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.

Pseudo-Contamination and Memory: Is There a Memory Advantage for Objects Touched by "Morphologically Deviant People"?

Memory plays an important role in the behavioral immune system (BIS; Schaller in Psychological Inquiry, 17(2), 96-101, 2016a), a proactive immune system whose ultimate function is to make organisms avoid sources of contamination. Indeed, it has been found that objects presented next to sick people are remembered better than objects shown next to healthy people-representing a contamination effect in memory. In the present studies, we investigated this memory effect in relation to "pseudo-contaminated" sources, that is to say, people exhibiting cues ultimately evoking the threat of contamination but objectively posing no such threat in terms of disease transmission. Common objects were shown next to photographs of people having three kinds of morphological deviations-obesity (study 1), scars and burns (study 2), strange eyes (study 3)-or no morphological deviation. Contrary to our expectations, we found that "pseudo-contaminated objects" were not remembered better than "non-contaminated objects," whereas discomfort ratings of the idea of touching the same objects were clearly higher with morphologically deviant people. Memory mechanisms do not seem to be mobilized by "pseudo-contamination" sources which are not directly related to infection risk.

Pathogen Threat and In-group Cooperation

Disease-causing parasites and pathogens play a pivotal role in intergroup behavior. Previous studies have suggested that the selection pressure posed by pathogen threat has resulted in in-group assortative sociality, including xenophobia and in-group favoritism. While the current literature has collated numerous studies on the former, strikingly, there has not been much research on the relationship between pathogen threat and in-group cooperation. Drawing upon prior studies on the function of the behavioral immune system (BIS), we argued that the BIS might facilitate cooperation with in-group members as a reactive behavioral immune response to pathogen threat. More specifically, we held that individuals might utilize cooperative behavior to ensure that they can receive social support when they have contracted an infectious disease. We reviewed existing findings pertaining to the potential role of the BIS in in-group cooperation and discussed directions for future studies.

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.

Disease Salience Effects on Desire for Affiliation With In-Group and Out-Group Members: Cognitive and Affective Mediators

This study tested the hypothesis that threats related to infectious diseases would make persons less willing to affiliate with out-groups and that feelings of disgust and beliefs about the out-group members would mediate this effect. To test this hypothesis, American participants of European descent were presented with either a disease threat or control threat. Then they were shown a photograph of someone of the same race or different race. Participants were asked to indicate whether they would avoid the target person and to state their emotional and cognitive responses to the person. As predicted, disease salience decreased the desire to affiliate with out-group members, and both feelings of disgust and beliefs about the infection risk posed by the target person mediated this relationship.

A Contagious Other? Exploring the Public's Appraisals of Contact with 'Mental Illness'

Mental illness has recurrently been found to be Othered by the lay public, although few researchers have examined the affective and implicit processes involved. To explore this, we triangulated facial electromyography (EMG), self-reports, and individual interview data, finding participants to Other mental illness, a process that involved disgust, fear and pity. Furthermore, mental illness was considered to have the potential to permeate, posing a contagious threat. This research highlights the need to fully explore the forms of understanding, which maintain mental-health related stigma, including beliefs about contamination, and the implications this may have for the design of anti-stigma campaigns.