Immune response and intergroup bias: Vaccine-induced increases in cytokine activity are associated with worse evaluations of resume for Latina job applicant.

Situational factors can increase people's vulnerability to intergroup bias, including prejudicial attitudes, negative stereotyping, and discrimination. We proposed that increases in inflammatory activity that coincide with acute illness may represent a hitherto unstudied situational factor that increases intergroup bias. The current study experimentally manipulated increases in inflammatory activity by administering the seasonal influenza vaccine or a saline placebo. We quantified inflammatory activity by assessing change in salivary pro-inflammatory cytokines and assessed intergroup bias using a resume evaluation task and self-reported ethnocentrism. Primary analyses focused on a subsample of 117 participants who provided high quality data; robustness analyses included various permutations of lower quality participants. Findings revealed that changes in the cytokine interleukin-1ß (IL-1ß) in response to the vaccine were associated with greater intergroup bias. Among participants who received the vaccine, IL-1ß change was negatively associated with evaluation of a Latina (but not a White woman) applicant's competency and recommended starting salary. Moreover, IL-1ß change was positively associated with ethnocentrism. Overall, results provide support for the hypothesis that acute illness, via the mechanistic role of inflammatory cytokines, affects social cognition in ways that can increase intergroup bias.

Italian validation of the body odor disgust scale.

Introduction: Disgust sensitivity to body odors plays a role in a set of psychological mechanisms supposedly evolved to avoid pathogens. To assess individual differences in body odor disgust, we previously developed the body odor disgust scale (BODS) and validated it in English. The BODS presents six scenarios where disgust could be evoked by smells coming from an internal source and an external source. The present study aimed to validate the BODS in the Italian population and to find further evidence for its structural, construct, and criterion validity. Methods: We used two large samples (N = 1,050, F = 527; and N = 402, F = 203, respectively) that were representative of the Italian population for sex and age. Results: Across these two studies, we confirmed the hypothesized bifactor structure, with all the items loading onto a general body odor disgust sensitivity factor, and on two specific factors related to the internal structure. In terms of construct validity, we found that the BODS converged with pathogen disgust sensitivity of the three-domain disgust scale (TDDS) but was distinct from a general propensity to experience negative emotions. The BODS showed criterion validity in predicting the behavioral intentions toward COVID-19 avoidance behavior, although it did not seem to be incrementally valid when compared to the TDDS pathogen subscale. We also established scalar measurement invariance of the BODS regarding gender and found that women display higher levels of BODS. Discussion: Results from the Italian version of the BODS indicate its structural, construct, nomological and criterion validity. Furthermore, our result on sex differences in disgust sensitivity are consistent with previous literature, and we discuss them in the broader context of cross-cultural and primate findings that points toward a possible evolutionary explanation of this difference.

Association between Disgust Sensitivity during Pregnancy and Endogenous Steroids: A Longitudinal Study.

The emotion of disgust protects individuals against pathogens, and it has been found to be elevated during pregnancy. Physiological mechanisms discussed in relation to these changes include immune markers and progesterone levels. This study aimed to assess the association between steroids and disgust sensitivity in pregnancy. Using a prospective longitudinal design, we analyzed blood serum steroid concentrations and measured disgust sensitivity via text-based questionnaires in a sample of 179 pregnant women during their first and third trimesters. We found positive correlations between disgust sensitivity and the levels of C19 steroids (including testosterone) and its precursors in the Δ5 pathway (androstenediol, DHEA, and their sulfates) and the Δ4 pathway (androstenedione). Additionally, positive correlations were observed with 5α/ß-reduced C19 steroid metabolites in both trimesters. In the first trimester, disgust sensitivity was positively associated with 17-hydroxypregnanolone and with some estrogens. In the third trimester, positive associations were observed with cortisol and immunoprotective Δ5 C19 7α/ß-hydroxy-steroids. Our findings show that disgust sensitivity is positively correlated with immunomodulatory steroids, and in the third trimester, with steroids which may be related to potential maternal-anxiety-related symptoms. This study highlights the complex relationship between hormonal changes and disgust sensitivity during pregnancy.

Visual attention is not attuned to non-human animal targets' pathogenicity: an evolutionary mismatch perspective.

A considerable amount of research has revealed that there exists an evolutionary mismatch between ancestral environments and conditions following the rise of agriculture regarding the contact between humans and animal reservoirs of infectious diseases. Based on this evolutionary mismatch framework, we examined whether visual attention exhibits adaptive attunement toward animal targets' pathogenicity. Consistent with our predictions, faces bearing heuristic infection cues held attention to a greater extent than did animal vectors of zoonotic infectious diseases. Moreover, the results indicated that attention showed a specialized vigilance toward processing facial cues connoting the presence of infectious diseases, whereas it was allocated comparably between animal disease vectors and disease-irrelevant animals. On the other hand, the pathogen salience manipulation employed to amplify the participants' contextual-level anti-pathogen motives did not moderate the selective allocation of attentional resources. The fact that visual attention seems poorly equipped to detect and encode animals' zoonotic transmission risk supports the idea that our evolved disease avoidance mechanisms might have limited effectiveness in combating global outbreaks originating from zoonotic emerging infectious diseases.

Influence of female sex hormones on proactive behavioral and physiological immune parameters.

Women may be more susceptible to infections in the luteal phase, supposedly as a consequence of the hormone progesterone and its immunosuppressive action. While immunosuppression may be important for successful oocyte implantation and pregnancy, it makes women more vulnerable to pathogens. According to theory, to compensate for reduced immunocompetence, women in the luteal phase exhibit proactive behavioral responses, such as disgust and avoidance of disease-associated stimuli, to minimize contagion risk. However, previous studies yielded inconsistent results, and did not account for accompanying proactive immune responses, like the increase of secretory immunoglobin A (sIgA). Here, we assessed the proactive immune response and feelings of disgust associated with disease cues in the comparison of 61 woman with a natural menstrual cycle (31 in the follicular and 30 in the luteal phase) and 20 women taking hormonal contraception (HC). Women rated disease vulnerability and disgust propensity, watched a video displaying people with respiratory symptoms, which was evaluated for its disgust-evoking potential and contagiousness, and provided saliva samples for hormone and sIgA analysis. Women with HC reported a heightened vulnerability to disease compared to naturally cycling women, whereas both the feeling of disgust and the sIgA increase elicited by the disease video were similar across groups, regardless of progesterone. We found a u-shaped relationship between progesterone and baseline sIgA in naturally cycling women, with its nadir during ovulation. Overall, our data do not support a compensatory relationship between the proposed progesterone-induced immunosuppression and heightened disgust or a proactive sIgA response.

Taking Stock and Looking Forward to the Future of Pathogen Politics in Light of New Insights and Recommendations: COVID-19 Threat Was Meaningfully Associated With Support for Liberal Policies in the United States.

Infectious disease outbreaks are expected to predict support for conservative policies. However, earlier studies (January-June, 2020) reached conflicting findings regarding the association between COVID-19 threat and policy preferences in the United States. We revisit this issue by analyzing five nationally representative surveys conducted during the relatively severe periods of the pandemic (August 2020-December, 2020; total N = 82,753). Using Bayesian inference, we find strong evidence that subjective (e.g., fear of infection and pandemic outrage) but not objective (e.g., local cases and deaths) threat predicted support for liberal policies (e.g., immigration and universal health care). Meta-analyses revealed that the estimates depend on the type of subjective (.05 ≥ r ≤ .60) or objective (.00 ≥ r ≤ .14) COVID-19 threat. We propose an emotion-mediated dual-process model of pathogen management suggesting that infectious disease outbreaks activate both avoidance and caregiving motives that translate, respectively, into support for right-wing and left-wing policies.

Introduction to the special issue: evolutionary and biopsychosocial perspectives on sickness communication.

Here, we introduce the EMPH special issue on Evolutionary and Biopsychosocial Perspectives on Sickness Communication. This Commentary provides an overview of each article and places them in the wider context of sickness as a social phenomenon with verbal and nonverbal signals. This Commentary, and the special issue, in general, calls for greater attention to these signals that can affect pathogen transmission and may be at the evolutionary root of our caregiving systems and behaviours.

Genetic variation in parasite avoidance, yet no evidence for constitutive fitness costs.

Behavioral avoidance of parasites is a widespread strategy among animal hosts and in human public health. Avoidance has repercussions for both individual and population-level infection risk. Although most cases of parasite avoidance are viewed as adaptive, there is little evidence that the basic assumptions of evolution by natural selection are met. This study addresses this gap by testing whether there is a heritable variation in parasite avoidance behavior. We quantified behavioral avoidance of the bacterial parasite Serratia marcescens for 12 strains of the nematode host Caenorhabditis elegans. We found that these strains varied in their magnitude of avoidance, and we estimated the broad-sense heritability of this behavior to be in the range of 11%-26%. We then asked whether avoidance carries a constitutive fitness cost. We did not find evidence of one. Rather, strains with higher avoidance had higher fitness, measured as population growth rate. Together, these results direct future theoretical and empirical work to identify the forces maintaining genetic variation in parasite avoidance.

Ingroup favoritism on perceived risk of infectious diseases.

Humans live in social groups; thus, infectious diseases may threaten human health and safety. Do individuals exhibit ingroup favoritism or ingroup devaluation when faced with varying risks of infectious diseases? We generated relatively realistic disease scenarios to examine this question. We reported the results from three experiments in which we tested individuals' perceived disease risk from ingroup and outgroup members under high- and low-risk conditions. Experiment 1 used a realistic influenza scenario, and Experiments 2 and 3 used a realistic scenario of exposure to coronavirus disease 2019 (COVID-19). All three experiments showed that perceived disease risk was significantly lower from ingroup members than from outgroup members and significantly lower in low-risk conditions than in high-risk conditions. Furthermore, the perceived disease risk was significantly lower from ingroup members than from outgroup members in high-risk conditions but did not significantly differ in low-risk conditions, as in Experiment 1's influenza scenario and Experiment 2's COVID-19 vaccination scenario. This suggests that ingroup favoritism is flexible. The results support ingroup favoritism and the functional flexibility principle in response to disease threats according to perceived disease risk.

Looking beyond vaccines: Cultural tightness-looseness moderates the relationship between immunization coverage and disease prevention vigilance.

Advancements in vaccination technologies mitigate disease transmission risks but may inadvertently suppress the behavioral immune system, an evolved disease avoidance mechanism. Applying behavioral immune system theory and utilizing robust big data analytics, we examined associations between rising vaccination coverage and government policies, public mobility, and online information seeking regarding disease precautions. We tested whether cultural tightness-looseness moderates the relationship between mass immunization and disease prevention vigilance. Comprehensive time series analyses were conducted using American data (Study 1) and international data (Study 2), employing transfer function modeling, cross-correlation function analysis, and meta-regression analysis. Across both the US and global analyses, as vaccination rates rose over time, government COVID-19 restrictions significantly relaxed, community mobility increased, and online searches for prevention information declined. The relationship between higher vaccination rates and lower disease prevention vigilance was stronger in culturally looser contexts. Results provide initial evidence that mass immunization may be associated with attenuated sensitivity and enhanced flexibility of disease avoidance psychology and actions. However, cultural tightness-looseness significantly moderates this relationship, with tighter cultures displaying sustained vigilance amidst immunization upticks. These findings offer valuable perspectives to inform nuanced policymaking and public health strategies that balance prudent precautions against undue alarm when expanding vaccine coverage worldwide.

Discriminating between sick and healthy faces based on early sickness cues: an exploratory analysis of sex differences.

Background and objectives: It has been argued that sex and disease-related traits should influence how observers respond to sensory sickness cues. In fact, there is evidence that humans can detect sensory cues related to infection in others, but lack of power from earlier studies prevents any firm conclusion regarding whether perception of sickness cues is associated with sex and disease-related personality traits. Here, we tested whether women (relative to men), individuals with poorer self-reported health, and who are more sensitive to disgust, vulnerable to disease, and concerned about their health, overestimate the presence of, and/or are better at detecting sickness cues. Methodology: In a large online study, 343 women and 340 men were instructed to identify the sick faces from a series of sick and healthy photographs of volunteers with an induced acute experimental inflammation. Participants also completed several disease-related questionnaires. Results: While both men and women could discriminate between sick and healthy individuals above chance level, exploratory analyses revealed that women outperformed men in accuracy and speed of discrimination. Furthermore, we demonstrated that higher disgust sensitivity to body odors is associated with a more liberal decision criterion for categorizing faces as sick. Conclusion: Our findings give strong support for the human ability to discriminate between sick and healthy individuals based on early facial cues of sickness and suggest that women are significantly, although only slightly, better at this task. If this finding is replicated, future studies should determine whether women's better performance is related to increased avoidance of sick individuals.

Pathogen disgust is associated with interpersonal bias among healthcare professionals.

Background and objectives: Pathogen avoidance is a fundamental motive that shapes many aspects of human behavior including bias against groups stereotypically linked to disease (e.g. immigrants, outgroup members). This link has only been examined in convenience samples and it is unknown how pathogen avoidance processes operate in populations experiencing prolonged and heightened pathogen threat such as healthcare professionals. We examined whether healthcare professionals demonstrate the same link between pathogen disgust and intergroup bias as has been documented among the general population. Methodology: Participants (N = 317; 210 healthcare professionals) were recruited using snowball sampling to take an online survey. Participants completed the Three Domain Disgust Scale to assess pathogen, sexual and moral disgust. Participants then rated their perceptions of a fictitious immigrant group ('Krasneeans') and the degree to which they endorsed group-binding moral values. Results: Compared to control participants, healthcare professionals reported lower levels of pathogen disgust, but not sexual or moral disgust. However, regardless of profession, higher pathogen disgust was associated with viewing Krasneeans as less likeable and more unclean. Additionally, regardless of profession, higher pathogen disgust was associated with greater endorsement of group-binding moral values, although healthcare professionals reported greater overall endorsement of group-binding moral values than did control participants. Conclusions and implications: Although healthcare professionals demonstrated lower levels of pathogen disgust, they nevertheless exhibited largely the same relationship between pathogen disgust and interpersonal biases as did control participants. One practical implication of this association is that pathogen avoidance motives may contribute to inequitable patient treatment in healthcare settings.

I Got it. Perceived Infectability and Germ Aversion after Covid-19 Infection.

Objective: The COVID-19 pandemic has offered a unique opportunity to test evolutionary hypotheses on the functionality of the behavioral immune system. The aim of the present study was to ascertain if a previous infection with COVID-19 was associated with increased levels of perceived infectability and germ aversion. Based on the calibration hypothesis, we predicted that the activation of the behavioral immune system was greater in those participants who had been infected compared to those who reported no previous COVID-19 infection. Method: The sample included 2072 participants who completed an online survey between March 1 and April 10, 2022 when the Italian population was facing the third wave of the COVID-19 pandemic. To measure the activation of the behavioral immune system, we used the Perceived Vulnerability to Disease (PVD) scale. Results: Perceived infectability was significantly greater in those participants who had been infected compared to those who reported no previous COVID-19 infection but there was no significant difference between the two groups in terms of germ aversion.Conclusions Overall, our findings suggest that individual differences in the activation of the behavioral immune system were marginally affected by a personal history of COVID-19 infection. A possible explanation is that the environmental sensitivity of the behavioral immune system is tuned more on chronic disease threat (i.e., ecologies with higher pathogen load) than on situational disease threat (e.g., a pandemic or disease outbreak like the COVID-19 pandemic).

First impressions of a new face are shaped by infection concerns.

Along with a classical immune system, we have evolved a behavioral one that directs us away from potentially contagious individuals. Here I show, using publicly available cross-cultural data, that this adaptation is so fundamental that our first impressions of a male stranger are largely driven by the perceived health of his face. Positive (likeable, capable, intelligent, trustworthy) and negative (unfriendly, ignorant, lazy) first impressions are affected by facial health in adaptively different ways, inconsistent with a mere halo effect; they are also modulated by one's current state of health and inclination to feel disgusted by pathogens. These findings, which replicated across two countries as different as the USA and India, suggest that instinctive perceptions of badness and goodness from faces are not two sides of the same coin but reflect the (nonsymmetrical) expected costs and benefits of interaction. Apparently, pathogens run the show-and first impressions come second. Lay Summary: Our first impressions of strangers (whether they seem trustworthy, intelligent, unfriendly, or aggressive) are shaped by how healthy their faces look and by our unconscious motivation to avoid infections. Bad and good impressions turn out to reflect the concrete, potentially vital, expected costs and benefits of interacting with our fellow humans. Apparently, pathogens run the show-and first impressions come second.

Resting parasympathetic activity is associated with malodor-induced change in perceived foreignness of speakers.

INTRODUCTION: To protect against infection, individuals have evolved context-dependent pathogen-avoidant strategies, including selective social behaviors aimed at avoiding foreign individuals who may possess greater risk of infection. Parasympathetic nervous system (PNS) activity is associated with social engagement and regulation of the classical immune system but has not been widely investigated in relation to changes in intergroup perception and the behavioral immune system. METHOD: The current research investigated the relationship between parasympathetic activity and perceived foreignness of in and outgroup speakers during exposure to a pathogen-relevant odor (butyric acid). High-frequency heart rate variability was measured at rest and while participants rated foreignness of speakers with and without the odor present. RESULTS: Findings show that exposure to the odor was associated with higher foreignness perceptions of outgroup speakers and lower foreignness perceptions of ingroup speakers. This effect was especially evident among individuals with higher resting parasympathetic activity. CONCLUSION: These results suggest that the PNS may play a role in changes in social perceptions during a behavioral immune response.

Beyond the surface: accounting for confounders in understanding the link between collectivism and COVID-19 pandemic in the United States.

According to the parasite-stress theory, collectivism serves as a trait of ingroup assortative sociality, providing defense against infectious diseases. This study investigated the association between cultural collectivism and COVID-19 severity at the state (Study 1: N = 51), county (Study 2: N = 3,133), and daily (Study 3: N = 52,806) levels from the beginning of 2020 to the end of 2022. State-level collectivism was assessed using two distinct measures: the U.S. collectivism index, focusing on social interconnectedness and interdependence, and the subjective-culture individualism-collectivism index (reversed), capturing attitudes and beliefs related to religion, abortion, and same-sex marriage. By employing random-intercept multilevel models, the results demonstrated significant and negative effects of state-level collectivism, as measured by the U.S collectivism index, on COVID-19 cases per million, COVID-19 deaths per million, and composite COVID-19 severity index, after controlling for confounding factors, such as socioeconomic development, ecological threats, disease protective behaviors, cultural norms, and political influences. A mini meta-analysis (Study 4: N = 9) confirmed the significance of these effects across studies. These findings supported the proactive role of collectivism in defending against the novel coronavirus in the United States, aligning with the parasite-stress theory of sociality. However, the subjective-culture individualism-collectivism index (reversed) did not exhibit a significant relationship with COVID-19 severity when confounding factors were considered. The high correlation between the subjective-culture individualism-collectivism index (reversed) and the controlled variables suggested shared variance that could diminish its impact on COVID-19 outcomes. Accordingly, the present findings underscore the significance of accounting for confounding factors when examining the association between collectivism and COVID-19 severity at population level. By considering relevant confounding factors, researchers could gain a comprehensive understanding of the complex interplay between cultural collectivism and its influence on COVID-19 severity. Overall, this research contributes to our understanding of how cultural collectivism shapes the COVID-19 pandemic in the United States, emphasizing the importance of adjusting for confounding effects in population level studies.

How does disgust regulate social rejection? a mini-review.

The need to belong is a fundamental aspect of human nature. Over the past two decades, researchers have uncovered many harmful effects of social rejection. However, less work has examined the emotional antecedents to rejection. The purpose of the present article was to explore how disgust--an emotion linked to avoidance and social withdrawal--serves as an important antecedent to social rejection. We argue that disgust affects social rejection through three routes. First, disgust encourages stigmatization, especially of those who exhibit cues of infectious disease. Second, disgust and disease-avoidance give rise to cultural variants (e.g., socially conservative values and assortative sociality), which mitigate social interaction. Third, when the self is perceived as a source of contamination, it promotes shame, which, subsequently, encourages withdrawal from social interaction. Directions for future research are also discussed.

Exploring changes in violence across two waves of the COVID-19 pandemic in Richmond, VA.

The first wave of the COVID-19 pandemic carried with it an increase in violence in the United States and abroad. The proportion of violence cases involving firearms also increased during this time, yet little research has examined these effects using data from the second wave of COVID infections. Explanations for these documented increases in gun violence put forward by scholars include increased firearm purchases, alcohol consumption, unemployment, and organized crime activity. The current work examined these trends in Richmond, VA. We collected data on patients (N = 1744) presenting with violent injuries from 2018 to 2022 from the emergency department of a Level-1 Trauma Center in Richmond, VA. Data were coded on the basis of whether they presented before the pandemic, during the first wave, or during the second wave. Logistic binomial regressions revealed that the risk of gunshot wounds increased by 32% during the first wave and 44% during the second wave, relative to the pre-COVID period, but that the increase between the first and second wave was not significant. These findings held after controlling for victim age, race, sex, and injury severity. Further analyses revealed that these effects were specific to violent injury, as we found no increase in firearm use among self-injury cases. The heightened violence reported during the COVID-19 pandemic was also observed in Richmond, VA. Gun violence in particular increased over time as other forms of violence (i.e., assaults, stabbings, and self-harm) decreased.

Functional Heuristics of Disease Transmission from Physical Deformities in Food Preferences.

Ostensibly serving to restrict contact with disease vectors, humans exhibit aversion toward cues heuristically inferred as pathogenic. This restriction could lead perceivers to downregulate their interest in food consumption, even if such cues may not connote actual disease threats. This proclivity to avoid disease led us to consider how heuristic disease cues inform interest in foods. Participants evaluated a hypothetical food preparer that varied in the presence of heuristic cues to disease transmission (i.e., physical deformities versus healthy control). Individuals with low levels of perceived infectability were more discerning of the social target as a function of disease cues, whereas heightened levels of this trait fostered an overall aversion to targets regardless of health status. Results provide continued evidence for how pathogen avoidance motives compete with other somatic motives.

Disgust sensitivity and support for immigration across five nations.

Immigration has become a focal debate in politics across the world. Recent research suggests that anti-immigration attitudes may have deep psychological roots in implicit disease avoidance motivations. A key implication of this theory is that individual differences in disease avoidance should be related to opposition to immigration across a wide variety of cultural and political contexts. However, existing evidence on the topic has come almost entirely from the United States and Canada. In this article, we test the disease avoidance hypothesis using nationally representative samples from Norway, Sweden, Turkey, and Mexico, as well as two diverse samples from the United States. We find consistent and robust evidence that disgust sensitivity is associated with anti-immigration attitudes and that the relationship is similar in magnitude to education. Overall, our findings support the disease avoidance hypothesis and provide new insights into the nature of anti-immigration attitudes.