The Relationship Between Religiousness/Spirituality and Psychometric Intelligence in the United States.

An inverse relationship between religiousness/spirituality (R/S) and psychometric intelligence (IQ) is well-documented in previous literature. However, the studies that have examined group differences on IQ regarding R/S have limited generalizability. The present study contributed to the literature by evaluating IQ among participants identifying as differentially religious/spiritual (i.e., religious only, spiritual only, both religious and spiritual, or neither religious nor spiritual) and among those classified as either Christian/Catholic, Atheist, or Agnostic. Four hundred and thirty-two participants (M age = 37.9; 36% men) participated online via Amazon's Mechanical Turk as part of a larger study and completed a brief measure of IQ, a scale of religiousness and spirituality, and a demographics questionnaire. Correlations between IQ and self-reported religiousness/spirituality were small and negative (Mean r = -0.17), consistent with previous literature. Multivariate analyses of covariance (MANCOVAs) controlling for age, gender, education, and socioeconomic status (operationalized by estimated annual household income) indicated that IQ scores tended to be lowest (p < 0.001) for "religious only" participants (estimated marginal mean [EMM] = 93.0) and highest for "neither religious nor spiritual" participants (EMM = 103.7). Furthermore, IQ scores were significantly lower (ps < 0.001) for Christian/Catholic participants (EMM = 96.7) compared to both Atheist (EMM = 104.9) and Agnostic participants (EMM = 107.5). Discussion of these findings, relationships to previous theoretical and empirical work, limitations of the present study, and directions for future inquiry are provided.