To g or Not to g? A Cross-Domain, Subtest-Level Investigation of the Flynn Effect Across Ages 7-15 Years

For decades, researchers have debated whether the magnitude of the Flynn Effect-intergenerational increases in mean IQ scores-varies across cognitive domains and subdomains, and whether the Flynn Effect reflects gains in general cognitive ability (g). We conducted a cross-domain, subtest-level investigation of the Flynn Effect across middle childhood and early adolescence (ages 7-15 years, N = 1187, 89% White, 9% Black, 52% female) in longitudinal cognitive ability data collected prospectively between 1957 and 1999 using three versions of the Wechsler Intelligence Scale for Children. Results provided clear evidence of the Flynn Effect as both increases in mean IQ score across generational cohort and decreases in mean IQ across test versions. Flynn Effect magnitude differed substantially across domains and subtests. Performance IQ gains were larger than full-scale and verbal IQ gains in test version-based analyses, but cohort-based estimates showed modest differences in an opposite pattern (VIQ > FSIQ > PIQ). Variance in Flynn Effect magnitude across subtests did not follow a discernible pattern. The strength of the Flynn Effect on individual subtests was not strictly proportional to each subtest's g-loading, with performance IQ subtests showing larger increases than would be expected given their g-loadings and verbal subtests showing smaller-than-expected gains.