Intelligence and religiosity: Within families and over time

We study the effect of intelligence (General Mental Ability) on religiosity using research designs that allow for stronger causal inferences compared to previous research in this area. First, we examine how between-siblings differences in intelligence are related to differences in their religiosity. Second, we examine how intelligence is related to changes in religiosity over time. The results of both designs suggest that intelligence has a strong negative effect on religiosity. In addition, our results also suggest that intelligence interacts with age in determining religiosity: the more intelligent the person, the stronger the negative effect of age on religiosity.