Michael Muthukrishna

“Here are ten facts about IQ. These facts are debated and often controversial among the general public but far less so among scientists who
study intelligence. The best review of the academic literature
supporting these facts is a 2012 paper by Richard Nisbett and
colleagues – an interdisciplinary team of leading scholars, household
names within intelligence research, comprised of psychologists, an
economist, a behavioral geneticist, and a former President of the
American Psychological Association. Their areas of expertise include
cultural and sex differences in intelligence, the effect of social and
genetic factors that affect intelligence, the development of intelligence
over the lifespan, the relationship between economic development
and intelligence, and changes in intelligence over history

1. IQ is a good predictor of school and work performance, at least in WEIRD societies.

2. IQ differs in predictive power and is the least predictive of performance on tasks that demand low cognitive skill.

3. IQ may be separable into what can be called ‘crystallized intelligence’ and ‘fluid intelligence’. Crystalized intelligence refers to knowledge that is drawn on to solve problems. Fluid intelligence refers to an ability to solve novel problems and to learn.

4. Educational interventions can improve aspects of IQ, including fluid intelligence, which is affected by interventions such as memory training. Many of these results don’t seem to last long, although there is strong evidence that education as a whole causally raises IQ over a lifetime.

5. IQ test scores have been dramatically increasing over time. This is called the Flynn effect after James Flynn (also an author of the review mentioned above), who first noticed this pattern. The Flynn effect is largest for nations that have recently modernized. Large gains have been measured on the Raven’s test, a test that has been argued to be the most ‘culture-free’ and a good measure of fluid intelligence. That is, it’s not just driven by people learning more words or getting better at adding and subtracting.

6. IQ differences have neural correlates – i.e. you can measure these differences in the brain.

7. IQ is heritable, though the exact heritability differs by population, typically ranging from around 30% to 80%.

8. Heritability is lower for poorer people in the US, but not in Australia and Europe where it is roughly the same across levels of wealth.

9. Males and females differ in IQ performance in terms of variance and in the means of different subscales.

10. Populations and ethnicities differ on IQ performance.

You can imagine why some people might question these statements. But setting aside political considerations, how do we scientifically make sense of this?

Popular books from Richard Herrnstein and Charles Murray’s The Bell Curve (1994) to Robert Plomin’s Blueprint (2018) have attributed much of this to genes. People and perhaps groups differ in genes, making some brighter than others. But humans are a species with two lines of inheritance. They have not just genetic hardware but also cultural software. And it is primarily by culture rather than genes that we became the most dominant species on earth. For a species so dependent on accumulated knowledge, not only is the idea of a culture-free intelligence test meaningless, so too is the idea of culture free intelligence.”
― Michael Muthukrishna

“Cooperation requires finding ways to suppress that selfish urge. If your policy is to rely on goodwill alone then it's a bad policy, because between selfishness and altruism, all else being equal, selfishness wins in the end. Taking advantage of others is an easier and more efficient way to gain more resources.”
― Michael Muthukrishna, A Theory of Everyone: The New Science of Who We Are, How We Got Here, and Where We’re Going