We conclude that there are no overall (average) differences between women and men in general intelligence, but there are some large and persistent differences on cognitive abilities that on average favor males (e.g. mathematics, mental rotation, mechanical) or favor females (verbal ability, most tests of memory). There are more males in the low end of the intelligence distribution, at least in part, for sex-related genetic reasons. There is no genetic evidence for more males in the high end of the intelligence distribution. Paradoxically, societies with greater gender equality do not show reduced differences on many cognitive measures. Our conclusions are about group differences. Thus, these mean differences have no clinical or social significance at the individual level.

There are large between-country differences in measures of economic and noneconomic well-being. Many researchers view increasing the stock of human capital as the key to raising economic development, promoting democratization, and improving health, and hence improving overall societal well-being. The single most studied aspect of human capital concerns cognitive competence. Differences in population cognitive competence might explain these societal differences. Evidence suggests that education builds cognitive competence, and education and cognitive competence promote better social outcomes, in terms of both economic and noneconomic factors. However, measuring population cognitive competence for countries requires representative samples, culture-fair tests, equivalency in the relationship between test measures and other cognitive attributes, and comparability in testing situations. In most cases, none of this has been achieved.

This chapter describes and discusses causes for national and historical differences in cognitive ability, covering wealth, health, politics, modernity, education, geography and climate, evolutionary-genetic dispositions and finally culture, including worldviews and religion. It analyses direct and indirect, reverse (of ability) and reciprocal effects. Cognitive ability depends on the described factors but also amplifies their effects and shapes them.

Methods and peculiarities of cross-country human capital research are described, and solutions for problems are offered: in general, a scientific approach guided by epistemic rationality is suggested; more specifically, measurement and comparability problems are discussed; causality, correlation and path analysis; relations between individuals and categories at different levels (including ecological fallacy and conclusions from groups to individuals and from individuals to groups).

After summarising the results and comparing them with the major insights of other researchers, strategies of intervention for improving the development of cognitive human capital and the wellbeing of nations are presented. Mentioned are health policies; within and outside family educational policies; cognitive training; demographic and migration policies; institutional and political reforms and the development of culture.

The concepts of human capital, cognitive ability and intelligence are introduced. We compare different ways to measure them. Development, causes for development and for differences, and furtherance approaches are outlined.

The cognitive ability level of intellectual classes, frequently termed ‘elites’, is crucial for technological development and more generally for the governance, maintenance, wellbeing and development of a society.

For several decades, research has documented large differences in the results of cognitive ability tests – large differences between generations and between countries. Whether these differences reflect real cognitive ability differences is still a contentious issue. We document the results and give evidence for an interpretation of them as real world differences: they are backed by further statistical indicators of cognitive achievement and by comparisons with everyday life experiences in different regions of the world.

Large income and wealth differences across time and between nations are described. We start by presenting economic production and income measures indicating wealth. We will finish by showing limitations and possibilities for improvement.

In this chapter models will be tested which combine background and specific factors and their interdependence. The models examine whether there is evidence for culture-education and evolution-education theories that explain cross-country differences in cognitive human capital leading to patterns in institutional quality, economic freedom, production and income finally resulting in differences in wealth, politics and wellbeing.

The broad field of culture will be defined and structured. Worldview is the core of culture. Culture has a strong impact on the development of economy and politics and especially on education and competence. The central concept of ‘burgher-civic’ culture and its influence on societal wellbeing will be described. Finally, modernisation is understood as the result of reciprocal effects between culture, education, competence, society, institutions and economy best visualised as a spiral.

The wellbeing of nations comprises more than just economic wealth. It includes health, environmental, psychological, social, political and cultural attributes of societies. National development is given a normative frame – what is good and what is aimed at.