Analysis of 48 countries in the 2000–2018 PISA tests: Mainly positive Flynn effects in economically less developed countries, negative Flynn effects in the economically most advanced countries

Ongoing trends of human intelligence. Gerhard Meisenberg, Richard Lynn. Intelligence, Volume 96, January–February 2023, 101708. https://doi.org/10.1016/j.intell.2022.101708

Abstract: The aim of the study is to estimate the most recent trends of intelligence world-wide. We find that the most recent studies report mainly positive Flynn effects in economically less developed countries, but trivial and frequently negative Flynn effects in the economically most advanced countries. This is confirmed by an analysis of 48 countries in the 2000–2018 PISA tests, showing that high pre-existing IQ and school achievement are the best predictors of declining test scores. IQ gaps between countries are still large (e.g., 19 IQ points in PISA between East Asia and South Asia) but are diminishing world-wide. We predict that these trends, observed in adolescents today, will reduce cognitive gaps between the working-age populations of countries and world regions during coming decades. As is predicted by the well-established relationship between intelligence and economic growth, there is already evidence that the ongoing cognitive convergence is paralleled by global economic convergence. These developments raise questions as to how long this cognitive and economic convergence will continue, whether it will eliminate cognitive and economic gaps between countries entirely, and whether a condition with high levels of cognitive ability and economic prosperity is sustainable long-term.

Introduction

The last century has seen two developments in intelligence research that are sufficiently profound to be called “scientific revolutions” (Kuhn, 1962): the importance of genetics for individual differences, and the discovery that intelligence changes on the historical time scale, with major rises of intelligence having taken place during the 20th century. Jim Flynn's work was at the center of the second of these scientific revolutions. Scattered reports about rising intelligence had appeared since the 1930s (Lynn, 2013), but the pervasive nature of secular intelligence gains was not recognized until Flynn's work during the 1980s, when he showed rising IQ in the United States and world-wide (Flynn, 1984, Flynn, 1987).

Flynn did not fully grasp the significance of his findings at once. In his 1987 paper (p. 187), he concluded: “The Ravens Progressive Matrices Test does not measure intelligence but rather a correlate with a weak causal link to intelligence; the same may apply to all IQ tests.” Elsewhere he asks: “Why aren't we undergoing a renaissance unparalleled in human history? …why aren't we duplicating the golden days of Athens or the Italian Renaissance?” (Holloway, 1999). At that time, Flynn did not believe that “real” intelligence could have risen so much. Only later did he fully acknowledge the reality and importance of rising intelligence, for the functioning of a modern economy and even for the moral progress he saw during the 20th century (Flynn, 2013, Flynn, 2014).

Two major meta-analyses have confirmed the ubiquity of test score gains (Pietschnig & Voracek, 2015; Trahan, Stuebing, Fletcher, & Hiscock, 2014). We also know that the Flynn effect is not strongest on the most g-loaded tests (te Nijenhuis, 2013; te Nijenhuis & Van Der Flier, 2013). This suggests that the causal factors that determine individual differences in intelligence, and thereby the correlations between its cognitive components, are different from the factors that have changed the intelligence levels of entire populations over time. It has been claimed that, with proper controls included, the Flynn effect has been stronger on tests requiring more “abstract” thinking (Armstrong et al., 2016; Must, Must, & Mikk, 2016). More generally, gains on fluid intelligence have been stronger than gains on crystallized intelligence, at least in most of the times and places for which we have informative data. Some abilities included in the g nexus did not show any evidence of Flynn effects, including reaction time (e.g., Nettelbeck & Wilson, 2004), digit span (Gignac, 2015; Woodley of Menie & Fernandes, 2015), and ability-based emotional intelligence (Pietschnig & Gittler, 2017).

There is general agreement that the Flynn effect, and perhaps also its reversal in some countries, is caused by environmental changes rather than genetics (Bratsberg & Rogeberg, 2018). Schooling is a likely candidate considering that the educational level of the population has risen massively over time (Schofer & Meyer, 2005) and that each year of additional school attendance during adolescence raises the IQ by 1–5 points (Ritchie & Tucker-Drob, 2018); and like the Flynn effect, schooling gains are not on g, but on specialized cognitive skills (Ritchie, Bates, & Deary, 2015). Improved nutrition is another likely contributor to Flynn effects (Lynn, 1990).

Intelligence is important for human societies. Weede and Kämpf (2002) were the first to present evidence that the rate of economic growth is predicted mainly by two variables: initial per capita GDP, and average intelligence of the population. Low initial per capita GDP and high intelligence is the combination that favors rapid economic growth. This key finding has been confirmed in multiple further studies (e.g., Francis & Kirkegaard, 2022; Jones & Schneider, 2006; Meisenberg, 2012, Meisenberg, 2014a). It implies that in the short term, countries gravitate towards a level of prosperity that is commensurate with their level of intelligence. On longer time scales, this observation predicts that countries with rising intelligence become richer while those with declining intelligence become poorer.

Combining these findings with the earlier conclusion that the Flynn effect is caused by environmental improvements associated with economic development, such as high-intensity educational systems and the elimination of childhood malnutrition, we can conclude that since the industrial revolution, economic development and the Flynn effect have reinforced each other in an upward spiral, a positive feedback that has created modern industrial society (Meisenberg, 2014a, Meisenberg, 2014b). It implies that the maintenance of high intelligence is a requirement for the maintenance of well-functioning and prosperous societies. It is this theory which motivates our investigations into the current and projected future trajectories of human intelligence in the countries of the world. The importance of this research is underscored by recent reports about the end of the Flynn effect, and even its reversal, especially in several European countries (Dutton, van der Linden, & Lynn, 2016). In the present study, we investigate which countries of the world still have positive Flynn effects, and where intelligence is stagnating or declining.