Seventy years, 1000 samples, and 300,000 SPM scores: A new meta-analysis of Flynn effect patterns

Several studies have investigated and found the gradual rise in IQ over time or the Flynn effect (FE) but inconsistent results on the FEs across types of countries and age groups were reported. The current cross-temporal meta-analysis aimed to examine the temporal correlations between mean IQ scores from Standard Progressive Matrices and year of publication, moderated by types of countries and age groups covering seven decades (1948–2020). The given relationships were weighted by sample sizes. The dataset included 1038 independent samples (N = 299,155) from 72 countries. The results generally supported the FE with the IQ gain of 0.22 points per year, but the magnitudes of the IQ gains depended on types of countries and age groups. Stronger FEs were evident in middle-income countries and younger generations. A multicausal explanatory framework should be utilized to explain the underlying mechanism of the secular IQ gains across factors.