Not by g alone: The benefits of a college education among individuals with low levels of general cognitive ability

Matt McGue & James J.Lee:

Secular increases in college completion owe largely to increases among individuals with low levels of GCA.

Individuals with low levels of GCA who complete college experience the same benefits as those with higher levels of GCA.

Personality factors and socio-economic status may partly compensate for the impact of low GCA on college attainment.

In a longitudinal sample of 2593 individuals from Minnesota, we investigated whether individuals with IQs ≤ 90 who completed college experienced the same social and economic benefits higher-IQ college graduates did. Although most individuals with IQs ≤ 90 did not have a college degree, the rate at which they completed college had increased approximately 6-fold in men and 10-fold in women relative to rates in the previous generation. The magnitude of the college effect on occupational status, income, financial independence, and law abidingness was independent of IQ level, a finding replicated using the nationally representative NLSY97 sample. Additional analyses suggested the association of college with occupational status was consistent with a causal effect and that the educational success of individuals with low-average IQs may depend in part on non-ability factors, family socioeconomic status and genetic endowment. We discuss our finding in the context of the recent expansion in college attainment as well as the dearth of research on individuals with low-average IQs.