Education's Effect on Mental Ability

Christopher Winship, Harvard University

I use novel methods to estimate the effects of additional high school and college education on respondents' mental ability. Using the NLSY, I construct synthetic cohorts of individuals with different years of final schooling. I then use longitudinal methods to estimate what their mental ability as measured by the AFQT would have been if they had remained in school an additional year. Surprising results are obtained. For individuals in 12th grade, an additional year of schooling would increase their AFQT scores by .208 standard deviations, consistent with previous research. However, 60% of this effect is due to being presently in school, whereas on 40% is "permanent." I conclude that mental ability, at least as measured by the AFQT, appears to be like some kinds of music and athletic ability - there are large innate differences, training is critical to performance, and being "in shape" has a substantial effect on performance.