Home > Archive > Volume 64, No. 3 > This paper

Does Conservative Religiousness Promote Selection for Intelligence? An Analysis of the Vietnam Experience Study

Edward Dutton and Emil O. W. Kirkegaard


Published: 2024/03/01


Previous research has indicated that religiousness may moderate the negative effect of intelligence on fertility which is found in modern populations. We studied this question using the Vietnam Experience Study, a public dataset of 4,462 American Vietnam-era veterans. In line with prior research, we found that, net of controls, intelligence predicted lower fertility, [I]β[/I] = -0.06 ([I]p[/I] = .003), and religiousness predicted higher fertility [I]β[/I] = 0.21 ([I]p[/I] < .001). The expected interaction, intelligence * religiousness, was also found ([I]β[/I] = 0.06 ([I]p[/I] = .002). The results show that above average religiousness is associated with a neutral or positive fertility pattern regarding intelligence, while average or below average religiousness is associated with a negative fertility pattern. The results held when the White subsample was analyzed separately (intelligence · religiousness [I]β[/I] = 0.09 [I]p[/I] < .001). Finally, the negative relationship between intelligence and fertility seen in the dataset showed a strong Jensen Effect in the expected direction ([I]n[/I] = 19 tests, [I]r[/I] = −.73). Keywords: Vietnam Experience Study, Intelligence, Fertility

   Download PDF