IQ and the health of nations: some critical comments on Kanazawa (2006)

Cognitive epidemiology aims to explain health differentials in terms of cognitive functions, including intelligence. Kanazawa has proposed extending this to the explanation of health differences between nations. He concludes that 'wealthier and more egalitarian societies live longer and stay healthier ... because they are more intelligent'. The result does not apply to sub-Saharan Africa, but this exception is explained by reference to his theory of evolutionary psychology, 'The Savanna Principle'. We reanalyse the data, taking into account non-linearity in the relationship of GDP to life expectancy and find that the results no longer support his conclusions. We also argue that HIV prevalence rates are a more parsimonious explanation for differences between sub-Saharan Africa and elsewhere.