IQ and Global Inequality

Summary

In IQ and Global Inequality Lynn and Vanhanen argue that intelligence, as measured by IQ tests, is a major contributor to national wealth as well as to various measures of social well-being. They base this argument on the finding that nations' average IQs have a strong correlation with several such factors, among them adult literacy (0.64), tertiary education (0.75), life expectancy (0.77), and democratization (0.57). The book is a follow-up to Lynn and Vanhanen's 2002 book IQ and the Wealth of Nations, and expands on many of the ideas presented in their earlier book.

IQ and Global Inequality responds to some of the criticisms directed against the earlier book. To address the criticism that measures of national IQ are unreliable, for 71 nations they measure national IQs using two different methods, and find that the correlation between different measures of national IQ is 0.95. As a further argument for reliability, they find that their reported national IQs are correlated with various measures of math and science achievement, with correlations ranging from 0.79 to 0.89.

Finally, the book presents the authors' theory as to the cause of national IQs. They propose a model of gene-environment interaction in which high IQ leads to better nutrition, education and health care, further enhancing IQ. They also propose that the racial composition of countries is an important factor in national IQs. They base this conclusion on the observation that national IQs can generally be predicted from the countries' racial composition, and that national IQs of racially similar countries tend to cluster together.

National IQ and QHC values

Lynn and Vanhanen base their analysis on selected IQ data from studies which covered 113 nations. For another 79 nations, they estimated the mean IQs on the basis of the arithmetic means of the measured IQs of neighboring countries. They justify this method of estimation by claiming that the correlation between the estimated national IQs they reported in IQ and the Wealth of Nations and the measured national IQs since obtained is very high (0.91).

Lynn and Vanhanen calculated the national IQs in relation to a British mean of 100, with a standard deviation of 15. They adjusted all test results to account for the Flynn effect: adjustments were 2 points per decade for Raven's Progressive Matrices and 3 points per decade for all other types of tests. When two IQ studies were used from one country, their mean was calculated, whereas when three or more were available, the median was used.

Reception

The book received a mixed reception with most academics criticizing both the methodology and conclusions.

In a review J. Philippe Rushton, President of the Pioneer fund that has been a long time funder of research by Lynn, writes that the book extends and answers criticisms against the earlier work in several ways. Rushton concludes that the methods is accurate. Rushton states that the national IQs have very high validity as measures of national differences in cognitive ability. He states that "They show that there is remarkable consistency in the IQs of nations when these are classified into racial clusters."

In contrast to Lynn, Kanazawa "contends that it is the evolutionary novelty of the environment which increased general intelligence" and not the cold climate and harsh winters as Lynn states.

The methods of the study were criticized by Richard E. Nisbett for relying on small and haphazard samples and for ignoring data that did not support the conclusions.

In an article published in European Journal of Personality, Heiner Rindermann compared the IQ scores from the book to a large number of international student assessment studies on subjects such as reading, mathematics, science, and problem solving, and found them to be highly intercorrelated. Statistical analyses indicated that the results could be explained by an underlying general cognitive ability. More than 30 commentaries on Rindermann's findings were published in the same issue of the journal.

The study A systematic literature review of the average IQ of sub-Saharan Africans by Jelte M. Wicherts and colleagues stated that:

However, the study also did its own literature review on the average IQ of sub-Saharan Africans. It did not find as low a value as the book, below 70, but the estimated average value of 82 is still low compared to industrialized nations. Regarding four studies comparing and finding agreement between Lynn's estimated national IQs and the international student assessment tests, they disagree regarding sub-Saharan Africa but write "these four studies appear to validate national IQs in other parts of the world."

Richard Lynn and Gerhard Meisenberg in turn replied that "critical evaluation of the studies presented by WDM shows that many of these are based on unrepresentative elite samples" and that a further literature review, including taking into account results in mathematics, science, and reading, gave "an IQ of 68 as the best reading of the IQ in sub-Saharan Africa". Wicherts and colleagues in yet another reply stated: "In light of all the available IQ data of over 37,000 African testtakers, only the use of unsystematic methods to exclude the vast majority of data could result in a mean IQ close to 70. On the basis of sound methods, the average IQ remains close to 80. Although this mean IQ is clearly lower than 100, we view it as unsurprising in light of the potential of the Flynn Effect in Africa (Wicherts, Borsboom, & Dolan, 2010) and common psychometric problems associated with the use of western IQ tests among Africans."

Consequently, some later studies using average national IQ data have checked their results against both data sets.

Jones and Schneider commenting on the differences to the earlier book write "LV (2002) assembled results from 183 conventional IQ tests, both verbal and visual, given in 81 countries across the entire 20th century;they used hundreds of IQ tests from 113 countries across centuries in LV (2006). They aggregated these results using best practice methods to create estimates of “national average IQ” for these countries. LV show in those works as well as in Lynn (2006) that the IQ gaps between regions of the world have not appreciably changed during the 20th century."

Earl Hunt cited Lynn and Vanhanen's work as an example of scientists going far beyond the empirical support to make controversial policy recommendations, and as such as examples of irresponsible uses of science. Hunt argues that in their argumentation they both made the basic mistake of assigning causality to a correlation without evidence, and that they made "staggeringly low" estimates of Sub-Saharan African IQs based on highly problematic data. He considers that by their negligence of observing good scientific practice Lynn and Vanhanen are not living up to the basic responsibility of scientists to make sure that their results can function as reasonable empirical support for policy decisions.