A long-term increase in the fluid intelligence of English children.

In the early decades of the century a number of geneticists and psychologists believed that intelligence in the economically advanced nations was in secular decline. Contrary to this expectation, recent data for a number of countries have shown that intelligence has been increasing at rates far greater than hitherto considered probable. A compilation of this data by Flynn for 14 economically advanced nations has shown that intelligence quotient (IQ) rises have generally been within the range of 2-12 IQ points per decade. These recent studies raise several questions, among which are precisely what abilities have been increasing over time; and whether existing data are correct in suggesting that the secular rise in Britain is lower than that in other countries. We report here that in English children there has been an increase over the past 50 years of 12.42 IQ points, averaging 2.48 points per decade. The increase has been in fluid intelligence, the mental power that underlies the acquisition of cognitive skills, rather than in crystallized intelligence, which represents the cognitive skills acquired in a particular culture.

Fluctuations in national levels of neuroticism and extraversion, 1935-1970.

National levels of neuroticism and extraversion in 18 advanced Western nations are measured at intervals from 1935 to 1970. It is shown that levels of neuroticism rose significantly in the nations that suffered military defeat and occupation in the Second World War and then declined during the 1950s to prewar levels. National levels of extraversion have been generally rising over this period.

National differences in extraversion and neuroticism.

A method is proposed for measuring national differences in extraversion and neuroticism from demographic and epidemiological data. The method is to use national prevalence rates of a number of variables and treat them as indices of the levels of extraversion and neuroticism in national populations. The variables taken are the national rates of divorce, illegitimacy, accidents, crime, murder, suicide, alcoholism, chronic psychosis and coronary heart disease; and the per capita consumption of calories, cigarettes and caffeine. Data for these indices are presented for the advanced western nations. The relationship of these variables to extraversion and neuroticism among individuals is used to set up a model for their relationship among nations. The variables were factored by principal components analysis and this yielded two major factors identified as extraversion and neuroticism. The factor scores of each nation on the two factors were then computed. These indicate that the most extraverted nation is the United States and the most introverted is Japan. The most neurotic nation is Austria and the least neurotic is Ireland.