The realist position about g ; critics confounded.
Why g nevertheless gets lost by psychologists.
Advantages of re-discovery of the g factor.
Despite hopes of banishing philosophy from its chosen terrain, twentieth-century psychology has remained a quasi-philosophical battleground. Striving to exorcize the abstract and the unobservable from psychology, behaviourists and their modern descendants in cognitive science border on 'epiphenomenalism' about the mind/body problem: they may allow that distinct, non-material mentality results mysteriously (or, as is said, 'emerges') from matter (i.e. from the brain); but they are unhappy discussing the measurable realities or the causal influences of mental processes and proclivities themselves. In contrast, uninhibited by the self-denying ordinances of empiricism and behaviourism (which hold all abstract processes to derive from external referents), today's constructivists in developmental and social psychology assume that the only reality that we can know is social, ideational or linguistic. For them, genes, brains, mentality and mental powers are just bundles of terms thrown up in the course of human word games; and the language of 'mind' serves only the political purpose of establishing control of discourse and thus of life. On the one hand, the exponents of mind-body functionalism(1) say they would cheerfully attribute consciousness, intelligence and volition to a robot that could perform a few tricks of apparent 'representation' from some yet-to-be-written list. (The most humdrum feats of machine translation encourage them to believe that some kind of 'representation' simply must have occurred.(2)) On the other hand, their mirror-image bedfellows in modern idealism would attribute as much meaning and intelligence to the 'text' of a party political broadcast or diet advertisement as they would to the ideas ('rhetoric') and mental faculties of an actual human bein g ; and these constructivists would hope to appeal to Wittgenstein for a demonstration that there is, anyhow, no way out of the language games that enmesh us.
Rejecting these quasi-philosophical programmes, with their tendencies to reduce human mentality to bits of hard- or software or to snippets of discourse, the realists of differential psychology (and most especially of the London School) have insisted on three postulates.
- The fully biosocial nature of a person.
- The equally real existence of both mind and body.
- The ability of psychology to achieve significant purchase on mental phenomena and mental differences by means that are at once genuinely objective and passably quantitative.
It is to be hoped that no one would expect a differential psychologist to solve 'the mind-body problem' - to explain how these two great realms of reality interact with each other as they do so especially yet so puzzlingly within the human person.(3) There is certainly no need to do so while cognitivists and constructivists simply decline to discuss mentality at all. Workaday scientists successfully describe and quantify, discover patterns, and provide modest explanations of other events and enduring realities. Perhaps London School psychologists can hope to do likewise in the realm of mentality while other mysteries wait their turn?
Even a modest realism about g enrages those who have made it their business to rail against the g factor. By the end of his spirited critique of IQ testing, Stephen Gould (1981) turned out to have big surprises for his readers. It transpired that he had after all no fundamental objection to 'reifying' those six-to-eight mental abilities that had once been proposed by Thurstone; indeed, he could even tolerate providing heritability estimates for them and talking about them 'pessimistically' as barely open to therapeutic modification. Yet, even after abandoning the philosophical stance that he had seemed to adopt in the first three quarters of his book, Gould felt obliged to draw the line at accepting a reified, heritable, none-too-changeable g factor. Perhaps more consistently, Steven Rose (1995) continues a wider campaign against mental realism and continues to execrate reification of any kind: "Reification [whether of homosexuality, intelligence or aggression] converts a dynamic process into a static phenomenon.... If intelligence is one thing, it becomes appropriate to seek a single causative agent... We must abandon the unidirectional view of the causes of human action." It is certainly a mark of the seriousness of purpose of a critic of g that he would even suspend the forward direction of causality and replace it with a pantomime horse.
There is just one serious point in the writings of Gould and Rose on psychological matters - once what constructivists would properly call their 'rhetoric' is set aside. Both Gould and Rose are shocked at the prospect of a deterministic account of g that makes what they consider too little allowance for how interactive, as-yet-unrecognized parameters of influence on IQ could be changed. Yet this is strangely self-denying. First, it makes psychology a hostage to the undiscovered future. - Whereas, if it had to be guessed, the next century of data on g will most likely yield results broadly similar to those of the past. Secondly, the proper concern of Gould and Rose for human potential is strangely selective. It misses precisely those actual potentials for academic and moral growth that attention to the reality of g might already help to develop. Far from spreading gloom and despondency, to establish the reality of g is to clear a base for sensible and effective human choice: g's reality begins to define and clarify the real individuality of people; and it shows people and their would-be improvers where to start.
Some will say that the cause of 'realism' about the human mind and the human person is but poorly served by the psychology of IQ. The IQ movement of psychometric psychology originated in Victorian elitism, it may be said. It avoided entanglement with Nazi-style statism and racism principally because Hitler banned the use of tests on which Jews did well. The London School's mid-century failure to identify elementary bases and correlates of intelligence robbed it of the appurtenances of science, so it had to lean especially on genetics. And then there was the sorry farce as its leading mid-century luminary scoured his attic and his coal-hole in the hope of finding for callers vital data on the most fully separated monozygotic twins to have featured in the scientific record. Yet such embarrassments meet their match in behaviourist and constructivist psychology. These other psychological approaches have readily rejoiced in the centrality of the state to human nature and in the state's social-engineering powers. The no-human-nature egalitarianism of many of their practitioners has thus been deeply embarrassed by the collapse of Marxist utopias in Eastern Europe - providing a decisive result in "one of history's largest social experiments"(Bouchard, 1995). It is the one-time heroes of historical materialism and nature-denying existentialism, not those of differential psychology, who, as national leaders, have killed millions of their own people (Mao, Pol Pot) and, as psychologists, attracted criminal convictions and prison sentences for fraud (the Milwaukee Head Start practitioners). The explanatory achievements of behaviourism and constructivism that are hard to recall despite these perspectives enjoying years of popularity among the intelligentsia (accompanied by multi-billion dollar expenditures on behaviourism and its cognitivist successor). Above all, psychologists who have spurned the g factor have been guilty of creating a Western equivalent of the "ideological pseudo-reality" that Vaclav Havel and others exposed in communist Eastern Europe. By a 'collective fraud' (Gottfredson, 1994), they have condemned scientists and students, as Havel put it, to "live within a lie." Between them, psychology's inheritors of empiricism and idealism deny that much is known about the causes of unemployment, crime, welfare-dependency and the neglect and abuse of children: they betray people and psychology for the sake of another research grant.
In science, however, it is human achievements that count, not human weaknesses. So long as the measures and researches of science are not actually prohibited, science is naturally self-correcting. This has been the strength of the London School tradition. Spearman's successors have drawn upon, reinterpreted and integrated even the divergent achievements (and the still more divergent opinions) of Binet, Piaget, Schiff and Flynn (see Chapters I - IV respectively). The London School has articulated and developed methods of checking for 'bias' in tests, for the 'differentiation' of intelligence at higher g levels, and for the relation of g to personality. It has refined Spearman's early appreciation of the elementary bases of g and of how people cause their own environments (including others' attitudes to them) and thus express and develop their own real natures (as Aristotle first envisaged). It has continued and updated a way of describing and explaining human psychological realities that has provided the only robust, consistent and essentially unchanged psychology of the century. Throughout, it has seemed lastingly relevant to the liberation of children and adults from the similitarianism that is the sorry hallmark of much state intervention in human affairs. And the new understanding of the basic nature of intelligence may even help to explain and justify the common idea that human intelligence exceeds that of animals: perhaps this popular understanding is just a rough extrapolation from the idea that intelligence is concerned with 'extracting information', even if what animals lack is not intake speed itself but the ability to enhance intake enormously by loading information into handy symbols? (A similar claim of twentieth-century development-with-continuity might be made for the ideas of Freud. However, most modern psychoanalysts are actually disloyal to Freud's stress on the centrality of sex and sex differences; and Freud's followers, unlike Galton's, never solved the problem of how to measure the key Freudian process of repression - thus preventing satisfactory quantification and evaluation of many other Freudian proposals.)
This book has set out the progress that has been made, despite failings from within and rage from without, in tackling the problems that were defined yet left as challenges by Galton and Spearman. Despite repeated sallies by experts in education, genetics, palaeontology, anthropology and nuclear physics, and despite the indifference of sociologists, social anthropologists and philosophers, conventional tests of general intelligence have not needed to have their moulds broken. Mental tests have proved reliable, predictive, fair to minorities and frankly a model of the sensitive, objective and professional yet data-seeking approach to people in times when so much else in psychology has little but buzz-words and platitudes to offer. To ceaseless criticism that 'nobody knows what intelligence really is', the tests have provided a direct answer in the g factor that - as seen in its correlations - varies so little from one set of superficially diverse tests to another. More than that, the tests have realized the dreams of Galton and Spearman that, not too far beneath the complexities of everyday experience and valued abilities, some simpler strands of psychology might be discovered. Again, overcoming a century of feigned indifference to 'nature-nurture debates', psychogeneticists in the USA have been able to deploy the only long-term explanatory methods that human psychology has ever had, viz. those of twin and adoption study; and the result has been a decisive confirmation of a high heritability for g across a normal range of environments. Modern psychotelic investigation has confirmed the importance of IQ to adult lifestyles and self-made life chances. Most practically of all, there emerge reasons for allowing school pupils a choice of classroom difficulty levels; and, despite official indifference, there is mounting evidence that g-adjusted curricula are more effective and better enjoyed - even when children of different chronological ages are thus taught together.
In these pages, IQ - or, more precisely, the g factor - has thus proved to be a well-established variable in the realm of mentality. Many aspects of 'mind' are doubtless subtle and fleetin g ; and some are perhaps best left to the speculations and musings of philosophers and aesthetes. However, such scholars have not proved able to supply either evidence or arguments to rout the modern descendants of empiricism and idealism in psychology. Fortunately, on this psychological battlefield, little g is the Mighty Mouse - for all that sensitive souls may prefer to watch another match!
A wider question nevertheless remains for the overview of the psychology of intelligence that has been presented in this book. How can an aspirant science lose track of its main measurable variable? If the London School's account of g is indeed broadly correct and increasingly vindicated, why is IQ not standardly assessed in virtually all psychological research projects? How can a popular college subject like psychology have palmed off its students with the pursuit of a 'cognitive psychology' that has no theory of thought to its name and a social psychology that rejects measurement altogether? How can many modern psychologists have spent their time studying mainly subjects of above-average IQ, have pretended to themselves and their students that g differences did not exist, and yet have avoided professional malpractice suits for such neglect? How could Burt's establishment of educational psychology to guide remediation and tailored teaching have been spurned by psychologists just as by educationists? How could psychologists have come to favour studying the rat and the sophomore and, today, the computer, "virtual" reality and prospectively intelligent robots? Sadly, the following answers that can be offered to these questions are not very glorious; but at least the discoveries outlined in this book provide not just signposts but super-highways to a brighter future.
- Personal reasons: bowing to wishful thinking. Towards the end of the behaviourist era in psychology, the American psychometrician-psychologist, Quinn McNemar (1961), queried why intelligence had been "lost" from the repertoire of academic psychology. It was not long before he received an answer - from the silence of the many psychologists who did nothing to defend (or even to correct) Arthur Jensen's explanation of why Operation Headstart was failing. McNemar's question is worth repeating. Today, psychology has moved very far from the empiricism that had to prove everything tangibly and trace all psychological processes to observables: today, plenty of psychologists embrace the largely truth-free concerns of quasi-idealism, constructivism and 'discourse analysis'. What remains of science in psychology is chiefly a 'cognitive science' that seeks its metaphors of the human mind in robots which elude invention or demonstration but which are still put forward in grant proposals as able to provide a slave class for the future. Today, psychology's central doctrines are that everything is invented (social psychology) or that it soon will be invented (cognitive science). However, such guiding fictions are neither of them so far from the traditional aspirations of the behaviourist. In the early days of Watson and Skinner, former psychology and philosophy, and notions of consciousness and the unconscious, could be discarded; and it was expected that rigorous, abstraction-free laws of learning would soon enable the utopian transformation of mankind. Today the denial of human individuality in intelligence serves the same function. Russia under communism enforced Lysenko's 'genetics' whereby strains of wheat could supposedly adapt to being planted in winter, change their germ lines, and thus pass on their acquired learning to the next generation: Lysenko's revival of Lamarck's discredited ideas triumphed over the genetics of Darwin and Mendel because it suited the utopian Communist ideology that nature could readily be changed for the better. Western psychologists' acceptance of their own society's febrile optimism is certainly one part of the story of how g is forced off the stage - today as much as was noticed by McNemar. Instead of rising to the challenge of real human nature, many psychologists have preferred piety.
- Philosophical reasons: bowing to behaviourism. Despite its pretensions to independence, psychology is still beset by the problems of theology and philosophy from which many psychologists - beginning with John Watson - thought it would provide an escape. Through much of the twentieth century, psychologists felt obliged to accept the stern disciplines of philosophical empiricism and positivism: since they did not accept the Church or Scripture as authorities on human nature, psychologists wanted to show that they had equally demanding, objective and public criteria of their own as to what counted as truth. When empiricism and positivism were installed in psychology by the behaviourists, they provided less an Occam's razor than a chain-saw. IQ-type abilities had to be nothing but assemblies of relatively simple learned routines which, once their identification was complete, could surely be improved piecemeal in programmes of the Headstart type. IQ would thus fractionate on scientific analysis, just as the human mind, heart, soul and spirit were expected to be chopped into manageable pieces that might even be force-fed successfully to a thorough-going materialist.
Today's psychology offers plenty of liberation from the behaviourists' proper concern with objective evidence. Early cognitivism first extended behaviourist disintegrative aspirations while relaxing the key restriction that all learning could be reduced to the specifiable types of conditioning (which restriction had provided the central discipline of behaviourism). Cognitivism took an equally disunitarian view of intelligence yet dropped behaviourist restraints. Soon cognitivism would be found retreating behind flimsy barricades of nativism: cognitivists usually admit an innate 'language acquisition device' though they have much less to say about it than Spearman had to say about g. Again, cognitivism notoriously tolerates minimally specified 'black boxes' for its ever-changing number of 'memory stores': the case for the reality of g is far stronger than that for the existence of any supposed 'type' of human memory. Other psychologists feel increasingly free to talk of self-images, identities, and the infant's theory of mind. Yet, far from psychologists growing in confidence about their new subject matter, there seems to be a feeling that the escape from empiricism will be short-lived. (No doubt this is partly because little measurement of anything is achieved by the liberated.) Strange as it may seem, behaviourism itself has reappeared in the popular idealist insistence that there is nothing beyond or behind people's behaviour, talk or (as is fashionably said) 'texts'. As if fearing the behaviourist's scorn for abstraction and mentalism, the modern social psychologist simply avoids talk of ideas as well as mental realities - just like a behaviourist! In social psychology, the official end of behaviourism has yielded not realism but relativism - a refusal to accept that there are any truths at all about what people are really like. Piaget's modest rendering of intellectual development as a story of 'construction' was the previous high peak of idealism in psychology; but this is now far exceeded by social psychologists who reach back to Giovanni Battista Vico (1668-1744) for the view that truth and reality themselves are nothing but 'social constructions'. Thus the attempts of modern psychologists at empiricism and idealism have influenced discussions of intelligence; and served in particular to distract psychologists from the realism that is obviously the method-of-choice for handling a variable as measurable, as externally correlated and as well understood as g. Today, after prolonged flight from the measurable, it is time for psychologists to appreciate that the end of behaviourism allows quite as much room for the realism of Darwin, Galton and Burt as it does for the relativism of Vico, Nietzsche and Sartre.
- Practical reasons: bowing to convenience. A third reason for psychology's tendency to lose touch with intelligence is practical. Psychology's perennial problem is that of finding subjects who can be tested relatively cheaply. Medicine solves this problem by using patients in hospital beds who will often co-operate with research while they hope for treatment. Behaviourists solved the problem by studying rats; Piagetians solved it by studying infants; and cognitivists and the more advanced constructivists of social psychology solve it by hardly studying people at all - just building their computer 'models' or 'analysing' passages of 'discourse' selected for their ideological convenience. Clearly, differerential psychology should have followed Burt down the road to regular involvement in schools that he had opened up: most psychology departments should probably be located in or near a school - just as most medical faculties adjoin hospitals. But differential psychology and personality psychology rejected Burt's lead and chose for too long the superficially academic route of keeping up with the latest alleged advances in conditioning theory, 'social perception' or fissiparative neuropsychology. Thus differential psychology lost its natural subjects. This was disastrous for the study of g differences. It is only in normal schools that it is at all easy to study anything like the full range of human mental abilities. Many kinds of merely academic psychology can be done in the laboratory or in projects with handy collections of patients or employees (where selection, self-selection and resulting range-restrictions may be positive assets to the researcher of group effects). In contrast, the differential psychologist without a normal school with a full range of abilities will hardly ever see a correlation in excess of .40 between variables - let alone be able to examine it with colleagues and students who have a wider familiarity with the same testees and the same tests. The simple result is that there is all too little good data to discuss. Nor do brief social surveys help. Only sheer accident remedies the domination of education and social survey work by bureaucrats who find it politic to view social class as their key variable: it was simply the US Army's desire to keep its test-norms up-to-date that enabled Herrnstein & Murray's (1994) unprecedented exploration of the psychotelics of intelligence which has probably buried social class for the foreseeable future.
- Political reasons: bowing to the powers that be. A lack of good-quality data in differential psychology is precisely what some utopian idealists would wish. However, anti-realism usually involves more than happy fantasizing: there is usually a clear political agenda, of whatever 'left', 'right' or 'national redemption' origins. Support for anti-realism may stem from the left-wing belief in an equal world kept equal by state-funded experts in welfare redistributing the profits of such enterprise as is allowed; it may derive from a right-wing belief that most people can make a success of their local cultural tradition and the capitalist system if only they will work hard and behave themselves; or it may express a neo-fascist contempt for free-thinking artists, for intellectuals and for researchers who provide insufficient disparagement of enough minority groups and foreigners. Whatever the type of political encouragement, the resulting political meddling in education by ideologues results in neglect of intelligence and of children's proper education. Most children need specialized as well as generalist education if they are to be employable; they need skill in the received forms of their own language; they need to know the major languages of the regions in which they will do business, take holidays and have voting rights; and they require education at difficulty levels that are suitable for each of them in view of their IQ's and previous attainments. The taking of IQ's allows proper assessment of which educational methods and which teachers produce 'value-added' effects (on top of the progress that can be expected from children's IQ's alone). For precisely this reason, the taking of IQ' s is spurned by politicians and teachers' trade unions. The high water mark of such unrealism is provided by the banning of IQ testing, the insistence on mixed-ability 'teaching' and by the programmes of 'affirmative action' (i.e. compulsory discrimination) in the USA. Astonishingly, most Western countries' records of their schoolchildren today contain more about the children's teeth than about their intelligence. Psychologists have not even taken a back seat in opposing the unjust and unproductive egalitarianism which swept to institutional power as a handy new rhetoric in the nineteen-sixties. Never before can psychologists have proved so shamelessly sycophantic to the powers of the day!(4)
Thus it is that psychologists are, at best, divided about their subject's most popular, most predictive and most theoretically central variable. Social anthropologists believe human social phenomena are largely explicable in terms of systems of culture and kinship; classical Marxist sociologists think social class provides the explanation of a great part of the variance between people in how they live and who they think they are; geneticists are interested in what genes do; biologists study what living cells do; chemistry is about what atoms do; and physicists invoke sub-atomic particles. Yet what of psychologists? What are they interested in? How do they propose to explain their data on human behaviour and experience? To what key concepts will they repeatedly refer? After a century of coarse empiricism and relativistic idealism, it would be asking too much to expect that psychologists could be interested in 'the mind': that option would presumably be far too vague, far too reductionist, or both. Even such a familiar proposal as Freud's as to the mind's major components and levels of consciousness finds no general acceptance in psychology textbooks. It might have been thought that the concept of intelligence would provide at least a partial substitute - especially when general intelligence proves so easy to measure and so far-reaching as a predictor. Funnily enough, the idea that psychology is centrally concerned with 'cognition' has indeed appealed - even though virtually nothing of what cognitive scientists actually do answers interesting questions about what people think or why they think it. For the personal, philosophical, practical and political reasons indicated, intelligence is neglected. As Charles Murray (1992) has put it: "....there is an elephant sitting in the corner, which we have been trying to ignore for 30 years now."
If only a half of what has been said in this short exposition is true, rediscovering intelligence will yield substantial practical and humanitarian gains. The result-oriented human endeavours that have been most successful this century are probably those of business, the military and medicine. In all these fields individual differences are taken extremely seriously. James Flynn may have been somewhat misled by Army data as to the extent and significance of inter-generational changes that he took to disprove the importance of g. But Project Alpha on the US Army provided the largest-ever trial of psychologists' capacity to help with effective and fair selection, and the most complete resultant vindication of IQ testin g ; and Herrnstein & Murray's US Department of Defense data have shown that, in today's conditions, IQ differences are much more predictive than anything to do with young adults' social classes of origin. In future, the need to adapt education and training to individual differences - first and foremost in g - will be increasingly embedded within educational efforts (especially once tailored, computerized instruction becomes at long last a normal educational option). Still greater gains can also be expected from the liberation of schoolchildren from chronological-ageism with which the arguments of Chapter 4 should assist.(5)
There is probably much room for an individualization of state provision that may release human forces as dynamic as does the interplay between supply and demand in free markets. Today, liberal capitalism has emerged triumphant from a century of horrors: but liberalism and capitalism are not themselves dynamic doctrines that say much about what the state should do. Rather, their strength is to spell out what not to do and thus to unleash the forces of human individuals and their stored knowledge. It is time to realize that many features of individuality are quite unharnessed by state endeavours at present, even though state activity consumes around 40% of GNP in the West. As a test, individualizing state education according to intelligence and personal choice would show the way to a world in which the tyranny of states and their low-IQ local authorities was less feared. If the g factor were allowed its full play in schools, standards would rise rapidly and the real bases of achievement, creation, discovery and progress would be plain - in the human individual operating in conditions of freedom and dignity.
Success would blaze a trail to increased political freedom. In particular, the use of referenda (for long the most obvious way of extending democracy) might be accompanied by the further democratic advance of letting people themselves specify how their individual tax contributions be spent so long as they can demonstrate relevant knowledge. Letting people 'hypothecate' their taxes and vote on specific issues if they had relevant knowledge would similarly harness intelligence to politics.
Re-uniting psychology with education and with the cause of choice would realize Sir Cyril Burt's well-informed ambitions (however cavalierly pursued) and justify Arthur Jensen's persistence and his astonishing feats of martyred scholarship. It would also reassure Hans Eysenck and other loyalists of the London School. The realism that psychology must regain may have to override behaviourist dismissal of the existence of abstractions; but it can and must involve full commitment to inductive methods and data-gathering. For the desiderata of education and choice equally require constant study. Achieving them depends upon objective assessment of the real differences that psychological science and psychological testing disclose. The concept of general intelligence itself emerged from data, and not from 'definitions' or the preconceptions of psychologists; and the outlawing of the use of IQ measures came as second nature to the twentieth century despots - tinpot and otherwise - who hoped people would forget the facts. Far from being an invention of educational elitists, the g factor is a reality discovered by science; yet egalitarian envy of excellence has meant that the discovery has yet to be harnessed to the advantage of all.
Functionalism is the doctrine that a mental state is nothing but a functional state. Thus anything that so 'functions' as to translate sensory input into behavioural output is dignified with mentality. Under this doctrine computers would have mentality attributed to them if they could make stipulated input-output translations; and any further question of whether they actually 'saw', 'thought' or 'felt' anything is dismissed as irrelevant. Priest (1991) observes that functionalism "provides a philosophical framework within which to devise a scientific psychology without any need to address the ontology of a person." For example, pain is held to be not what is felt but what enables specific input-output transitions. The functionalist does not pause to ask whether pain could have the functional role it does unless it did actually hurt.
Instead of 'representing' the world or in any way thinking about it (or even making calculations or inferences about it) what computers do is to by-pass such processes while delivering what are for human purposes satisfactory input-output translations. A computer does not play chess; rather, it mimicks chess-playing. - If it did play chess, it would be appropriate to ask whether it enjoyed its game! (For a sustained refutation of the notion that computers or robots 'represent' or otherwise possess mentality, see Hacker (1990, Chapter I, 'Men, minds and machines').
The third realm of reality that was distinguished by Sir Karl Popper is that of 'human knowledge'. This realm might be said to bear the same relation to that of active mentality as does gc to gf.
The kow-towing to latter-day liberalism was a far cry from the efforts of Galton and Burt - intent as they had been on sweeping away those privileges and practices that could not be justified by the psychological facts. Eventually voters in California and Colorado would seize their chances in referenda to begin to reverse the tide; but many nation-states do not trust their electorates to vote on issues. Here the treachery of state-salaried experts in psychology would long prove crucial to maintaining Spanish practices - i.e. education and employment practices that were mere job-creation schemes for bureaucratic practitioners of White guilt and noblesse oblige.
In terms of respect for the human indilvidual, it would still be proper to allow children a choice of difficulty levels in their school work even if IQ did not turn out empirically to be the main guiding influence in children's own decisions.