— Cognitive concept
The g-factor (general intelligence)
The single statistical factor underlying performance across all cognitive tasks.
The g-factor (general intelligence factor) is the most replicated finding in all of psychology. First identified by Charles Spearman in 1904, it refers to the fact that performance on virtually every cognitive task correlates positively with performance on every other cognitive task. Someone who's good at vocabulary tests tends to be good at spatial reasoning tests, math tests, and pattern-recognition tests.
What g actually is
Statistically, g is the first principal component when you factor-analyse performance across a diverse battery of cognitive tests. It typically accounts for 40-50% of the variance in cognitive performance. Modern IQ scores are essentially g-loaded measures — and the most g-loaded subtests are also the most predictive of real-world outcomes.
How g relates to IQ
An IQ score is your best statistical estimate of g, expressed on a scale with mean 100 and SD 15. Different tests measure g to different degrees — Raven's Matrices is one of the purest g measures, while specific subtests like vocabulary or arithmetic measure g indirectly through more specific skills.
Why g is controversial
The existence of g is statistically robust. The interpretation is debated. Critics argue that g is an artifact of test design or reflects cultural-educational opportunity rather than a unitary mental ability. Defenders point to g's predictive validity for academic achievement, job performance, and longevity.