October 18, 2013

Dominant view of intelligence falsified

Scott Barry Kaufman writes in Scientific American that a dominant view by psychologists of intelligence has been seriously challenged by research by Kees-Jan Kan (photo) and his colleagues. According to this dominant view the heritability of crystallized intelligence (≈ acquired knowledge) is expected to be lower than the heritability of fluid intelligence (≈ 'raw' intellectual ability). Kan et al's research, however, has shown that this is not the case. First, they determined the cultural load of intelligence test which is the degree to which tests had to be adjusted for it to be used in different countries. They found that the cultural load of tests was correlated positively both with 1) general intelligence (the g-factor) and with 2) the heritability of the test.

"The researchers argue that their findings are best understood in terms of genotype-environment covariance, in which cognitive abilities and knowledge dynamically feed off each other. Those with a proclivity to engage in cognitive complexity will tend to seek out intellectually demanding environments. As they develop higher levels of cognitive ability, they will also tend to achieve relatively higher levels of knowledge. More knowledge will make it more likely that they will eventually end up in more cognitively demanding environments, which will facilitate the development of an even wider range of knowledge and skills."
Interestingly, this work is also relevant for understanding the gap between IQ scores between ethnic groups. Psychologist Arthur Jensen and others thought that this gap was genetically caused. But this new research suggests the opposite: the larger the gap, the more it is determined by cultural influences.

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