The Heritability of Intelligence: Not What You Think

Scientific American:

One of the longest standing assumptions about the nature of human intelligence has just been seriously challenged.

According to the traditional “investment” theory, intelligence can be classified into two main categories: fluid and crystallized. Differences in fluid intelligence are thought to reflect novel, on-the-spot reasoning, whereas differences in crystallized intelligence are thought to reflect previously acquired knowledge and skills. According to this theory, crystallized intelligence develops through the investment of fluid intelligence in a particular body of knowledge.

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In a new study, Kees-Jan Kan and colleagues analyzed the results of 23 independent twin studies conducted with representative samples, yielding a total sample of 7,852 people. They investigated how heritability coefficients vary across specific cognitive abilities. Importantly, they assessed the “Cultural load” of various cognitive abilities by taking the average percentage of test items that were adjusted when the test was adapted for use in 13 different countries.

Read the whole story: Scientific American