racial disparities in achievement.
Yet, rather than accusing Burt of racial prejudice, Gould instead accuses him of class prejudice, and blames Burt for his role in the introduction of the 11+ examination system in the UK, whereby pupils were allocated to different types of school, emphasising different forms of education, based on their performance in standardized tests at age 11, whose “major effect… in terms of human lives and hopes, surely lay with its primary numerical result—80 percent branded as unfit for higher education by reason of low innate intellectual ability” (p295).
He is dismissive of Burt’s claim that “his primary goal in supporting 11+ was… to provide access to higher education for disadvantaged children whose innate talents might otherwise not be recognized”, since, according to Gould, “Burt himself did not believe that many people of high intelligence lay hidden in the lower classes” (p295).
Burt did indeed argue that intellectually gifted children were relatively less frequently to be found among poor families than among the families of the wealthy and eminent. This is indeed inevitable, as Burt himself observed, and Richard Herrnstein was later to famously reiterate, if one accepts both that intellectual ability is associated with upward social mobility, and that intellectual ability is passed down in families, whether biologically or indeed culturally.
However, from this, it does not follow, as Gould asserts, that Burt therefore “did not believe that many people of high intelligence lay hidden in the lower classes” (p295).
On the contrary, although there may be a lesser relative proportion of gifted children among the working classes than among the upper- and middle-classes, there could still be a great number in absolute terms, especially since, at this time, working class people constituted the great majority of the population of the UK. Indeed given the greater numbers of working classes people, gifted children from the working-classes could even have outnumbered those from among the upper- and upper-middle classes.
As for the 11+ examination system (introduced, incidentally, by perhaps the most radical and reforming left-wing government in British history), this system surely not uncoincidentally coincided with higher proportions of children from working-class backgrounds ascending to professional occupations than has been observed either before the system’s introduction or after its abolition.

[12] Along with his rejection of the g factor, Gould explicitly champions Gardner’s theory of multiple intelligences, approvingly citing Gardner’s critique of the g factor and, in his ‘Introduction to the Revised and Expanded Edition’ crediting the latter’s the “theory of multiple intelligences [as] the major challenge to Jensen in the last generation, to Herrnstein and Murray today, and to the entire tradition of rankable, unitary intelligence marking the mismeasure of man” (Revised and Extended edition: p22).

[13] Indeed, to some extent, this is indeed true. Thus, although most variation in intelligence, as between groups no less than as between individuals, is captured by the g factor, nevertheless some races do indeed score relatively higher in certain specific abilities, for example, East Asians in spatial-visual and mathematical ability; Ashkenazi Jews in verbal ability; blacks in rote memory; and Australian Aboriginals in spatial memory. However, most variation in intelligence, including that between groups, is captured by the g factor. In other words, groups that score higher in one form of intelligence generally also score higher in other forms of intelligence too. Groups, no less than individuals, differ in g.

[14] We can illustrate this point by looking at physiological differences between groups. Thus, it is perfectly possible that two races might have evolved to be exactly equal in one specific physiological measure. For example, the reported average heights for black and white American adult males is virtually identical. Despite their very different evolutionary histories, black and white males resident in America seem then to be almost exactly equal for this trait.
However, the same is obviously not true of other racial groups resident in the USA, for example, East Asians, South Asians or Hispanics, most of whom are considerably shorter on average than either white or black Americans. Moreover, even blacks and whites differ in respect of other bodily measures and dimensions, even those other bodily measurements that correlate with height.
Thus, to take one example I have discussed earlier in this piece, black American men, despite being of the same average height as white males, have smaller head and brain size, on average. They also have somewhat longer legs, on average, than white Americans. This is despite the fact that both these measures (brain size and leg length) are themselves positively correlated with height, whereas the different forms of intelligence posited by Gardner and Sternberg were originally conceived as being largely, if not wholly, independent of one another (though Gardner, faced with the overwhelming evidence in favour of a g factor, later revised this view).
In short, the more different measures employed, and the more different racial groups in respect of whom the measurements are conducted, the less likely it is that every single group will be exactly equal in respect of every single one of the measurements. Moreover, this is especially unlikely to be the case where the measurements in question are uncorrelated with one another, as was alleged to be the case in respect of the multiple intelligences posited by Gardner and Sternberg.

___________________________

References

Jensen (1982). The Debunking of Scientific Fossils and Straw Persons Contemporary Education Review. 1(2):121–35.

Jensen & Johnson (1994) Race and sex differences in head size and IQ, Intelligence 18(3): 309-333

Kim & von dem Knesebeck (2018) Income and obesity: what is the direction of the relationship? A systematic review and meta-analysis BMJ Open 8(1):e019862

Kirolos et al (2022) Neurodevelopmental, cognitive, behavioural and mental health impairments following childhood malnutrition: a systematic review BMJ Global Health 7(7): e009330

Lee et al (2019) The causal influence of brain size on human intelligence: Evidence from within-family phenotypic associations and GWAS modeling, Intelligence 75: 48-58.

Lewis et al (2011) The Mismeasure of Science: Stephen Jay Gould versus Samuel George Morton on Skulls and Bias. PLoS Biol 9(6): e1001071.

Michael (1988) A new look at Morton’s craniological research 29(2):349-354.

Pietschnig et al (2015) Meta-analysis of associations between human brain volume and intelligence differences: How strong are they and what do they mean? Neuroscience & Biobehavioral Reviews 57: 411-432.

Soliman et al (2021) Early and Long-term Consequences of Nutritional Stunting: From Childhood to Adulthood Acta bio-medica: Atenei Parmensis 92(1):2021168

Rushton (1996) Race, intelligence and the brain: The errors and omissions of the ‘revised’ edition of S. J. Gould’s ‘The Mismeasure of Man’ (1996), Personality & Individual Differences, 23(1): 169-180.

Rushton & Ankney (2009) Whole Brain Size and General Mental Ability: A Review. International Journal of Neuroscience, 119(5):692-732.

Zhou (2021) The shifting income-obesity relationship: Conditioning effects from economic development and globalization SSM – Population Health 15: 100849

‘The Bell Curve’: A Book Much Read About, But Rarely Actually Read

‘The Bell Curve: Intelligence and Class Structure in American Life’ by Richard Herrnstein and Charles Murray (New York: Free Press, 1994). 

There’s no such thing as bad publicity’ – or so contends a famous adage of the marketing industry. 

‘The Bell Curve: Intelligence and Class Structure in America’ by Richard Herrnstein and Charles Murray is perhaps a case in point. 

This dry, technical, academic social science treatise, full of statistical analyses, graphs, tables, endnotes and appendices, and totalling almost 900 pages, became an unlikely nonfiction bestseller in the mid-1990s on a wave of almost universally bad publicity in which the work was variously denounced as racist, pseudoscientific, fascist, social Darwinist, eugenicist and sometimes even just plain wrong. 

Readers who hurried to the local bookstore eagerly anticipating an incendiary racialist polemic were, however, in for a disappointment. 

Indeed, one suspects that, along with ‘The Bible’ and Stephen Hawkins’ ‘A Brief History of Time’, ‘The Bell Curve’ became one of those bestsellers that many people bought, but few managed to finish. 

‘The Bell Curve’ thus became, like another book that I have recently reviewed, a book much read about, but rarely actually read – at least in full. 

As a result, as with that other book, many myths have emerged regarded the content of ‘The Bell Curve’ that are quite contradicted when one actually takes the time and trouble to read it for oneself. 

Subject Matter 

The first myth of ‘The Bell Curve’ is that it was a book about race differences, or, more specifically, about race differences in intelligence. In fact, however, this is not true. 

Thus, ‘The Bell Curve’ is a book so controversial that the controversy begins with the very identification of its subject-matter. 

On the one hand, the book’s critics focused almost exclusively on subject of race. This led to the common perception that ‘The Bell Curve’ was book about race and race differences in intelligence.[1]

Ironically, many racialists seem to have taken these leftist critics at their word, enthusiastically citing the work as support for their own views regarding race differences in intelligence.  

On the other hand, however, surviving co-author Charles Murray insisted from the outset that the issue of race, and of race differences in intelligence, was always peripheral to he and co-author Richard Herrnstein’s primary interest and focus, which was, he claimed, on the supposed emergence of a ‘Cognitive Elite’ in modern America. 

Actually, however, both these views seem to be incorrect. While the first section of the book does indeed focus on the supposed emergence of a ‘Cognitive Elite’ in modern America, the overall theme of the book seems to be rather broader. 

Thus, the second section of the book focuses on the association between intelligence and various perceived social pathologies, such as unemployment, welfare dependency, illegitimacy, crime and single-parenthood. 

To the extent the book has a single overarching theme, one might say that it is a book about the social and economic correlates of intelligence, as measured by IQ tests, in modern America.  

Its overall conclusion is that intelligence is indeed a strong predictor of social and economic outcomes for modern Americans – high intelligence with socially desirable outcomes and low intelligence with socially undesirable ones. 

On the other hand, however, the topic of race is not quite as peripheral to the book’s themes as sometimes implied by Murray and some of his defenders. 

Thus, it is sometimes claimed only a single chapter dealt with race. Actually, however, two chapters focus on race differences, namely chapters 13 and 14, respectively titled ‘Ethnic Differences in Cognitive Ability’ and ‘Ethnic Inequalities in Relation to IQ’. 

In addition, a further two chapters, namely chapters 19 and 20, entitled respectively ‘Affirmative Action in Higher Education’ and ‘Affirmative Action in the Workplace’, deal with the topic of affirmative action, as does the final appendix, entitled ‘The Evolution of Affirmative Action in the Workplace’ – and, although affirmative action has been employed to favour women as well as racial minorities, it is with racial preferences that Herrnstein and Murray are primarily concerned. 

However, these chapters represent only 142 of the book’s nearly 900 pages. 

Moreover, in much of the remainder of the book, the authors actually explicitly restrict their analysis to white Americans exclusively. They do so precisely because the well documented differences between the races in IQ as well as in many of the social outcomes whose correlation with IQ the book discusses would mean that race would have represented a potential confounding factor that they would otherwise have to take steps to control for. 

Herrnstein and Murray therefore took to decision to extend their analysis to race differences near the end of their book, in order to address the question of the extent to which differences in intelligence, which they have already demonstrated to be an important correlate of social and economic outcomes among whites, are also capable of explaining differences in achievement as between races. 

Without these chapters, the book would have been incomplete, and the authors would have laid themselves open to the charge of political-correctness and of ignoring the ‘elephant in the room’. 

Race and Intelligence 

If the first controversy of ‘The Bell Curve’ concerns whether it is a book primarily book about race and race differences in intelligence, the second controversy is over what exactly the authors concluded with respect to this vexed and contentious issue. 

Thus, the same leftist critics who claimed that ‘The Bell Curve’ was primarily a book about race and race differences in intelligence, also accused the authors of concluding that black people are innately less intelligent than whites. 

Some racists, as I have already noted, evidently took the leftists at their word, and enthusiastically cite the book as support and authority for this view. 

However, in subsequent interviews, Murray always insisted he and Herrnstein had actually remained “resolutely agnostic” on the extent to which genetic factors underlay the IQ gap. 

In the text itself, Herrnstein and Murray do indeed declare themselves “resolutely agnostic” with regard to the extent of the genetic contribution to the test score gap (p311).

However, just couple of sentences before they use this very phrase, they also appear to conclude that genes are indeed at least part of the explanation, writing: 

“It seems highly likely to us that both genes and the environment have something to do with racial differences [in IQ]” (p311). 

This paragraph, buried near the end of chapter 13, during an extended discussion of evidence relating to the causes of race differences in intelligence, is the closest the authors come to actually declaring any definitive conclusion regarding the causes of the black-white test score gap.[2]

This conclusion, though phrased in sober and restrained terms, is, of course, itself sufficient to place its authors outside the bounds of acceptable opinion in the early-twenty-first century, or indeed in the late-twentieth century when the book was first published, and is sufficient to explain, and, for some, justify, the opprobrium heaped upon the book’s surviving co-author from that day forth. 

Intelligence and Social Class

It seems likely that races which evolved on separate continents, in sufficient reproductive isolation from one another to have evolved the obvious (and not so obvious) physiological differences between races that we all observe when we look at the faces, or bodily statures, of people of different races (and that we indirectly observe when we look at the results of different athletic events at the Olympic Games), would also have evolved to differ in psychological traits, including intelligence. 

Indeed, it is surely unlikely, on a priori grounds alone, that all different human races have evolved, purely by chance, the exact same level of intelligence. 

However, if races differ in intelligence are therefore probable, the case for differences in intelligence as between social classes is positively compelling. 

Indeed, on a priori grounds alone, it is inevitable that social classes will come to differ in IQ, if one accepts two premises, namely: 

1) Increased intelligence is associated with upward social mobility; and 
2) Intelligence is passed down in families.

In other words, if more intelligent people tend, on average, to get higher-paying jobs than those of lower intelligence, and the intelligence of parents is passed on to their offspring, then it is inevitable that the offspring of people with higher-paying jobs will, on average, themselves be of higher intelligence than are the offspring of people with lower paying jobs.  

This, of course, follows naturally from the infamous syllogism formulated by ‘Bell Curve’ co-author Richard Herrnstein way back in the 1970s (p10; p105). 

Incidentally, this second premise, namely that intelligence is passed down in families, does not depend on the heritability of IQ in the strict biological sense. After all, even if heritability of intelligence were zero, intelligence could still be passed down in families by environmental factors (e.g. the ‘better’ parenting techniques of high IQ parents, or the superior material conditions in wealthy homes). 

The existence of an association between social class and IQ ought, then, to be entirely uncontroversial to anyone who takes any time whatsoever to think about the issue. 

If there remains any room for reasoned disagreement, it is only over the direction of causation – namely the question of whether:  

1) High intelligence causes upward social mobility; or 
2) A privileged upbringing causes higher intelligence.

These two processes are, of course, not mutually exclusive. Indeed, it would seem intuitively probable that both factors would be at work. 

Interestingly, however, evidence demonstrates the occurrence only of the former. 

Thus, even among siblings from the same family, the sibling with the higher childhood IQ will, on average, achieve higher socioeconomic status as an adult. Likewise, the socioeconomic status a person achieves as an adult correlates more strongly with their own IQ score than it does with the socioeconomic status of their parents or of the household they grew up in (see Straight Talk About Mental Tests: p195). 

In contrast, family, twin and adoption studies and of the sort conducted by behavioural geneticists have concurred in suggesting that the so-called shared family environment (i.e. those aspects of the family environment shared by siblings from the same household, including social class) has but little effect on adult IQ. 

In other words, children raised in the same home, whether full- or half-siblings or adoptees, are, by the time they reach adulthood, no more similar to one another in IQ than are children of the same degree of biological relatedness brought up in entirely different family homes (see The Nurture Assumption: reviewed here). 

However, while the direction of causation may still be disputed by intelligent (if uninformed) laypeople, the existence of an association between intelligence and social class ought not, one might think, be in dispute. 

However, in Britain today, in discussions of social mobility, if children from deprived backgrounds are underrepresented, say, at elite universities, then this is almost invariably taken as incontrovertible proof that the system is rigged against them. The fact that children from different socio-economic backgrounds differ in intelligence is almost invariably ignored. 

When mention is made of this incontrovertible fact, leftist hysteria typically ensues. Thus, in 2008, psychiatrist Bruce Charlton rightly observed that, in discussion of social mobility: 

“A simple fact has been missed: higher social classes have a significantly higher average IQ than lower social classes” (Clark 2008). 

For his trouble, Charlton found himself condemned by the National Union of Students and assorted rent-a-quote academics and professional damned fools, while even the ostensibly ‘right-wing’ Daily Mail newspaper saw fit to publish a headline “Higher social classes have significantly HIGHER IQs than working class, claims academic”, as if this were in some way a controversial or contentious claim (Clark 2008). 

Meanwhile, when, in the same year, a professor at University College a similar point with regard the admission of working-class students to medical schools, even the then government Health Minister, Ben Bradshaw, saw fit to offer his two cents worth (which were not worth even that), declaring: 

“It is extraordinary to equate intellectual ability with social class” (Beckford 2008). 

Actually, however, what is truly extraordinary is that any intelligent person, least of all a government minister, would dispute the existence of such a link. 

Cognitive Stratification 

Herrnstein’s syllogism leads to a related paradox – namely that, as environmental conditions are equalized, heritability increases. 

Thus, as large differences in the sorts of environmental factors known to affect IQ (e.g. malnutrition) are eliminated, so differences in income have come to increasingly reflect differences in innate ability. 

Moreover, the more gifted children from deprived backgrounds who escape their humble origins, then, given the substantial heritability of IQ, the fewer such children will remain among the working-class in subsequent generations. 

The result is what Herrnstein and Murray call the ‘Cognitive Stratification’ of society and the emergence of what they call a ‘Cognitive Elite’. 

Thus, in feudal society, a man’s social status was determined largely by ‘accident of birth’ (i.e. he inherited the social station of his father). 

Women’s status, meanwhile, was determined, in addition, by what we might call ‘accident of marriage’ – and, to a large extent, it still is. 

However, today, a person’s social status, at least according to Herrnstein and Murray, is determined primarily, and increasingly, by their level of intelligence. 

Of course, people are not allocated to a particular social class by IQ testing itself. Indeed, the use of IQ tests by employers and educators has been largely outlawed on account of its ‘disparate impact‘ (or ‘indirect discrimination’, to use the equivalent British phrase) with regard to race (see below). 

However, the skills and abilities increasingly valued at a premium in western society (and, increasingly, many non-western societies as well), mean that, through the operation of the education system and labour market, individuals are effectively sorted by IQ, even without anyone ever actually sitting an IQ test. 

In other words, society is becoming increasingly meritocratic – and the form of ostensible ‘merit’ upon which attainment is based is intelligence. 

For Herrnstein and Murray, this is a mixed blessing: 

“That the brightest are identified has its benefits. That they become so isolated and inbred has its costs” (p25). 

However, the correlation between socioeconomic status and intelligence remains imperfect. 

For one thing, there are still a few highly remunerated, and very high-status, occupations that rely on skills that are not especially, if at all, related to intelligence.  I think here, in particular, of professional sports and the entertainment industry. Thus, leadings actors, pop stars and sports stars are sometimes extremely well-remunerated, and very high-status, but may not be especially intelligent.  

More importantly, while highly intelligent people might be, by very definition, the only ones capable of performing cognitively-demanding, and hence highly remunerated, occupations, this is not to say all highly intelligent people are necessarily employed in such occupations. 

Thus, whereas all people employed in cognitively-demanding occupations are, almost by definition, of high intelligence, people of all intelligence levels are capable of doing cognitively-undemanding jobs.

Thus, a few people of high intellectual ability remain in low-paid work, whether on account of personality factors (e.g. laziness), mental illness, lack of opportunity or sometimes even by choice (which choice is, of course, itself a reflection of personality factors). 

Therefore, the correlation between IQ and occupation is far from perfect. 

Job Performance

The sorting of people with respect to their intelligence begins in the education system. However, it continues in the workplace. 

Thus, general intelligence, as measured by IQ testing, is, the authors claim, the strongest predictor of occupational performance in virtually every occupation. Moreover, in general, the higher paid and higher status the occupation in question, the stronger the correlation between performance and IQ. 

However, Herrnstein and Murray are at pains to emphasize, intelligence is a strong predictor of occupational performance even in apparently cognitively undemanding occupations, and indeed almost always a better predictor of performance than tests of the specific abilities the job involves on a daily basis. 

However, in the USA, employers are barred from using testing to select among candidates for a job or for promotion unless they can show the test has ‘manifest relationship’ to the work, and the burden of proof is on the employer to show such a relationship. Otherwise, given their ‘disparate impact’ with regard to race (i.e. the fact that some groups perform worse), the tests in question are deemed indirectly discriminatory and hence unlawful. 

Therefore, employers are compelled to test, not general ability, but rather the specific skills required in the job in question, where a ‘manifest relationship’ is easier to demonstrate in court. 

However, since even tests of specific abilities almost invariably still tap into the general factor of intelligence, races inevitably score differently even on these tests. 

Indeed, because of the ubiquity and predictive power of the g factor, it is almost impossible to design any type of standardized test, whether of specific or general ability or knowledge, in which different racial groups do not perform differently. 

However, if some groups outperform others, the American legal system presumes a priori that this reflects test bias rather than differences in ability. 

Therefore, although the words “all men are created equal” are not, contrary to popular opinion, part of the US constitution, the Supreme Court has effectively decided, by legal fiat, to decide cases as if they were. 

However, just as a law passed by Congress cannot repeal the law of gravity, so a legal presumption that groups are equal in ability cannot make it so. 

Thus, the bar on the use of IQ testing by employers has not prevented society in general from being increasingly stratified by intelligence, the precise thing measured by the outlawed tests. 

Nevertheless, Herrnstein and Murray estimate that the effective bar on the use of IQ testing makes this process less efficient, and cost the economy somewhere between 80 billion to 13 billion dollars in 1980 alone (p85). 

Conscientiousness and Career Success

I am skeptical of Herrnstein and Murray’s conclusion that IQ is the best predictor of academic and career success. I suspect hard work, not to mention a willingness to toady, toe the line, and obey orders, is at least as important in even the most cognitively-demanding careers, as well as in schoolwork and academic advancement. 

Perhaps the reason these factors have not (yet) been found to be as highly correlated with earnings as is IQ is that we have not yet developed a way of measuring these aspects of personality as accurately as we can measure a person’s intelligence through an IQ test. 

For example, the closest psychometricians have come to measuring capacity for hard work is the personality factor known as ‘conscientiousness’, one of the Big Five factors of personality revealed by psychometric testing. 

Conscientiousness does indeed correlate with success in education and work (e.g. Barrick & Mount 1991). However, the correlation is weaker than that between IQ and success in education and at work. 

However, this may be because personality is less easily measured by current psychometric methods than is intelligence – not least because personality tests generally rely on self-report, rather than measuring actual behaviour. 

Thus, to assess conscientiousness, questionnaires ask respondents whether they ‘see themselves as organized’, ‘as able to follow an objective through to completion’, ‘as a reliable worker’, etc. 

This would be the equivalent of an IQ test that, instead of directly testing a person’s ability to recognize patterns or manipulate shapes by having them do just this, simply asked respondents how good they perceived themselves as being at recognizing patterns, or manipulating shapes. 

Obviously, this would be a less accurate measure of intelligence than a normal IQ test. After all, some people lie, some are falsely modest and some are genuinely deluded. 

Indeed, according to the Dunning Kruger effect, it is those most lacking in ability who most overestimate their abilities – precisely because they lack the ability to accurately assess their ability (Kruger & Dunning 1999). 

In an IQ test, on the other hand, one can sometimes pretend to be dumber than one is, by deliberately getting questions wrong that one knows the answer to.[3]

However, it is not usually possible to pretend to be smarter than one is by getting more questions right simply because one would not know what are the right answers. 

‘Affirmative Action’ and Test Bias 

In chapters nineteen and twenty, respectively entitled ‘Affirmative Action in Higher Education’ and ‘Affirmative Action in the Workplace’, the authors discuss so-called ‘affirmative action’, an American euphemism for systematic and overt discrimination against white males. 

It is well-documented that, in the United States, blacks, on average, earn less than white Americans. On the other hand, it is less well-documented that whites, on average, earn less than people of Indian, Chinese and Jewish ancestry. 

With the possible exception of Indian-Americans, these differences, of course, broadly mirror those in average IQ scores. 

Indeed, according to Herrnstein and Murray, the difference in earnings between whites and blacks, not only disappears after controlling for differences in IQ, but is actually partially reversed. Thus, blacks are actually somewhat overrepresented in professional and white-collar occupations as compared to whites of equivalent IQ. 

This remarkable finding Herrnstein and Murray attribute to the effects of affirmative action programmes, as black Americans are appointed and promoted beyond what their ability merits because through discrimination. 

Interestingly, however, this contradicts what the authors wrote in an earlier chapter, where they addressed the question of test bias (pp280-286). 

There, they concluded that testing was not biased against African-Americans, because, among other reasons, IQ tests were equally predictive of real-world outcomes (e.g. in education and employment) for both blacks and whites, and blacks do not perform any better in the workplace or in education than their IQ scores predict. 

This is, one might argue, not wholly convincing evidence that IQ tests are not biased against blacks. It might simply suggest that society at large, including the education system and the workplace, is just as biased against blacks as are the hated IQ tests. This is, of course, precisely what we are often told by the television, media and political commentators who insist that America is a racist society, in which such mysterious forces as ‘systemic racism’ and ‘white privilege’ are pervasive. 

In fact, the authors acknowledge this objection, conceding:  

“The tests may be biased against disadvantaged groups, but the traces of bias are invisible because the bias permeates all areas of the group’s performance. Accordingly, it would be as useless to look for evidence of test bias as it would be for Einstein’s imaginary person traveling near the speed of light to try to determine whether time has slowed. Einstein’s traveler has no clock that exists independent of his space-time context. In assessing test bias, we would have no test or criterion measure that exists independent of this culture and its history. This form of bias would pervade everything” (p285). 

Herrnstein and Murray ultimately reject this conclusion on the grounds that it is simply implausible to assume that: 

“[So] many of the performance yardsticks in the society at large are not only biased, they are all so similar in the degree to which they distort the truth-in every occupation, every type of educational institution, every achievement measure, every performance measure-that no differential distortion is picked up by the data” (p285). 

In fact, however, Nicholas Mackintosh identifies one area where IQ tests do indeed under-predict black performance, namely with regard to so-called adaptive behaviours – i.e. the ability to cope with day-to-day life (e.g. feed, dress, clean, interact with others in a ‘normal’ manner). 

Blacks with low IQs are generally much more functional in these respects than whites or Asians with equivalent low IQs (see IQ and Human Intelligence: p356-7).[4]

Yet Herrnstein and Murray seem to have inadvertently, and evidently without realizing it, identified yet another sphere where standardized testing does indeed under-predict real-world outcomes for blacks. 

Thus, if indeed, as Herrnstein and Murray claim, blacks are somewhat overrepresented among professional and white-collar occupations relative to their IQs, this suggests that blacks do indeed do better in real-world outcomes than their test results would predict and, while Herrnstein and Murray attribute this to the effect of discrimination against whites, it could instead surely be interpreted as evidence that the tests are biased against blacks. 

Policy Implications? 

What, then, are the policy implications that Herrnstein and Murray draw from the findings that they report? 

In The Blank Slate: The Modern Denial of Human Nature, cognitive science, linguist and popular science writer Steven Pinker popularizes the notion that recognizing the existence of innate differences between individuals and groups in traits such as intelligence does not necessarily lead to ‘right-wing’ political implications. 

Thus, a leftist might accept the existence of innate differences in ability, but conclude that, far from justifying inequality, this is all the more reason to compensate the, if you like, ‘cognitively disadvantaged’ for their innate deficiencies, differences which are, being innate, hardly something for which they can legitimately be blamed. 

Herrnstein and Murray reject this conclusion, but acknowledge it is compatible with their data. Thus, in an afterword to later editions, Murray writes: 

“If intelligence plays an important role in determining how well one does in life, and intelligence is conferred on a person through a combination of genetic and environmental factors over which that person has no control, the most obvious political implication is that we need a Rawlsian egalitarian state, compensating the less advantaged for the unfair allocation of intellectual gifts” (p554).[5]

Interestingly, Pinker’s notion of a ‘hereditarian left’, and the related concept of ‘Bell Curve liberals’, is not entirely imaginary. On the contrary, it used to be quite mainstream. 

Thus, it was the radical leftist post-war Labour government that imposed the tripartite system on schools in the UK in 1945, which involved allocating pupils to different schools on the basis of their performance in what was then called the 11-plus exam, conducted at with children at age eleven, which tested both ability and acquired knowledge. This was thought by leftists to be a fair system that would enable bright, able youngsters from deprived and disadvantaged working-class backgrounds to achieve their full potential.[6]

Indeed, while contemporary ‘Cultural Marxists’ emphatically deny the existence of innate differences in ability as between individuals and groups, Marx himself, laboured under no such delusion. 

On the contrary, in advocating, in his famous (plagiarized) aphorism “From each according to his ability; to each according to his need”, Marx implicitly recognized that individuals differ in “ability”, and, given that, in the unrealistic communist utopia he envisaged, environmental conditions were ostensibly to be equalized, these differences he presumably conceived of as innate in origin. 

However, a distinction must be made here. While it is possible to justify economic redistributive policies on Rawlsian grounds, it is not possible to justify affirmative action. 

Thus, one might well reasonably contend that the ‘cognitively disadvantaged’ should be compensated for their innate deficiencies through economic redistribution. Indeed, to some extent, most Western polities already do this, by providing welfare payments and state-funded, or state-subsidized, care to those whose cognitive impairment is such as to qualify as a disability and hence render them incapable of looking after or providing for themselves. 

However, we are unlikely to believe that such persons should be given entry to medical school such that they are one day liable to be responsible for performing heart surgery on us or diagnosing our medical conditions. 

In short, socialist redistribution is defensible – but affirmative action is definitely not! 

Reception and Readability 

The reception accorded ‘The Bell Curve’ in 1994 echoed that accorded another book that I have also recently reviewed, but that was published some two decades earlier, namely Edward O. Wilson’s Sociobiology: The New Synthesis. 

Both were greeted with similar indignant moralistic outrage by many social scientists, who even employed similar pejorative soundbites (‘genetic determinism’, ‘reductionism’, ‘biology as destiny’), in condemning the two books. Moreover, in both cases, the academic uproar even spilled over into a mainstream media ‘moral panic’, with pieces appearing the popular press attacking the two books. 

Yet, in both cases, the controversy focused almost exclusively on just a small part of each book – the single chapter in ‘Sociobiology: The New Synthesis’ focusing on humans and the few chapters in ‘The Bell Curve’ discussing race. 

In truth, however, both books were massive tomes of which these sections represented only a small part. 

Indeed, due to their size, one suspects most critics never actually read the books in full for themselves, including, it seemed, most of those nevertheless taking it upon themselves to write critiques. This is what led to the massive disconnect between what most people thought the books said, and their actual content. 

However, there is a crucial difference. 

‘Sociobiology: The New Synthesis’ was a long book of necessity, given the scale of the project Wilson set himself. 

As I have written in my review of that latter work, the scale of Wilson’s ambition can hardly be exaggerated. He sought to provide a new foundation for the whole field of animal behaviour, then, almost as an afterthought, sought to extend this ‘New Synthesis’ to human behaviour as well, which meant providing a new foundation, not for a single subfield within biology, but for several whole disciplines (psychology, sociology, economics and cultural anthropology) that were formerly almost unconnected to biology. Then, in a few provocative sentences, he even sought to provide a new foundation for moral philosophy, and perhaps epistemology too. 

‘Sociobiology: The New Synthesis’ was, then, inevitably and of necessity, a long book. Indeed, given that his musings regarding the human species were largely (but not wholly) restricted to a single chapter, one could even make a case that it was too short – and it is no accident that Wilson subsequently extended his writings with regard to the human species to a book length manuscript. 

Yet, while Sociobiology was of necessity a long book, ‘The Bell Curve: Intelligence and Class Structure in America’ is, for me, unnecessarily overlong. 

After all, Herrnstein and Murray’s thesis was actually quite simple – namely that cognitive ability, as captured by IQ testing, is a major correlate of many important social outcomes in modern America. 

Yet they reiterate this point, for different social outcomes, again and again, chapter after chapter, repeatedly. 

In my view, Herrnstein and Murray’s conclusion would have been more effectively transmitted to the audience they presumably sought to reach had they been more succinct in their writing style and presentation of their data. 

Had that been the case then perhaps rather more of the many people who bought the book, and helped make it into an unlikely nonfiction bestseller in 1994, might actually have managed to read it – and perhaps even been persuaded by its thesis. 

For casual readers interested in this topic, I would recommend instead Intelligence, Race, And Genetics: Conversations With Arthur R. Jensen (which I have reviewed here, here and here). 

Endnotes

[1] For example, Francis Wheen, a professional damned fool and columnist for the Guardian newspaper (which two occupations seem to be largely interchangeable) claimed that: 

“The Bell Curve (1994), runs to more than 800 pages but can be summarised in a few sentences. Black people are more stupid than white people: always have been, always will be. This is why they have less economic and social success. Since the fault lies in their genes, they are doomed to be at the bottom of the heap now and forever” (Wheen 2000). 

In making this claim, Wheen clearly demonstrates that he has read few if any of those 800 pages to which he refers.

[2] Although their discussion of the evidence relating to the causes, genetic or environmental, of the black-white test score gap is extensive, it is not exhaustive. For example, Phillipe Rushton, the author of Race Evolution and Behavior (reviewed here and here) argues that, despite the controversy their book provoked, Herrnstein and Murray actually “didn’t go far enough on race”, omitting, for example, any real discussion, save a passing mention in Appendix 5, of race differences in brain size (Rushton 1997). On the other hand, Herrnstein and Murray also did not mention studies that failed to establish any correlation between IQ and blood groups among African-Americans, studies interpreted as supporting an environmentalist interpretation of race differences in intelligence (Loehlin et al 1973; Scarr et al 1977). For readers interested in a more complete discussion of the evidence regarding the relative contributions of environment and heredity to the differences in IQ scores of different races, see my review of Richard Lynn’s Race Differences in Intelligence: An Evolutionary Analysis, available here.

[3] For example, some of those accused of serious crimes have been accused of deliberately getting questions wrong on IQ tests in order to qualify as mentally subnormal when before the courts for sentencing in order to be granted mitigation of sentence on this ground, or, more specifically, in order to evade the death penalty. 

[4] This may be because whites or Asians with such low IQs are more likely to have such impaired cognitive abilities because of underlying conditions (e.g chromosomal abnormalities, brain damage) that handicap them over and above the deficit reflected in IQ score alone. On the other hand, blacks with similarly low IQs are still within the normal range for their own race. Therefore, rather than suffering from, say, a chromosomal abnormality or brain damage, they are relatively more likely to simply be at the tail-end of the normal range of IQs within their group, and hence normal in other respects.

[5] The term Rawlsian is a reference to political theorist John Rawles version of social contract theory, whereby he poses the hypothetical question as to what arrangement of political, social and economic affairs humans would favour if placed in what he called ‘the original position’, where they would be unaware of, not only their own race, sex and position in to the socio-economic hierarchy, but also, most important for our purposes, their own level of innate ability. This Rawles referred to as ‘veil of ignorance’.

[6] The tripartite system did indeed enable many working-class children to achieve a much higher economic status than their parents, although this was partly due to the expansion of the middle-class sector of the economy over the same time-period. It was also later Labour administrations who largely abolished the 11-plus system, not least because, unsurprisingly given the heritability of intelligence and personality, children from middle-class backgrounds tended to do better on it than did children from working-class backgrounds.

References 

Barrick & Mount 1991 The big five personality dimensions and job performance: a meta-analysis. Personnel Psychology 44(1):1–26 
Beckford (2008) Working classes ‘lack intelligence to be doctors’, claims academic, Daily Telegraph, 04 Jun 2008. 
Clark 2008 Higher social classes have significantly HIGHER IQs than working class, claims academic Daily Mail, 22 May 2008. 
Kruger & Dunning (1999) Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lead to Inflated Self-Assessments. Journal of Personality and Social Psychology 77(6):1121-34 
Loehlin et al (1973) Blood group genes and negro-white ability differences. Behavior Genetics 3(3): 263-270  
Rushton, J. P. (1997). Why The Bell Curve didn’t go far enough on race. In E. White (Ed.), Intelligence, political inequality, and public policy (pp. 119-140). Westport, CT: Praeger. 
Scarr et al (1977) Absence of a relationship between degree of white ancestry and intellectual skills within a black population. Human Genetics 39(1):69-86 . 
Wheen (2000) The ‘science’ behind racism. Guardian, 10 May 2000. 

Judith Harris’s ‘The Nurture Assumption’: By Parent or Peers

Judith Harris, The Nurture Assumption: Why Children Turn Out the Way They Do. Free Press, 1998.

Almost all psychological traits on which individual humans differ, from personality and intelligence to mental illness, are now known to be substantially heritable. In other words, individual differences in these traits are, at least in part, a consequence of genetic differences between individuals.

This finding is so robust that it has even been termed by Eric Turkenheimer the ‘First Law of Behviour Genetics’ and, although once anathema to most psychologists save a marginal fringe of behavioural geneticists, it has now, under the sheer weight of evidence produced by the latter, belatedly become the new orthodoxy. 

On reflection, however, this transformation is not entirely a revelation. 

After all, it was only in the mid-twentieth century that the curious notion that individual differences were entirely the product of environmental differences first arose, and, even then, this delusion was largely restricted to psychologists, sociologists, feminists and other such ‘professional damned fools’, along with those among the semi-educated public who seek to cultivate an air of intellectualism by aping the former’s affections. 

Before then, poets, peasants and laypeople alike had long recognized that ability, insanity, temperament and personality all tended to run in families, just as physical traits like stature, complexion, hair and eye colour also do.[1]

However, while the discovery of a heritable component to character and ability merely confirms the conventional wisdom of an earlier age, another behavioural genetic finding, far more surprising and counterintuitive, has passed relatively unreported. 

This is the discovery that the so-called shared family environment (i.e. the environment shared by siblings, or non-siblings, raised in the same family home) actually has next to no effect on adult personality and behaviour. 

This we know from such classic study designs in behavioural genetics as twin studies, adoption studies and family studies.

In short, individuals of a given degree of relatedness, whether identical twins, fraternal twins, siblings, half-siblings or unrelated adoptees, are, by the time they reach adulthood, no more similar to one another in personality or IQ when they are raised in the same household than when they are raised in entirely different households. 

The Myth of Parental Influence 

Yet parental influence has long loomed large in virtually every psychological theory of child development, from the Freudian Oedipus complex and Bowby’s attachment theory to the whole literary genre of books aimed at instructing anxious parents on how best to raise their children so as to ensure that the latter develop into healthy, functional, successful adults. 

Indeed, not only is the conventional wisdom among psychologists overturned, but so is the conventional wisdom among sociologists – for one aspect of the shared family environment is, of course, household income and social class. 

Thus, if the family that a person is brought up in has next to no impact on their psychological outcomes as an adult, then this means that the socioeconomic status of the family home in which they are raised also has no effect. 

Poverty, or a deprived upbringing, then, has no effect on IQ, personality or the prevalence of mental illness, at least by the time a person has reached adulthood.[2]

Neither is it only leftist sociologists who have proved mistaken. 

Thus, just as leftists use economic deprivation as an indiscriminate, catch-all excuse for all manner of social pathology (e.g. crime, unemployment, educational underperformance) so conservatives are apt to place the blame on divorce, family breakdown, having children out of wedlock and the consequential increase in the prevalence of single-parent households. 

However, all these factors are, once again, part of the shared family environment – and according to the findings of behavioural genetics, they have next to no influence on adult personality or intelligence. 

Of course, chaotic or abusive family environments do indeed tend to produce offspring with negative life outcomes. 

However, none of this proves that it was the chaotic or abusive family environment that caused the negative outcomes. 

Rather, another explanation is at hand – perhaps the offspring simply biologically inherit the personality traits of their parents, the very personality traits that caused their family environment to be so chaotic and abusive in the first place.[3] 

For example, parents who divorce or bear offspring out-of-wedlock likely differ in personality from those who first get married then stick together, perhaps being more impulsive or less self-disciplined and conscientious (e.g. less able refrain from having children from a relationship that was destined to be fleeting, or less able to persevere and make the relationship last). 

Their offspring may, then, simply biologically inherit these undesirable personality attributes, which then themselves lead to the negative social outcomes associated with being raised in single-parent households or broken homes. The association between family breakdown and negative outcomes for offspring might, then, reflect simply the biological inheritance of personality. 

Similarly, as leftists are fond of reminding us, children from economically-deprived backgrounds do indeed have lower recorded IQs and educational attainment than those from more privileged family backgrounds, as well as other negative outcomes as adults (e.g. lower earnings, higher rates of unemployment). 

However, this does not prove that coming from a deprived family background necessarily itself depresses your IQ, educational attainment or future salary. 

Rather, an equally plausible possibility is simply that offspring simply biologically inherit the low intelligence of their parents – the very low intelligence which was likely a factor causing the low socioeconomic status of their parents, since intelligence is known to correlate strongly with educational and occupational advancement.[4]

In short, the problem with all of this body of research which purports to demonstrate the influence of parents and family background on psychology and behavioural outcomes for offspring is that they fail to control for the heritability of personality and intelligence, an obvious confounding factor. 

The Non-Shared Environment

However, not everything is explained by heredity. As a crude but broadly accurate generalization, only about half the variation for most psychological traits is attributable to genes. This leaves about half of the variation in intelligence, personality and mental illness to be explained environmental factors.  

What are these environmental factors if they are not to be sought in the shared family environment? 

The obvious answer is, of course, the non-shared family environment – i.e. the ways in which even children brought up in the same family-home nevertheless experience different micro-environments, both within the home and, perhaps more importantly, outside it. 

Thus, even the fairest and most even-handed parents inevitably treat their different offspring differently in some ways.  

Indeed, among the principal reasons why parents treat their different offspring differently is precisely because the different offspring themselves differ in their own behaviour quite independently of any parental treatment.

This is well illustrated by the question of the relationship between corporal punishment and behaviour in children.

Corporal punishment 

Rather than differences in the behaviour of different children resulting from differences in how their parents treat them, it may be that differences in how parents treat their children may reflect responses to differences in the behaviour of the children themselves. 

In other words, the psychologists have the direction of causation precisely backwards. 

Take, for example, one particularly controversial issue, namely the physical chastisement of children by their parents as a punishment for bad behaviour (e.g. spanking). 

Some psychologists have sometimes argued that physical chastisement actually causes misbehaviour. 

As evidence, they cite the fact that children who are spanked more often by their parents or caregivers on average actually behave worse than those whose caregivers only rarely or never spank the children entrusted to their care.  

This, they claim, is because, in employing spanking as a form of discipline, caregivers are inadvertently imparting the message that violence is a good way of solving your problems. 

Actually, however, I suspect children are more than capable of working out for themselves that violence is often an effective means of getting your way, at least if you have superior physical strength to your adversary. Unfortunately, this is something that, unlike reading, arithmetic and long division, does not require explicit instruction by teachers or parents. 

Instead, a more obvious explanation for the correlation between spanking and misbehaviour in children is not that spanking causes misbehaviour, but rather that misbehaviour causes spanking. 

Indeed, once you think about it, this is in fact rather obvious: If a child never seriously misbehaves, then a parent likely never has any reason to spank that child, even if the parent is, in principle, a strict disciplinarian; whereas, on the other hand, a highly disobedient child is likely to try the patience of even the most patient caregiver, whatever his or her moral opposition to physical chastisement in principle. 

In other words, causation runs in exactly the opposite direction to that assumed by the naïve psychologists.[5] 

Another factor may also be at play – namely, offspring biologically inherit from their parents the personality traits that cause both the misbehaviour and the punishment. 

In other words, parents with aggressive personalities may be more likely to lose their temper and physically chastise their children, while children who inherit these aggressive personalities are themselves more likely to misbehave, not least by behaving in an aggressive or violent manner. 

However, even if parents treat their different offspring differently owing to the different behaviour of the offspring themselves, this is not the sort of environmental factor capable of explaining the residual non-shared environmental effects on offspring outcomes. 

After all, this merely begs the question as to what caused these differences in offspring behaviour in the first place? 

If the differences in offspring behaviour exist prior to differences in parental responses to this behaviour, then these differences cannot be explained by the differences in parental responses.  

Peer Groups 

This brings us back to the question of the environmental causes of offspring outcomes – namely, if about half the differences among children’s IQs and personalities are attributable to environmental factors, but these environmental factors are not to be found in the shared family environment (i.e. the environment shared by children raised in the same household), then where are these environmental factors to be sought? 

The search for environmental factors affecting personality and intelligence has, thus far, been largely unsuccessful. Indeed, some behavioural geneticists have almost gone as far as conceding scholarly defeat in identifying correlates for the environmental portion of the variance. 

Thus, leading contemporary behavioural geneticist Robert Plomin in his recent book, Blueprint: How DNA Makes Us Who We Are, concludes that those environmental factors that affect cognitive ability, personality, and the development of mental illness are, as he puts it, ‘unsystematic’ in nature. 

In other words, he seems to be saying that they are mere random noise. This is tantamount to accepting that the null hypothesis is true. 

Judith Harris, however, has a quite different take. According to Harris, environmental causes must be sought, not within the family home, but rather outside it – in a person’s interactions with their peer-group and the wider community.[6]

Environment ≠ Nurture 

Thus, Harris argues that the so-called nature-nurture debate is misnamed, since the word ‘nurture’ usually refers to deliberate care and moulding of a child (or of a plant or animal). But many environmental effects are not deliberate. 

Thus, Harris repeatedly references behaviourist John B. Watson’s infamous boast: 

“Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.”

Yet what strikes me as particularly preposterous about Watson’s boast is not its radical environmental determinism, nor even its rather convenient unfalsifiability.[7] 

Rather, what most strikes me as most preposterous about Watson’s claim is its frankly breath-taking arrogance. 

Thus, Watson not only insisted that it was environment alone that entirely determined adult personality. In this same quotation, he also proclaimed that he already fully understood the nature of these environmental effects to such an extent that, given omnipotent powers to match his evidently already omniscient understanding of human development, he could produce any outcome he wished. 

Yet, in reality, environmental effects are anything but clear-cut. Pushing a child in a certain direction, or into a certain career, may sometimes have the desired effect, but other times may seemingly have the exact opposite effect to that desired, provoking the child to rebel against parental dictates. 

Thus, even to the extent that environment does determine outcomes, the precise nature of the environmental factors implicated, and their interaction with one another, and with the child’s innate genetic endowment, is surely far more complex than the simple mechanisms proposed by behaviourists like Watson (e.g. reinforcement and punishment). 

Language Acquisition 

The most persuasive evidence for Harris’s theory of the importance of peer groups comes from an interesting and widely documented peculiarity of language acquisition. 

The children of immigrants, whose parents speak a different language inside the family home, and may even themselves be monolingual, nevertheless typically grow up to speak the language of their host culture rather better than they do the language to which they were first exposed in the family home. 

Indeed, while their parents may never achieve fluency in the language of their host culture, having missed out on the Chomskian critical period for language acquisition, their children often actually lose the ability to speak their parent’s language, often much to the consternation of parents and grandparents. 

Yet, from an sociobiological or evolutionary psychological perspective, such an outcome is obviously adaptive. 

After all, if a child is to succeed in wider society, they must master its language, whereas, if their parent’s first language is not spoken anywhere in their host society except in their family, then it is of limited utility, and, once their parents themselves become proficient in the language of the host culture, it becomes entirely redundant.

As sociologist-turned-sociobiologist Pierre van den Berghe observes in his excellent The Ethnic Phenomenon (reviewed here):

“Children quickly discover that their home language is a restricted medium that not useable in most situations outside the family home. When they discover that their parents are bilingual they conclude – rightly for their purposes – that the home language is entirely redundant… Mastery of the new language entails success at school, at work and in ‘the world’… [against which] the smiling approval of a grandmother is but slender counterweight” (The Ethnic Phenomenon: p258). 

Code-Switching 

Harris suggests that the same applies to personality. Just as the child of immigrants switches between one language and another at home and school, so they also adopt different personalities. 

Thus, many parents are surprised to be told by their children’s teachers at parents’ evenings that their offspring is quiet and well-behaved at school, since, they report, he or she isn’t at all like that at home. 

Yet, at home, a child has only, at most, a sibling or two with whom to compete for his parents’ attention. In contrast, at school, he or she has a whole class with whom to compete for their teacher’s attention.

It is therefore unsurprising that most children are less outgoing at school than they are at home with their parents. 

For example, an older sibling might be able push his little brother around at home. But, if he is small for his age, he is unlikely to be able to get away with the same behaviour among his peers at school. 

Children therefore adopt two quite different personalities – one for interactions with family and siblings, and another for among their peers.

This then, for Harris, explains why, perhaps surprisingly, birth-order has generally been found to have little if any effect on personality, at least as personality manifests itself outside the family home. 

An Evolutionary Theory of Socialization? 

Interestingly, even evolutionary psychologists have not been immune from the delusion of parental influence. Thus, in one influential paper, anthropologists Patricia Draper and Henry Harpending argued that offspring calibrate their reproductive strategy by reference to the presence or absence of a father in their household (Draper & Harpending 1982). 

On this view, being raised in a father-absent household is indicative of a social environment where low male parental investment is the norm, and hence offspring adjust their own reproductive strategy accordingly, adopting a promiscuous, low-investment mating strategy characterized by precocious sexual development and an inability to maintain lasting long-term relationships (Draper & Harpending 1982; Belsky et al 1991). 

There is indeed, as these authors amply demonstrate, a consistent correlation between father-absence during development and both earlier sexual development and more frequent partner-switching in later life. 

Yet there is also another, arguably more obvious, explanation readily at hand to explain this association. Perhaps offspring simply inherit biologically the personality traits, including sociosexual orientation, of their parents. 

On this view, offspring raised in single-parent households are more likely to adopt a promiscuous, low-investment mating strategy simply because they biologically inherit the promiscuous sociosexual orientation of their parents, the very promiscuous sociosexual orientation that caused the latter to have children out-of-wedlock or from relationships that were destined to break down and hence caused the father-absent childhood of their offspring. 

Moreover, even on purely a priori theoretical grounds, Draper, Harpending and Belsky’s reasoning is dubious. 

After all, whether you personally were raised in a one- or two-parent family is obviously a very unreliable indicator of the sorts of relationships prevalent in the wider community into which you are born, since it represents a sample size of just one. 

Instead, therefore, it would be far more reliable to calibrate your reproductive strategy in response to the prevalence of one-parent households in the wider community at large, rather than the particular household type into which you happen to have been born.  

This, of course, directly supports Harris’s own theory of ‘peer group socialization’. 

In short, to the extent that children do adapt to the environment and circumstances of their upbringing (and they surely do), they must integrate into, adopt the norms of, and a reproductive strategy to maximize their fitness within, the wider community into which they are born, rather than the possibly quite idiosyncratic circumstances and attitudes of their own family. 

Absent Fathers, from Upper-Class to Under-Class 

Besides language-acquisition among the children of immigrants, another example cited by Harris in support of her theory of ‘peer group socialization’ is the culture, behaviours and upbringing of British upper-class males.

Here, she reports, boys were, and, to some extent, still are, reared primarily, not by their parents, but rather by nannies, governoresses and, more recently, in exclusive fee-paying all-male boarding schools. 

Yet, despite having next to no contact with their fathers throughout most of their childhood, these boys nevertheless managed somehow to acquire manners, attitudes and accents similar, if not identical, to those of their upper-class fathers, and not at all those of the middle-class nannies, governoresses and masters with whom they spent most of their childhood being raised. 

Yet this phenomenon is by no means restricted to the British upper-classes.

On the contrary, rather than citing the example of the British upper-classes in centuries gone by, Harris might just as well have cited that of contemporary underclass in Britain and America, since what was once true of the British upper-classes, is now equally true of the underclass. 

Just as the British upper-classes were once raised by governoresses, nannies and in private schools with next to no contact with their fathers, so contemporary underclass males are similarly raised in single-parent households, often to unwed mothers, and typically have little if any contact with their biological fathers. 

Here, as Warren Farrell observes in his seminal The Myth of Male Power (which I have reviewed here, here and here), there is a now a “a new nuclear family: woman, government and child”, what Farrell terms “Government as a Substitute Husband”. 

Yet, once again, these underclass males, raised by single parents with the financial assistance of the taxpayer, typically turn out much like their absent fathers with whom they have had little if any contact, often going on to promiscuously father a succession of offspring themselves, with whom they likewise have next to no contact. 

Abuse 

But what of actual abuse? Surely this has a long-term devastating psychological impact on children. This, at any rate, is the conventional wisdom, and questioning this wisdom, at least with respect to sexual abuse, is tantamount to contemporary heresy, with attendant persecution. 

Thus, for example, it is claimed that criminals who are abusive towards their children were themselves almost invariably abused, mistreated or neglected as children, which is what has led to their own abusive, behaviour.

A particularly eloquent expression of this theory is found in the novel Clockers, by Richard Price, where one of the lead characters, a police officer, explains how, during his first few years on the job, a senior colleague had restrained him from attacking an abusive mother who had left her infant son handcuffed to a radiator, telling him:

“Rocco, that lady you were gonna brain? Twenty years ago when she was a little girl. I arrested her father for beating her baby brother to death. The father was a piece of shit. Now that she’s all grown up? She’s a real piece of shit. That kid you saved today. If he lives that long, if he grows up? He’s gonna be a real piece of shit. It’s the cycle of shit and you can’t do nothing about it” (Clockers: p96).

Take, for example, what is perhaps the form of child abuse that provokes the most outrage and disgust – namely, sexual abuse. Here, it is frequently asserted that paedophiles were almost invariably themselves abused as children, which creates a so-called ‘cycle of abuse’. 

However, there are at least three problems with this claim. 

First, it cannot explain how the first person in this cycle came to be abusive. 

Second, we might doubt whether it is really true that paedophiles are disproportionately likely to have themselves been abused as children. After all, abuse is something that almost invariably happens surreptitiously ‘behind closed doors’ and is therefore difficult to verify or disprove. 

Therefore, even if most paedophiles claim to have been victims of abuse, it is possible that they are simply lying in order to elicit sympathy or excuse or shift culpability for their own offending. 

Finally, and most importantly for present purposes, even if paedophiles can be shown to be disproportionately likely to have themselves been victimized as children, this by no means proves that their past victimization caused their current sexual orientation. 

Rather, since most abuse is perpetrated by parents or other close family members, an alternative possibility is that victims simply biologically inherit the sexual orientation of their abuser.

After all, if homosexuality is partially heritable, as is now widely accepted, then why not paedophilia as well? 

In short, the ‘cycle of shit’ referred to by Price’s fictional police officer may well be real, but mediated by genetics rather than childhood experience.

However, this conclusion is not entirely clear. On the contrary, Harris is at pains to emphasize that the finding that the shared family environment accounts for hardly any of the variance in outcomes among adults does not preclude the possibility that severe abuse may indeed have an adverse effect on adult outcomes. 

After all, adoption studies can only tell us what percent of the variance is caused by heredity or by shared or unshared environments within a specific population as a whole.

Perhaps the shared family environment accounts for so little of the variance precisely because the sort of severe abuse that does indeed have a devastating long-term effect on personality and mental health is, thankfully, so very rare in modern societies. 

Indeed, it may be especially rare within the families sampled in adoption studies precisely because adoptive families are carefully screened for suitability before being allowed to adopt. 

Moreover, Harris emphasizes an important caveat: Even if abuse does not have long-term adverse psychological effects, this does not mean that abuse causes no harm, and nor does it in any way excuse such abuse. 

On the contrary, the primary reason we shouldn’t mistreat children (and should severely punish those who do) is not on account of some putative long-term psychological effect on the adults whom the children subsequently become, but rather because of the very real pain and suffering inflicted on a child at the time the abuse takes place. 

Race Differences in IQ 

Finally, Harris even touches upon that most vexed area of the (so-called) nature-nurture debate – race differences in intelligence. 

Here, the politically-correct claim that differences in intelligence between human races, as recorded in IQ tests, are of purely environmental origin runs into a problem, since the sorts of environmental effects that are usually posited by environmental determinists as accounting for the black-white test score gap in America (e.g. differences in rates of poverty and socioeconomic status) have been shown to be inadequate because, even after controlling for these factors, there remains a still unaccounted for gap in test-scores.[8]

Thus, as Arthur R. Jensen laments: 

“This gives rise to the hypothesizing of still other, more subtle environmental factors that either have not been or cannot be measured—a history of slavery, social oppression, and racial discrimination, white racism, the ‘black experience,’ and minority status consciousness [etc]” (Straight Talk About Mental Tests: p223). 

The problem with these explanations, however, is that none of these factors has yet been demonstrated to have any effect on IQ scores. 

Moreover, some of the factors proposed as explanations are formulated in such a vague form (e.g. “white racism, the ‘black experience’”) that it is difficult to conceive of how they could ever be subjected to controlled testing in the first place.[9]

Jensen has termed this mysterious factor the ‘X-factor’. 

In coining this term, Jensen was emphasizing its vague, mysterious and unfalsifiable nature. Jensen did not actually believe that this posited ‘X-factor’, whatever it was, really did account for the test-score gap. Rather, he thought heredity explained most, if not all, of the remaining unexplained test-score gap. 

However, Harris takes Jensen at his word and takes the search for the ‘X-factor’ very seriously. Indeed, she apparently believes she has discovered and identified it. Thus, she announces: 

“I believe I know what this X factor is… I can describe it quite clearly. Black kids and white kids identify with different groups that have different norms. The differences are exaggerated by group contrast effects and have consequences that compound themselves over the years. That’s the X factor” (p248-9). 

Unfortunately, Harris does not really develop this fascinating claim. Indeed, she cites no direct evidence in support of this claim, and evidently seems to regard the alternative possibility – namely, that race differences in intelligence are at least partly genetic in origin – as so unpalatable that it can safely ruled out a priori.

In fact, however, although not discussed by Harris, there is at least some evidence in support of her theory. Indeed, her theory potentially reconciles the apparently conflicting findings of two of the most widely-cited studies in this vexed area of research and debate.

First, in the more recent of these two studies, Minnesota Transracial Adoption Study, the same race differences in IQ were observed among black, white and mixed-race children adopted into upper-middle class white families as are found among black, white and mixed-race populations in the community at large (Scarr & Weinberg 1976). 

Moreover, although, when tested during childhood, the children’s adoptive households did seem to have had a positive effect on their IQ scores, in a follow-up study it was found that by the time they reached the cusp of adulthood, the black teenagers who had been adopted into upper-middle-class white homes actually scored no higher in IQ than did blacks in the wider population not raised in upper-middle class white families (Weinberg, Scarr & Waldman 1992). 

Although Scarr, Weinberg and Waldman took pains to present their findings as compatible with a purely environmentalist theory of race differences, this study has, not unreasonably, been widely cited by hereditarians as evidence for the existence of innate racial differences in intelligence (e.g. Levin 1994; Lynn 1994; Whitney 1996).

However, in the light of the findings of the behavioural genetics studies discussed by Harris in ‘The Nurture Assumption’, the fact that white upper-middle-class adoptive homes had no effect on the adult IQs of the black children adopted into them is, in fact, hardly surprising. 

After all, as we have seen, the shared family environment generally has no effect on IQ, at least by the time the person being tested has reached adulthood.[10]

One would therefore not expect adoptive homes, howsoever white and upper-middle-class, to have any effect on adult IQs of the black children adopted into them, or indeed of the white or mixed-race children adopted into them. 

In short, adoptive homes have no effect on adult IQ, whether or not the adoptees, or adoptive families, are black, white, brown, yellow, green or purple! 

But, if race differences in intelligence are indeed entirely environmental in origin, then where are these environmental causes to be found, if not in the family environment? 

Harris has an answer – black culture. 

According to her, the black adoptees, although raised in white adoptive families, nevertheless still come to identify as ‘black’, and to identify with the wider black culture and social norms. In addition, they may, on account of their racial identification, come to socialize with other blacks in school and elsewhere. 

As a result of this acculturation to African-American norms and culture, they therefore, according to Harris, come to score lower in IQ than their white peers and adoptive siblings. 

But how can we ever test this theory? Is it not untestable, and is this not precisely the problem identified by Jensen with previous posited ‘X-factors’.

Actually, however, although not discussed by Harris, there is a way of testing this theory – namely, looking at the IQs of black children raised in white families where there is no wider black culture with which to identify, and few if any black peers with whom to socialize?

This, then, brings us to the second of the two studies which Harris’s theory potentially reconciles, namely the famous Eyferth study.  

Here, it was found that the mixed-race children fathered by black American servicemen who had had sexual relationships with German women during the Allied occupation of Germany after World War Two had almost exactly the same average IQ scores as a control group of offspring fathered by white US servicemen during the same time period (Eyferth 1959). 

The crucial difference from the Minnesota study may be that these children, raised in an almost entirely monoracial, white Germany in the mid-twentieth century, had no wider African-American culture with which to identify or whose norms to adopt, and few if any black or mixed-race peers in their vicinity with whom to socialize. 

This, then, is perhaps the last lifeline for a purely environmentalist theory of race differences in intelligence – namely the theory that African-American culture depresses intelligence. 

Unfortunately, however, this proposition – namely, that African-American culture depresses your IQ – is almost as politically unpalatable and politically-incorrect as is the notion that race differences in intelligence reflect innate genetic differences.[11]

Endnotes

[1] Thus, this ancient wisdom is reflected, for example, in many folk sayings, such as ‘the apple does not fall far from the tree’, ‘a chip off the old block’ and ‘like father, like son’, many of which long predate either Darwin’s theory of evolution, and Mendel’s work on heredity, let alone the modern work of behavioural geneticists.

[2] It is important to emphasize here that this applies only to psychological outcomes, and not, for example, economic outcomes. For example, a child raised by wealthy parents is indeed likely to be wealthier than one raised in poverty, if only because s/he is likely to inherit (some of) the wealth of his parents. It is also possible that s/he may, on average, obtain a better job as a consequence of the opportunities opened by his privileged upbringing. However, his IQ will be no higher than had s/he been raised in relative poverty, and neither will s/he be any more or less likely to suffer from a mental illness. 

[3] Similarly, it is often claimed that children raised in care homes, or in foster care, tend to have negative life-outcomes. However, again, this by no means proves that it is care homes or foster care that causes these negative life-outcomes. On the contrary, since children who end up in foster care are typically either abandoned by their biological parents, or forcibly taken from their parents by social services on account of the inadequate care provided by the latter, or sometimes outright abuse, it is obvious that their parents represent an unrepresentative sample of society as a whole. An obvious alternative explanation, then, is that the children in question simply inherit the dysfunctional personality attributes of their biological parents, namely the very dysfunctional personality attributes that caused the latter to either abandon their children or have them removed by the social services. (In other cases, such children may have been orphaned. However, this is less common today. At any rate, parents who die before their offspring reach maturity are surely also unrepresentative of parents in general. For example, many may live high-risk lifestyles that contribute to their early deaths.)

[4] Likewise, the heritability of such personality traits as conscientiousness and self-discipline, in addition to intelligence, likely also partly account for the association between parental income and academic attainment among their offspring, since both academic attainment, and occupational success, require the self-discipline to work hard to achieve success. These factors, again in addition to intelligence, likely also contribute to the association between parental income and the income and socioeconomic status ultimately attained by their offspring.

[5] This possibility could, at least in theory, be ruled out by longitudinal studies, which could investigate whether the spanking preceded the misbehaviour, or vice versa. However, this is easier said than done, since, unless relying on the reports by caregivers or children themselves, which depends on both the memory and honesty of the caregivers and children themselves, it would have to involve intensive, long-term, and continued observation in order to establish which came first, namely the pattern of misbehaviour, or the adoption of physical chastisement as a method of discipline. This would, presumably, require continuous observation from birth onwards, so as to ensure that the very first instance of spanking or excessive misbehaviour were recorded. Such a study would seem all but impossible and certainly, to my knowledge, has yet to be conducted.

[6] The fact that the relevant environmental variables must be sought outside the family home is one reason why the terms ‘between-family environment’ and ‘within-family environment’, sometimes used as synonyms or alternatives for ‘shared’ and ‘non-shared family environment’ respectively, are potentially misleading. Thus, the ‘within-family environment’ refers to those aspects of the environment that differ for different siblings even within a single family. However, these factors may differ within a single family precisely because they occur outside, not within, the family itself. The terms ‘shared’ and ‘non-shared family environment’ are therefore to be preferred, so as to avoid any potential confusion these alternative terms could cause.

[7] Both practical and ethical considerations, of course, prevent Watson from actually creating his “own specified world” in which to bring up his “dozen healthy infants”. Therefore, no one is able to put his claim to the test. It is therefore unfalsifiable and Watson is therefore free to make such boasts, safe in the knowledge that there is no danger of his actually being called to make good on his claims and thereby proven wrong.

[8] Actually, even if race differences in IQ are found to disappear after controlling for socioeconomic status, it would be a fallacy to conclude that this means that the differences in IQ are entirely a result of differences in social class and that there is no innate difference in intelligence between the races. After all, differences in socioeconomic status are in large part a consequence of differences in cognitive ability, as more intelligent people perform better at school, and at work, and hence rise in socioeconomic status. Therefore, in controlling for socioeconomic status, one is, in effect, also controlling for differences in intelligence, since the two are so strongly correlated. The contrary assumption has been termed by Jensen ‘the sociologist’s fallacy’.
This fallacy involves the assumption that it is differences in socioeconomic status that cause differences in IQ, rather than differences in intelligence that cause differences in socioeconomic status. As Arthur Jensen explains it:

“If SES [i.e. socioeconomic status] were the cause of IQ, the correlation between adults’ IQ and their attained SES would not be markedly higher than the correlation between children’s IQ and their parents’ SES. Further, the IQs of adolescents adopted in infancy are not correlated with the SES of their adoptive parents. Adults’ attained SES (and hence their SES as parents) itself has a large genetic component, so there is a genetic correlation between SES and IQ, and this is so within both the white and the black populations. Consequently, if black and white groups are specially selected so as to be matched or statistically equated on SES, they are thereby also equated to some degree on the genetic component of IQ” (The g Factor: p491).

[9] Actually, at least some of these theories are indeed testable and potentially falsifiable. With regard to the factors quoted by Jensen (namely, “a history of slavery, social oppression, and racial discrimination, white racism… and minority status consciousness”), one way of testing these theories is to look at test scores in those countries where there is no such history. For example, in sub-Saharan Africa, as well as in Haiti and Jamaica, blacks are in the majority, and are moreover in control of the government. Yet the IQ scores of the indigenous populations of sub-Saharan Africa are actually even lower than among blacks in the USA (see Richard Lynn’s Race Differences in Intelligence: reviewed here). True, most such countries still have a history of racial oppression and discrimination, albeit in the form of European colonialism rather than racial slavery or segregation in the American sense. However, in those few sub-Saharan African countries that were not colonized by western powers, or only briefly colonized (e.g. Ethiopia, Liberia), scores are not any higher. Also, other minority groups ostensibly or historically subject to racial oppression and discrimination (e.g. Ashkenazi Jews, Overseas Chinese) actually score higher in IQ than the host populations that ostensibly oppress them. As for “the ‘black experience’”, this meanly begs the question as to why the ‘black experience’ has been so similar, and resulted in the same low IQs in so many different parts of the world, something implausible unless unless the ‘black experience’ itself reflects innate aspects of black African psychology. 

[10] The fact that the heritability of intelligence is higher in adulthood than during childhood, and the influence of the shared family environment correspondingly decreases, has been interpreted as reflecting the fact that, during childhood, our environments are shaped, to a considerable extent, by our parents. For example, some parents may encourage activities that may conceivably enhance intelligence, such as reading books and visiting museums. In contrast, as we enter adulthood, we begin to have freedom to choose and shape our own environments, in accordance with our interests, which may be partly a reflection of our heredity.
Interestingly, this theory suggests that what is biologically inherited is not necessarily intelligence itself, but rather a tendency to seek out intelligence-enhancing environments, i.e. intellectual curiosity rather than intelligence as such. In fact, it is probably a mixture of both factors. Moreover, intellectual curiosity is surely strongly correlated with intelligence, if only because it requires a certain level of intelligence to appreciate intellectual pursuits, since, if one lacks the ability to learn or understand complex concepts, then intellectual pursuits are necessarily unrewarding.

[11] Thus, ironically, the recently deceased James Flynn, though always careful, throughout his career, to remain on the politically-correct radical environmentalist side of the debate with regard to the causes of race differences in intelligence, nevertheless recently found himself taken to task by the leftist, politically-correct British Guardian newspaper for a sentence in his recent book, Does Your Family Make You Smarter, where he described American blacks as coming from a “from a cognitively restricted subculture” (Wilby 2016). Thus, whether one attributes lower black IQs to biology or to culture, either answer is certain offend leftists, and the power of political correctness can, it seems, never be appeased.

References 

Belsky, Steinberg & Draper (1991) Childhood Experience, Interpersonal Development, and Reproductive Strategy: An Evolutionary Theory of Socialization Child Development 62(4): 647-670 

Draper & Harpending (1982) Father Absence and Reproductive Strategy: An Evolutionary Perspective Journal of Anthropological Research 38:3: 255-273 

Eyferth (1959) Eine Untersuchung der Neger-Mischlingskinder in Westdeutschland. Vita Humana, 2, 102–114

Levin (1994) Comment on Minnesota Transracial Adoption Study. Intelligence. 19: 13–20

Lynn, R (1994) Some reinterpretations of the Minnesota Transracial Adoption Study. Intelligence. 19: 21–27

Scarr & Weinberg (1976) IQ test performance of black children adopted by White families. American Psychologist 31(10):726–739 

Weinberg, Scarr & Waldman, (1992) The Minnesota Transracial Adoption Study: A follow-up of IQ test performance at adolescence Intelligence 16:117–135 

Whitney (1996) Shockley’s experiment. Mankind Quarterly 37(1): 41-60

Wilby (2006) Beyond the Flynn effect: New myths about race, family and IQ? Guardian, September 27.