July 16, 2006

IQ and Intelligence

Two “consensus” definitions of intelligence:
"Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings—“catching on,” “making sense” of things, or “figuring out” what to do."
Gottfredson (1997)

"Individuals differ from one another in their ability to understand complex ideas, to adapt effectively to the environment, to learn from experience, to engage in various forms of reasoning, to overcome obstacles by taking thought. Although these individual differences can be substantial, they are never entirely consistent: A given person’s intellectual performance will vary on different occasions, in different domains, as judged by different criteria. Concepts of “intelligence” are attempts to clarify and organize this complex set of phenomena."
Neisser, et al. (1996)

IQ is not simply a measure of intelligence, it is the most accurate (i.e. reliable and valid) of all psychological tests and assessments at predicting the performance of simple tasks, academic success, job performance, health, longevity, functional literacy, socioeconomic advancement, “social pathologies” and brain size.

The differences are partly genetic and partly environmental. The evidence suggests that 50%-80% of the group differences in average IQ is genetic. The heritability of IQ changes with age: in childhood it is about 0.45; by late adolescence it is around 0.75. The rest is due to the environment.

IQ was normalized to obtain a mean scores of 100 using UK data, but varies globally; the average human IQ is presently 88.8.
Africa (excluding Northern Africa): 68.6
Eastern Asia (excluding China): 105.2
Southern Asia: 81.0
Europe: 98.6

The understanding and acceptance of the fact that intelligence is largely genetic has social and policy implications. Most importantly, significant differences in the intelligence of different individuals brought up in a similar environment are natural and to be expected. Therefore, accusations of laziness on the part of an individual, blame on the part of the parents or moral culpability on the part of the state are all unwarranted.

Posted by Martin Sewell at July 16, 2006 12:31 AM | TrackBack