Consequences of intelligence differences
”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.