Conscientiousness, Education, and Longevity of High-Ability Individuals

In this paper, I investigate whether investments in higher education causally affect longevity. I also investigate the role of personality skills in producing longevity, taking into account their potential interaction with education. The causal status of higher education in affecting health and longevity is unclear in the literature, largely because of unknown confounding factors, reverse causality, and difficulty in finding instrumental variables that are both valid and sufficiently strong to reliably estimate the causal effect of higher education on longevity. I examine whether there are confounding factors among early cognitive and personality skills, and estimate the causal effect by controlling for latent confounding personality factors and for the reverse causality. I use measures of personality skills that were shown to be close to the established Big Five taxonomy of personality, and find that a personal skill of Conscientiousness has strong effects on both education and longevity. I estimate a model that uses Conscientiousness and education as arguments of a production function for longevity. The model accounts for the endogeneity of education, measurement error in the proxies for Conscientiousness, and the interaction between education and Conscientiousness in producing longevity. I estimate the model using the 1922–1991 Terman life cycle data of children with high ability, a prospective study with unique life cycle information including early health variables, childhood personality and IQ measures, mortality observations, and detailed background characteristics. My results show that while both Conscientiousness and education increase longevity for males, the effect of Conscientiousness on longevity is only strong at low levels of education, and the effect of education on longevity is especially strong at low levels of Conscientiousness. In addition, I show that a failure to account for Conscientiousness leads to an upward bias in the estimate of the effect of education on longevity. The bias from omitting Conscientiousness is comparable to the bias from omitting all other control variables in the model including parental education and occupation. For females, I find that the effects of education and Conscientiousness are not precisely determined. I argue that this lack of strong effects for females born around 1910 might not be generalizable to the contemporary female population.