NATURE, NURTURE, and NATURE via NURTURE
The debate about the relative importance of 'nature' and 'nurture' is the most important, the longest-running, and the most fraught of all those debates in psychology that occasionally appear resoluble. (The important and ongoing debate about how the mind is related to the body is almost as heated, but that debate usually appears entirely non-resoluble.
Until the proof, in 1945, of the scale of the Nazi Holocaust, belief in the importance of 'nature' had enjoyed a century of acceptance in the West. In the late nineteenth-century, traditional Christian approaches to improving people and society were unable to cope with the new problems of urban life-rising crime, conspicuous squalor, sexual diseases and child prostitution.
After the First World War, nation-states were increasingly expected by their enlarged electorates to do battle with their own social problems just as they had battled with each other militarily on an unprecedented scale, and to use science in peace as they had in war. Two particular strategies seemed possible. One was to control alcohol consumption by increased taxation or by outright prohibition. The other was to prevent the recurrence of similar social problems in future generations by introducing society's problem-cases to sterilization, castration, contraception or abortion -- if not to the sexual restraint long urged unavailingly by the churches. This second, futuristic route to 'improvement' presumed problems like mental subnormality {the 'learning difficulties' of today}, schizophrenia, criminality and alcoholism to be substantially inherited.
By 1945, it was clear for all to see that both these major efforts toward 'improvement' had been tried and had failed horrifically. In the USA, the 'prohibition era' had yielded more crime, alcoholism and drug-taking than before-together with a corruption of, and public mistrust for the police: laws restricting alcohol consumption had led to illicit brewing and retail, which in turn desensitized many moderate drinkers to engaging in crime.
In Nazi Germany, the initial proposals for 'race hygiene' via eugenics had been quickly discarded in favour of euthanasia for the mentally and physically handicapped and state-orchestrated terror for objectors in general and for the Jews in particular.
Finally, in 1941, as the armies of the Third Reich poured through Poland into Russia and the 'concentration' and slave-labour camps filled up, the Holocaust was set in motion. Now, quite regardless of health, educational attainment or IQ (the testing of which had been banned by Hitler in 1937, apparently to prevent the above-average IQ's of the Jews from being advertised), five million Jews, gypsies and homosexuals lost their lives to racial fanaticism.
After 1945, it became almost a matter of faith in psychology that important aspects of human personality, intelligence and rationality were mainly matters of 'nurture' rather than 'nature'; that 'improvements' were to be sought in education, training or psychotherapy, or by alterations in social conditions-especially for poorer families; and that psychology would follow the path outlined by Russian and American behaviourism.
However, by 1970, behaviourism -- with its stress on the importance of learning and on the apparent discovery of effective 'conditioning' procedures -- had itself taken some hard knocks in academic circles. These came partly from the growing recognition that 'conditioning' could not account for the phenomena of human language and symbol-using intelligence; partly from the increasing success of amelioration of mental illness by drugs; partly from failures of behaviour therapy to bite reliably on many 'unwanted habits' (especially on sexual fixations and on alcohol- and nicotine-consumption); and partly from direct empirical investigation of the role of 'nature' in human intellect, in personality differences, and even in social attitudes.
There are in fact three 'nature vs nurture' issues rather than just one. They concern what is innate, what is inherited, and what is important.
(i) What is innate to the species-in this case,
homo sapiens? What features of human behaviour and experience arise from the genes that we all share and without most of which a human child is unlikely to be born? Obvious possibilities are that language (or at least a certain capacity for language) is innate to Man; ditto bipedalism-conferring the major evolutionary advantage that we can carry things easily. But what about the sex-role division of labour -so general a feature of human cultures historically, but now under challenge?
Proving innateness (versus dependence on learning) of a largely species-specific characteristic-like birdsong - may seem easy enough: we 'simply' rear a bird without exposing it to conspecifics or their song. But we can hardly carry out the same experiment with human children today -though the feat was attempted by one or two rulers of the past (e.g. the Holy Roman Emperor Frederick II, who was curious to see whether children reared in isolation would end up speaking Hebrew, or whether the Almighty might have graced some other language with His approval).
Today there is much discussion of 'sociobiological' ideas as to how we evolved (perhaps as 'aquatic apes'?) and as to what is innate (altruism?, love of our own kith and kin?, inter-racial antipathy?); but to prove points decisively in either the 'nature' or 'nurture' direction is hard work; and such matters are so important that many people are properly reluctant to change their minds without decisive proof.
{The suggestion of the Nobel-Prize-winning German ethologist, Konrad Lorenz (1962,
Aggression: the So-called Evil), that human aggression is not only innate but actually 'desirable' (at least, intrinsic to distinctively human patterns of sociality) still remains the outstandingly controversial claim of ethology and sociobiology -- though Freud, too, thought we all had a 'death wish' of some kind that was normally channelled away from the self, towards external targets.}
Altogether, precise attributions of important, universal human features to 'either' nature or nurture looks quite unlikely. The incest taboo is an obvious example: it will be maintained 'naturally' in so far as societies are not so riven with internal strife as to put a premium on the special co-operation that will occur between the genetically similar offspring of incestuous unions; and it is also maintained by religious injunction and folk memory.
Again, the human sex-role division of labour has been well-nigh universal and thus a clear candidate to be thought 'innate'. Yet some obviously think this may change if females continue to have access to physical force (whether via the gun, labour-saving devices, or the police), can delay or abjure pregnancy and child-rearing, and can rely on their nation states to fund the education, health-care and even child-care of their own children while they themselves go out to work. {For presentation of modern nativist claims see e.g. M.Ridley, 1993,
The Red Queen and M.S.Gazzaniga, 1994,
Nature's Mind.}
(ii) Which differences between us are inherited genetically from our parents? Which characters 'breed true'-with people being more similar to each other according our estimates of the number of genes they share? With which traits can it be said that a 'eugenics' programme would be likely to have some degree of at least technical success? With this matter there are three obvious main lines of systematic inquiry.
(a) We can look at genetically similar (or even identical people (monozygotic (MZ) twins)) who grow up in different environments, thus allowing us to learn whether environmental differences, between families, contribute to final observable ('phenotypic') differences in behaviour and personality.
(b) We can look at children who are genetically unrelated (by population standards) and who grow up in the same family environment-as when adoptive children grow up alongside genetically unrelated children of similar age.
(c) We can look at pairs of children who share the same environment, but who differ in their degree of genetic similarity-as do MZ and DZ (dizygotic, 'fraternal') twins. We ask whether, with environment similar for the twins making up each pair, the greater within-pair genetic similarity (of the MZ's) makes for greater within-pair phenotypic similarity {as measured by intra-class correlation coefficient}.
Of course there are variants on all these methods. For example, in the 1990's there are many half-siblings who grow up largely apart, for example. More importantly, each method has its own limitations. Adoptive children may have been selected by agencies in the past as especially 'suited' to the families to which they were assigned: thus a brown-eyed child might not be assigned to blue-eyed adoptive parents, and a child of a well educated biological mother might be sent to a relatively bookish home.
Investigators have tried variously to allow for, circumvent or neglect such methodological problems. In particular, careful attention is essential to the genotypic, phenotypic and environmental ranges across which any particular study has been conducted: relatively few adoptees are adopted into the extremes of the range of human environments, for example; and twin studies using volunteers will usually under-represent pairs carrying genes for relatively low levels of IQ
In recent years there has been an enormous increase in high-quality psychogenetic work in many Western countries. Interpretations remain contested in some quarters (e.g. L.J.Kamin, 1984,
Science; C.R.Brand, 1987,
Nature); but a certain amount of fresh practical advice on child-rearing and education can be offered on the basis of the emerging research picture (Brand, 1989, in D.Anderson,
Full Circle).
(iii) How do people come to differ as much as they do? How does phenotypic population variance arise? Is it largely accounted by 'broadly heritable', or genetic factors? Importantly, this question is different from the last two, for not all genetic variance is inherited. The best known example of this is the case of eye-colour in
homo sapiens: two brown-eyed parents can have a blue-eyed child if each of them carries the 'recessive' gene for blue eyes as well as the 'dominant' gene for brown eyes.
Interaction between genetic factors (
epistasis) is another purely genetic phenomenon that will not make for marked parent-child or sibling-sibling similarity: if a certain combination of genes is crucial to a character, within-family resemblances will be modest, since genes segregate in the process of transmission. Tracing such minimally transmissible effects is much harder; and, when they are found, they may somewhat upset the interpretation of other studies: for example, outstanding phenotypic similarity in MZ twin-pairs may reflect
epistasis as much as 'narrowly heritable' genetic variance.
Lastly, we come to entirely non-transmissible genetic effects -as when genes mutate or when chromosomes are damaged or appear in triplicate. (For example: 'Fragile X' and 'Down's syndrome' are often the causes of mental retardation in children from families having no general propensity to produce lower-IQ children).
The way ahead to the identification of further such genetic effects is highly technical and even then serendipitous; but at present it is widely believed by geneticists (and by some people who are anxious about the prospect of a 'new eugenics') that many further gene-phenotype links will be discovered as the human genome is mapped in its entirety (see e.g. D.J.KEVLES and L.HOOD, 1992,
The Code of Codes, Harvard University Press).
It would be nice to be able to say that whatever features of personality, intellect, psychopathology etc. cannot be attributed to genetic features must clearly be put down to 'the environment', and vice versa. However, psychologists long ago decided that matters were not so simple, and modern work provides ways of firming up this hunch.
Initially, saying that 'nature and nurture interact' -- perhaps 'inextricably' -- to yield human outcomes did little more than draw a veil over the failure of environmentalist theories to prove their main case. To talk of genetic-environmental interaction was more to obfuscate than to clarify. Strictly speaking, G x E interaction occurs when an environmental difference multiplies with a genetic value in determining phenotypic outcome: for example, a good violin level attained by a child will probably reflect not just 'genes for musical ability' and 'a good violin teacher', but their interaction or multiplication-there will probably be little attainment to show for having one but not the other.
Is such G x E interaction a powerful influence in human affairs? Well, if there is a lot of it around, it should mean that MZ twins will be especially similar only when they grow up in similar environments: and this phenomenon is not readily apparent across the range of psychometric test-score 'phenotypes'. However, many other things have been alluded to under the heading of 'interaction effects' by non-specialists; and the most compelling of these is the idea that a child's development occurs as it 'interacts with the environment'.
Since virtually all children quite literally 'interact with the environment' (with the important exception of grossly handicapped children), it is not immediately obvious how this observation is supposed to enable us to account for eventual differences between children. But in recent years, several techniques have come on stream for identifying various forms of what is properly called genetic-environmental covariation (G,E COV).
Theoretically there are three types of G,E COV that may help produce full population variance:
(1) Genotype and environment may be correlated by certain types of children being born into certain types of environment-as with children having genes for high-IQ [if there are such genes, of course] being born into environments that are themselves [correctly] judged by modern educators and social workers to be more likely to boost development.
(2) Parents, educators, etc., may decide to supply a certain type of environment to a certain type of child-smiles for a pretty girl, punishment for a cheeky boy, violins for children who seem interested and prove themselves capable, etc.
(3) Lastly, the genotype itself may lead its possessor to active selection of particular environment-as the child itself comes of an age to choose its toys, treats, friends, hobbies, school subjects etc.
These last two types of G,E COV can usefully be called 'transaction' with the environment: the point is that G has yielded, passively or actively, a changed environment (whether by selection or creation) that, in its turn, will normally be expected to influence the child further. If such 'transactions' occur, perhaps especially of type (iii), then we could expect that children will diverge as they grow up unless they are genetically identical.
And this is just what has seemed to happen in the few studies that have looked for the effect: at around seven years, DZ twins are almost as similar as MZ twins; but by adolescence the DZ's have diverged while the MZ twins have remained as similar as they were. What seems to happen is that the environment is not, as behaviourists could make it for their laboratory animals, a truly independent variable operating from outwith the 'organism'. Quite the contrary: environmental differences between us are largely under our own control after childhood, and psychological divergence seems to follow in line with genetic differences that may not have expressed themselves at all until such environmental opportunities arise.
Classical environmentalists would wish us all exposed to a limited diet of systematically improving arrangements. They would perhaps wish all children to be exposed to the standard British primary 'school' with its staff trained in sociology and Piagetianism. By contrast, the 'transactionist' will look especially at whether the environment provides variety and choice for children, and at whether the environment is responsive to the highly individual pressures from growing children for intellectual and emotional development beyond the levels that individual children have already reached.
Such are some of the main arguments, methods and types of finding that are brought to bear on 'nature-and-nurture' issues today. In general, enormous progress in the direction of agreement amongst experts has occurred in recent years, with few simple social-environmentalist claims being left on the table-except those concerning extreme environments that are seldom encountered in the West.
This would once have seemed a pessimistic thing to say; but it is no longer so. With years of slight achievement for social-environmentalist techniques behind us and with gene replacement therapy said to be just around the corner, probably the happiest thing that victims of psychological ill health or 'learning difficulties' could be told would be that their grandchildren, at least, would be spared their condition.
Whether people will be any more responsible about the 'new eugenics' than the old will remain to be seen. It is always possible that powerful new environmental variables-not seen so far in the twentieth century -will come into play and yield variance between people that would quite dwarf the human differences that result perhaps mainly from genetic differences today. Such overwhelmingly powerful environmental features would presumably resemble those associated historically with religion and associated pressures for strict socialization -- an environmental pressure for which the twentieth-century West professed little use.
More likely, increasing provision of equal opportunity and choice-now available to children in their own homes thanks to the proliferation of TV channels-will mean that the intellectual and personality differences that remain in future populations will be increasingly of genetic origin. High heritabilities will thus be a major testimony to the achievement of equal opportunities for all.
For quotes in support of the above summary see
here.
------------------------------------
Comments?
Email Chris Brand.
Some history.
-----------------------------------
