A new book debunks 35 commonly-held myths about intelligence, IQ, and heritability:
In the spirit of correcting misapprehensions quickly, here are some snap answers to the first 6 questions:
- In fact, when the same people are given very different intelligence tests, including tests constructed in the belief that there is no general factor, the general factors extracted from the disparate tests correlate at above the .9 level.
- Mental tasks correlate with each other, and it is easy to extract a general factor (and also some group factors) so it is not unwarranted to summarize people’s general level of ability with one number.
- Brain size is weakly related .2 to .4 with intelligence, frontal lobes probably in the higher part of that range. Brighter people have more neurons in their brains, and those neurons are more densely packed together and, perhaps counter-intuitively, have fewer connections branching off each neurone. So, intelligence does have a relation to brain function, but research is at an early stage.
- If intelligence really varies in character between different cultures, then it should be very difficult to extract the “Western” general factor, yet in 31 countries, and using a wide variety of tests, 94 of the 97 (96.9{5c1a0fb425e4d1363f644252322efd648e1c42835b2836cd8f67071ddd0ad0e3}) samples produced g either immediately or after a second factor analysis. Moreover, the g factor is about as strong in the non-Western samples as it is in typical Western samples. Most countries find “Western” intelligence tests very useful, once they have been translated and some language and specific knowledge items altered or removed. To cap it all, dogs, rats, mice, donkey and primates show g factors. It looks like an evolutionary adaptation.
- Everyone seems to want multiple intelligences, particularly educationalists. However, even when researchers attempt to measure these multiple intelligences, the result is a series of correlated variables that produce a general factor, which is exactly what should never occur, according to the theory. Moreover, the proposer of the theory did not think it necessary to make it testable.
- If practical intelligence could be measured, American Football teams would find it extremely useful. Instead, they use the Wonderlic intelligence test, because it correlates with some of the more complicated playing abilities. The proposer of the theory does not specify what results will prove that practical intelligence differs from general intelligence.
It’s true that IQ is an imperfect proxy for whatever multiplicity of genes happens to produce the observable differences in what we generally call intelligence. But even given the limited current state of scientage on the subject, what would have to be denied in order to completely reject intelligence and IQ, as well as their heritability, would also require the abandonment of virtually everything we believe we know on a statistical basis, as well as a considerable portion of the entire scientific knowledge base.
This is why I don’t pay much attention to IQ critics, even when they happen to be legitimately brilliant men who are otherwise well worth listening to. While their criticisms of this or that particular may be relevant, they don’t even begin to shake the foundations of what has been reliably observed to be true as well as solidly supported by scientody.