It is the broad Conservative Syndrome that correlates negatively with cognitive abilities, and religiosity is only a part of it. Cognitive ability is becoming an increasingly important predictor of social conservatism

Conservative Syndrome and the understanding of negative correlations between religiosity and cognitive abilities. Lazar Stankov, Jihyun Lee. Personality and Individual Differences, Volume 131, 1 September 2018, Pages 21–25. https://doi.org/10.1016/j.paid.2018.04.016

Abstract: We present new data about the correlation between religiosity and cognitive abilities. At the individual level of analysis the correlation is r = −0.199 and at the country level of analysis the correlation is r = −0.420 with a test of fluid intelligence and r = −0.536 with PISA 2015 science scores. These correlations can be reduced by partialling out measures of traditional values, power distance and conservatism/liberalism. They can also be reduced by partialling out economic and political indices. Our findings indicate that it is the broad Conservative Syndrome that correlates negatively with cognitive abilities, and religiosity is only a part of it. Cognitive ability is becoming an increasingly important predictor of social conservatism.

Keywords: Religiosity; Conservative Syndrome; Cognitive ability