Damian R. Murray

Pathogen prevalence predicts human cross-cultural variability in individualism/collectivism

Pathogenic diseases impose selection pressures on the social behaviour of host populations. In humans (Homo sapiens), many psychological phenomena appear to serve an antipathogen defence function. One broad implication is the existence of cross-cultural differences in human cognition and behaviour contingent upon the relative presence of pathogens in the local ecology. We focus specifically on one fundamental cultural variable: differences in individualistic versus collectivist values. We suggest that specific behavioural manifestations of collectivism (e.g. ethnocentrism, conformity) can inhibit the transmission of pathogens; and so we hypothesize that collectivism (compared with individualism) will more often characterize cultures in regions that have historically had higher prevalence of pathogens. Drawing on epidemiological data and the findings of worldwide cross-national surveys of individualism/collectivism, our results support this hypothesis: the regional prevalence of pathogens has a strong positive correlation with cultural indicators of collectivism and a strong negative correlation with individualism. The correlations remain significant even when controlling for potential confounding variables. These results help to explain the origin of a paradigmatic cross-cultural difference, and reveal previously undocumented consequences of pathogenic diseases on the variable nature of human societies.

On the Origins of Cultural Differences in Conformity: Four Tests of the Pathogen Prevalence Hypothesis

What are the origins of cultural differences in conformity? The authors deduce the hypothesis that these cultural differences may reflect historical variability in the prevalence of disease-causing pathogens: Where pathogens were more prevalent, there were likely to emerge cultural norms promoting greater conformity. The authors conducted four tests of this hypothesis, using countries as units of analysis. Results support the pathogen prevalence hypothesis. Pathogen prevalence positively predicts cultural differences in effect sizes that emerge from behavioral conformity experiments (r = .49, n = 17) and in the percentage of the population who prioritize obedience (r = .48, n = 83). Pathogen prevalence also negatively predicted two indicators of tolerance for nonconformity: within-country dispositional variability (r = —.48, n = 33) and the percentage of the population who are left-handed (r = —.73, n = 20). Additional analyses address plausible alternative causal explanations. Discussion focuses on plausible underlying mechanisms (e.g., genetic, developmental, cognitive).

A Preregistered Study of Competing Predictions Suggests That Men Do Overestimate Women’s Sexual Intent

Errors in perception and judgment are inevitable, but some errors have greater costs than others. Consequently, evolution may bias cognition toward the less costly error (error-management theory; Haselton, Nettle, & Murray, 2015). For example, some researchers have claimed that men typically overestimate women’s sexual interest (Haselton & Buss, 2000) because it was less costly to men’s inclusive fitness for them to infer sexual interest that was absent (overperception) than to overlook sexual interest that was present. Other researchers, however, have argued that evolution should bias behavior but not perception or judgment (e.g., McKay & Efferson, 2010). Following in this tradition, Perilloux and Kurzban (2015) hypothesized that men’s apparent overperception of female sexual interest is an artifact of women understating their own (and other women’s) sexual interest, and that men accurately perceive sexual interest. According to this hypothesis, the gender difference in ratings of female sexual interest is not evidence of a male cognitive bias after all. Perilloux and Kurzban reported results from three studies to support this argument. The results of the first two studies are consistent with previous research. In the critical third study, female participants estimated other women’s sexual intentions (i.e., the likelihood that they intended to have sex with a man) when they engaged in various romantic behaviors with him (e.g., holding hands). Participants were asked to estimate both what other women say their sexual intentions are (“say” question) and what their sexual intentions actually are (“want” question) when they engage in these behaviors. The results indicated that participants thought other women say their sexual intentions are less than what they actually are, which led Perilloux and Kurzban to conclude that males’ sexual perceptions are accurate rather than inflated. We question this conclusion because their finding may be the combined product of question order and Gricean (Grice, 1975) language norms. Because participants were asked the “want” question after the “say” question, they might have concluded that the experimenter expected different responses to the second question (Grice, 1975). If the participants also believed that women are more likely to be coy than otherwise, they would then have given higher ratings for the “want” question than for the “say” question. One way to distinguish Perilloux and Kurzban’s interpretation from this Gricean interpretation is to reverse the question order. A Gricean interpretation predicts that women responding to the “say” question first and women responding to the “want” question first would respond identically, as they would be indicating their beliefs about what other women want. Only when one question is asked after the other would women differentiate their responses to them. In contrast, if Perilloux and Kurzban are correct, question order should be irrelevant. To investigate these competing possibilities, we conducted a preregistered experiment (see www.osf.io/5tejq/) with an online sample of women and varied the order in which Perilloux and Kurzban’s questions were asked. We predicted that responses to the “say” and “want” questions would be equivalent when they were asked first, whereas Perilloux and Kurzban confirmed their prediction that ratings for the “want” question would be higher than ratings for the “say” question regardless of the order of the questions (personal communication, April 19, 2016). 675474 PSSXXX10.1177/0956797616675474Murray et al.Estimates of Women’s Sexual Intent research-article2017

On Disease and Deontology

Threat has been linked to certain facets of moral cognition, but the specific implications of disease threat for moral judgment remain poorly understood. Across three studies, we investigated the role of perceived disease threat in shaping moral judgment and hypothesized that perceived disease threat would cause people to be more sensitive to moral violations (or more “morally vigilant”). All three studies found a positive relationship between dispositional worry about disease transmission and moral vigilance. Additional analyses suggested that this worry was more strongly related to vigilance toward binding moral foundations. Study 3 demonstrated that moral vigilance was higher in individuals for whom the threat of disease was experimentally made salient, relative to individuals in both a neutral and a nondisease threat condition. Taken together, these results suggest that perceived disease threat may influence people’s moral vigilance across moral domains.

Climate and creativity: Cold and heat trigger invention and innovation in richer populations

Nobel laureates, technological pioneers, and innovative entrepreneurs are unequally distributed across the globe. Their density increases in regions toward the North Pole, toward the South Pole, and very close to the Equator. This geographic anomaly led us to explore whether stressful demands of climatic cold and climatic heat (imposed necessities) interact with economic wealth resources (available opportunities) in modulating creative culture—defined here as including both inventive idea generation and innovative idea implementation. Controlling for societal intellectualization, industrialization, and urbanization, results indicated that higher thermal demands, primarily cold stress and secondarily heat stress, hinder creativity in poorer populations but promote creativity in richer populations. Complementing their direct wealth-dependent effects, colder and hotter temperatures also exert indirect wealth-dependent effects on creative culture through lower prevalence of human-to-human transmitted parasitic diseases. Across 155 countries, the resulting ecotheory of creativity accounts for 79% of the variation in creative culture. The findings open up valuable perspectives on the creativity-related consequences of thermal climate—and climate change—in poor and rich populations.

Falling in love is associated with immune system gene regulation

Although falling in love is one of the most important and psychologically potent events in human life, the somatic implications of new romantic love remain poorly understood. Psychological, immunological, and reproductive perspectives offer competing predictions of the specific transcriptional regulatory shifts that might accompany the experience of falling in love. To characterize the impact of romantic love on human genome function, we conducted genome-wide transcriptome profiling of 115 circulating immune cell samples collected from 47 young women over the course of a 2-year longitudinal study. Analyses revealed a selective alteration in immune cell gene regulation characterized by up-regulation of Type I interferon response genes associated with CD1C+/BDCA-1+ dendritic cells (DCs) and CLEC4C+/BDCA-2+ DCs, and a reciprocal down-regulation of α-defensin-related transcripts associated with neutrophil granulocytes. These effects emerged above and beyond the effects of changes in illness, perceived social isolation, and sexual contact. These findings are consistent with a selective up-regulation of innate immune responses to viral infections (e.g., Type I interferons and DC) and with DC facilitation of sexual reproduction, and provide insight into the immunoregulatory correlates of one of the keystone experiences in human life.