The economic historian Richard Wilkinson has argued that economic inequality leads to shorter life expectancy because being at the bottom of the social pile puts people under prolonged stress. But Kanazawa rejects this hypothesis. He argues his data show that once population IQ is taken into account, a country’s average life expectancy is no longer related to economic development and inequality. Indeed, he found IQ was between seven and eight times more strongly related to life-expectancy than were measures of income inequality.
Kanazawa’s theory is that what we refer to as IQ is effectively a measure of people’s ability to adapt to evolutionarily new threats and demands. Populations with a higher IQ are, he argues, better able to deal with contemporary hazards like guns, cars, sedentary lifestyles (by having the sense to exercise), and drugs and alcohol – thus living longer. And he rejects the notion that IQ is simply an indirect measure of economic wealth via improved education. Intelligence, he argues, is largely genetically determined.
To support his case further, Kanazawa also focused on 29 sub-Saharan countries which have changed little since ancient times. In these countries where modern threats are absent, Kanazawa found IQ is not related to life-expectancy whereas income inequality is.
Kanazawa’s findings come after a recent Scottish study reported a positive association between intelligence and longevity, and another study that found less obese men were more intelligent than their obese peers.
“These results point to the need for epidemiologists and health psychologists to pay closer attention to the role of general intelligence in health and longevity. General intelligence may be the key that allows individuals in evolutionarily novel contemporary society to recognise health risks and deal with them appropriately”, he concluded.
Kanazawa, S. (2006). Mind the gap…in intelligence: Re-examining the relationship between inequality and health. British Journal of Health Psychology, 11, 623-642.
Link to related review paper.
Link to the IQ data used by Kanazawa.
Update: After reading this Digest item, Observer journalist Denis Campbell has investigated further.
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