Our Conclusions Were Tentative, But Appropriate: A Reply to Schnall et al. (2015)

Infection threat shapes our social instincts

We social animals must balance the need to avoid infections with the need to interact with conspecifics. To that end we have evolved, alongside our physiological immune system, a suite of behaviors devised to deal with potentially contagious individuals. Focusing mostly on humans, the current review describes the design and biological innards of this behavioral immune system, laying out how infection threat shapes sociality and sociality shapes infection threat. The paper shows how the danger of contagion is detected and posted to the brain; how it affects individuals’ mate choice and sex life; why it strengthens ties within groups but severs those between them, leading to hostility toward anyone who looks, smells, or behaves unusually; and how it permeates the foundation of our moral and political views. This system was already in place when agriculture and animal domestication set off a massive increase in our population density, personal connections, and interaction with other species, amplifying enormously the spread of disease. Alas, pandemics such as COVID-19 not only are a disaster for public health, but, by rousing millions of behavioral immune systems, could prove a threat to harmonious cohabitation too.

Testing the effects of pathogen threat and sexual strategies on political ideology

Disgust has been consistently associated with greater political conservatism. Two explanations have been proposed for this link. According to a pathogen threat model, disgust serves a pathogen-avoidance function, encouraging more conservative ideology, whereas a sexual strategies model suggests that this link is explained by variability in short-term versus long-term mating goals. In two preregistered studies using a college student and community sample (total N = 1,950), we examined whether experimentally manipulating pathogen threat and mate availability produced differences in political ideology and whether these differences were explained by disgust and sociosexual attitudes. Across both studies, we did not find evidence that manipulating pathogen threat or mate availability resulted in change in political ideology. In Study 1, manipulating mate availability was indirectly associated with greater political conservativism through stronger sociosexual attitudes that favor monogamy. These findings failed to replicate in Study 2. Implications for theory and future research are discussed.

Reexamining the Effect of Gustatory Disgust on Moral Judgment: A Multilab Direct Replication of Eskine, Kacinik, and Prinz (2011)

Eskine, Kacinik, and Prinz’s (2011) influential experiment demonstrated that gustatory disgust triggers a heightened sense of moral wrongness. We report a large-scale multisite direct replication of this study conducted by labs in the Collaborative Replications and Education Project. Subjects in each sample were randomly assigned to one of three beverage conditions: bitter (disgusting), control (neutral), or sweet. Then, subjects made a series of judgments about the moral wrongness of the behavior depicted in six vignettes. In the original study ( N = 57), drinking the bitter beverage led to higher ratings of moral wrongness than did drinking the control or sweet beverage; a contrast between the bitter condition and the other two conditions was significant among conservative ( n = 19) but not liberal ( n = 25) subjects. In the current project, random-effects meta-analyses across all subjects ( N = 1,137, k = 11 studies), conservative subjects ( n = 142, k = 5), and liberal subjects ( n = 635, k = 9) revealed standardized overall effect sizes across replications that were smaller than reported in the original study. Some were in the opposite of the predicted direction; all had 95% confidence intervals containing zero, and all were smaller than the effect size the original authors could have meaningfully detected. Results of linear mixed-effects regressions revealed that drinking the bitter beverage led to higher ratings of moral wrongness than did drinking the control beverage but not the sweet beverage. Bayes factor tests revealed greater relative support for the null than for the replication hypothesis. The overall pattern provides little to no support for the theory that physical disgust via taste perception harshens judgments of moral wrongness.