Literacy not intelligence moderates the relationships between economic development, income inequality and health

Abstract:Objectives. Kanazawa (2006) presented data allegedly supporting a racist version of evolutionary psychology that claims that the populations of wealthier and more egalitarian societies live longer and stay healthier, not because they are wealthier and more egalitarian, but because they are more intelligent. The objectives of this study are: (i) to determine the relationship between IQ and literacy in Kanazawa's sample of countries and (ii) to reanalyse Kanazawa's dataset using measures of literacy in lieu of national IQ test scores.

Method. Correlation and regression were employed.
Results. National literacy scores across the countries in the sample are highly skewed. In spite of this, the literacy measures are highly correlated with alleged differences in national IQ (r = .83-.86). The measure of literacy together with economic development (GDPpc) and income inequality (Gini coefficient) control at least 59-64% of the variance in national life expectancy at birth.

Conclusions. There is no scientific justification for believing that alleged intelligence differences play any role in explaining international differences in health status. Measures of alleged national IQ scores are highly confounded with differences in literacy. Literacy is a key factor in the health of any community and policies designed to enhance the literacy of a population are expected to lead to significant improvements in health status.

Marks (2007)


The Kanazawa paper 'IQ and the wealth of states' and his paper Mind the gapin intelligence: Re-examining the relationship between inequality and health have been criticised in several papers:

Dickins et al. (2007)

Kanazawa (2006) has put forward an evolutionarily grounded theory which claims that individuals in wealthier and more egalitarian societies live longer and stay healthier not because they are wealthier or more egalitarian but because they are more intelligent (2006: 637). The claim rests on an argument which asserts that general intelligence is a solution to evolutionarily novel problems and that most dangers to health in contemporary society are evolutionarily novel. Kanazawa also claims that this relationship does not hold in sub-Saharan Africa. These claims are based on a cross-national analysis which finds a positive correlation between 'national' IQ scores and mortality data. The implication is that intelligence is the principal factor determining longevity in the rest of the world, regardless of issues such as adequacy of diet and availability of health care. Kanazawa's theoretical claims about the evolution of general intelligence as a domain-specific adaptation are inconsistent with adaptationist analysis: natural selection does not solve general problems. The assumptions that sub-Saharan Africa is more representative of the evolutionary past than is the rest of the world, and that most hazards to health in contemporary society are evolutionarily novel, are implausible. The methods used are inadequate because Kanazawa argues for causation from correlation and fails to consider alternative explanations. The IQ data are flawed for reasons to do with sample size and sampling, extrapolation and inconsistency across measures. Nor are they temporally compatible with the economic and demographic data

From Geoff (2007)
Kanazawa 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.