Consequences of intelligence differences
Education
”People who score better on intelligence tests tend to stay longer in education, to gain higher-level qualifications, and to perform better on assessments of academic achievement. Some of the correlations between intelligence scores at the end of primary school and academic results some years later are high, suggesting that it is not just a matter of education boosting intelligence. Also, educational attainment has a moderately high heritability, and a strong genetic correlation with intelligence. On the other hand, there is also evidence that education can provide a boost to
scores on tests of complex thinking, and some of these increments last into
old age. Therefore, there is probably a bidirectional causal association between intelligence and education.”
Social status and mobility
“People who score better on intelligence tests tend to go into more professional occupations (typically those with higher status) and to perform better
in the workplace. There is a positive association between intelligence test
scores in childhood and social position later in life: people who score higher
tend to be in more professional jobs, to live in less deprived areas, and to
have higher incomes.” By the way, this is not due to people publishing their intelligence test results in their job applications nor, usually, to employers conducting their own intelligence tests (though that would often be useful). These results are obtained by looking at historical intelligence test results years after the children have grown up and finished their professional careers.
“The association is not perfect. Results show that, when it comes to attained social position in maturity, intelligence, education and parental background all count to
some extent. That is, there is some meritocracy and intelligence-driven social mobility, and there is also some social inertia.”
Intelligence seems to have a cumulative effect, and relates more strongly to occupational and social position later rather than earlier in adulthood. Even bright kids join rock bands for a while. Some do it part time for ever. http://www.dancingmice.co.uk/
Intelligence and health
Intelligence is associated with better health and longer lifespans, but it is not entirely clear why. The early explanation was that more intelligent people learned quickly how to avoid health hazards. The gave up smoking sooner in life, bothered to read the medicine labels, and followed health advice generally. Now it seems possible that both intelligence tests and life itself test a general underlying bodily system integrity, a fundamental mens sana in corpore sana which, if you are lucky enough to have it, gives you health, intelligence and long life without much exertion on your part. Typical, isn’t it, that evolution doesn’t understand human concepts of fairness and equity? Also typical that many very good papers were written showing how intelligent people avoided health hazards, and now it turns out that those will have to be re-written.
Age related cognitive decline
Please read this section slowly, and with great care, because you may be asked questions about it later.
“There are declines in cognitive function even among people who do not develop dementia. Not all cognitive functions decline at the same rate. Some cognitive functions — often referred to as markers of crystallized intelligence — hold up well with age. These include vocabulary and general and specific knowledge. The cognitive
functions that tend to decline are called fluid intelligence. These tend to involve on-the-spot thinking with novel materials, and in situations in which past knowledge is of limited help. This includes abstract reasoning, spatial abilities, processing speed, and working and other types of memory.
Not everyone experiences the same rate of cognitive decline, and there is a growing interest in the genetic and environmental (biological and social) determinants of people’s differences in age-related cognitive changes. Some of the more solid
evidence exists for the following being cognitively protective: not having the
APOE e4 allele, being physically more active and fit, and not smoking.”
Two main hypotheses are: some people have a “cognitive reserve” such that their brains are better able to withstand damage, perhaps because a bigger brain provides redundancy or because some people’s brains are more flexible in reorganizing networks to regain or retain cognitive functions; or the common system hypothesis that age-related decline of different bodily systems is correlated; that people who are experiencing faster cognitive declines might also be experiencing faster declines in sensory and some physical functions, making researchers consider inflammation,
oxidative stress, telomere length, and the hypothalamic-pituitary-adrenal axis as common causes of variance.
"Now it seems possible that both intelligence tests and life itself test a general underlying bodily system integrity, a fundamental mens sana in corpore sana which, if you are lucky enough to have it, gives you health, intelligence and long life without much exertion on your part. Typical, isn’t it, that evolution doesn’t understand human concepts of fairness and equity? Also typical that many very good papers were written showing how intelligent people avoided health hazards, and now it turns out that those will have to be re-written."
ReplyDeleteThank you for that!
You have no idea how hard it is to get that point across even within our "community". Well, to be more accurate, not just that idea, but its implications. Even within the IQ-realist sphere, there is a very "environmentalist" view on health. Where health is concerned, people believe – without necessarily much empirical basis – that nurture (or, at least, how one "nurtures" oneself) trumps nature. The evidence we have isn't being kind to that view. Most major chronic diseases show a strong a strong hereditary component – or are (as in the case of many/most cancers) – completely erratic, show low heritability and no connection to IQ. Many of the latter ailements have been shown to be linked to infections. In either case, "nurture" – or what one does with oneself, may play far less of a role than we think.
Most people can't seem to see that most of ideas on health are flawed – not only for the reason that most of them are is based on minimally useful observational studies – but because we fail to take the relationship between IQ and intrinsic health into account. The sad part is that this is fairly easy to remedy: we could compare health outcomes when controlling for IQ. Whatever factors we find that predict health and longevity more strongly than IQ would definitely warrant closer investigation.
Readers can see more at:
IQ and Death | JayMan's Blog
Thanks very much for your observations, and for the link. Revolutions in thinking are always hard, and medicine tends to be slow to adjust to new findings because medical students are put under such pressure to pass exams that they tend to treasure what they learned during their training above all else. Also, they are punished for new mistakes, but forgiven for most outcomes that follow normal practice and protocols. Not always a bad thing, but it slows the pace of innovation. As you observe, we are going to have to make it a standard procedure to control for IQ in our risk estimates. Finally, we are doing the obesity experiment anyway, so we will have good data on its effects in about 40 year's time.
Delete"we could compare health outcomes when controlling for IQ". YES! This should be standard practice. IRBs and studies need to have recontact information to be able to get it though. Possible to try and pass laws to allow grabbing this information from national databases if available for medical research?
ReplyDeleteHey, we are just researchers! Don't get the lawyers involved. If people want to help, that's great. If they want to give us a wide berth, suspicious about what use we might make of their data, that their call. Anyway, please let me know all your scores on all the tests we fool around with here. Will be posting another online test site tomorrow.
ReplyDeleteA great deal of what looks like age-related decline to naive studies is actually the Flynn Effect -- give the old folks the same sort of tests they took when they were young and most of the decline goes away.
ReplyDelete