Summary: Feeling disgusted or queasy when you encounter unpleasant sights, smells, or tastes may be an evolved response that helps protect people from infection by encouraging avoidance of potential sources of pathogens.
Source: Washington State University
New research published in the Proceedings of the National Academy of Sciences on Feb. 15 suggests that disgust plays a protective role in reducing exposure to infectious agents.
This study is the first to directly test whether individuals who report higher sensitivity to pathogen-related disgust actually encounter fewer pathogens in their everyday environments and, as a result, show fewer signs of infection.
“We found that people with higher levels of disgust had lower levels of inflammatory biomarkers that indicated recent bacterial or viral infection,” said Aaron Blackwell, an associate professor of anthropology at Washington State University and a co-author on the paper. “The results indicate that disgust can function as an infection-avoidance mechanism, but its effectiveness depends on the local environment and the practical ability to avoid certain risks.”
The research team, led by Tara Cepon-Robins of the University of Colorado, Colorado Springs and including Blackwell, analyzed household data from three indigenous Shuar communities in Ecuador. All three communities face a relatively high burden of pathogens, but they differ in levels of market integration, economic development, and reliance on traditional subsistence activities such as hunting and small-scale agriculture.
Overall, the investigators observed that disgust sensitivity offered greater protection in settings where people could realistically avoid sources of contamination. In communities with more market integration—where residents had better access to clean water and could buy food rather than relying entirely on foraged or hunted sources—higher disgust sensitivity was associated with lower markers of bacterial and viral infection.
In contrast, in communities that depend more heavily on subsistence activities, daily life often requires contact with potentially contaminated soil, water, or animal waste. In those contexts the study found lower average disgust sensitivity, and avoidance was more difficult or costly, which reduced the protective effect of disgust.
The researchers also found that disgust did not protect equally against all types of pathogens. “High disgust sensitivity was linked to fewer bacterial and viral infections, but it did not reliably reduce parasitic worm infections common in the area,” Blackwell explained. Parasitic helminths are often transmitted via soil and other environmental routes that are hard to avoid while hunting, farming, or otherwise engaging in subsistence work.
The study also highlights the limits of disgust in the context of pandemics. Blackwell, who has written on the role of pathogen-avoidance psychology during pandemics in Trends in Cognitive Sciences, noted that disgust cues are often absent for pathogens transmitted by asymptomatic carriers. “Disgust doesn’t protect us very well against pandemics like COVID-19 in part because many infected people show no symptoms,” he said. “Without visible or sensory cues, there’s nothing obvious to trigger avoidance.”
Charles Darwin was among the first to propose that disgust evolved to steer humans away from spoiled food and other contamination risks. While many studies have supported this idea, this is the first research to directly link higher pathogen disgust sensitivity with reduced current indicators of infection across real-world communities.
The findings support the view that disgust is an evolved emotion that contributes to disease avoidance, and that the strength of disgust responses is calibrated by local costs and benefits—shaped by factors such as sanitation, market access, and subsistence demands.
This research was conducted as part of the Shuar Health and Life History Project. The collaborative team included researchers from Washington State University, the University of Colorado, Colorado Springs, Washington University in St. Louis, Northern Arizona University, Baylor University, the University of Oregon, and Queens College, City University of New York.
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Source: Washington State University
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Original Research: Closed access. “Pathogen disgust sensitivity protects against infection in a high pathogen environment” by Aaron Blackwell et al., Proceedings of the National Academy of Sciences (PNAS)
Abstract
Pathogen disgust sensitivity protects against infection in a high pathogen environment
Disgust is hypothesized to be an evolved emotion that promotes avoidance of pathogen-related stimuli and behaviors. Individuals with higher pathogen disgust sensitivity (PDS) are predicted to encounter fewer pathogens and therefore suffer fewer infections, but this relationship had not been tested directly in natural settings. PDS is also thought to be locally calibrated: its expression should reflect the types of pathogens common in a community and the relative costs and benefits of avoidance.
Market integration—measured as the extent to which people produce for or consume from market-based economies—alters sanitation, hygiene, and lifestyles, thereby changing the costs and benefits of avoiding pathogens and influencing PDS. The study examined associations among PDS, market-related lifestyle factors, and measures of bacterial, viral, and macroparasitic infection at individual, household, and community levels. Data came from 75 participants (ages 5–59) across 28 households in three Ecuadorian Shuar communities characterized by high pathogen exposure and varying degrees of market integration.
Consistent with predictions, the researchers observed strong negative associations between PDS and biomarkers of viral and bacterial infection, and weaker associations between PDS and macroparasite infection. The latter appeared to be shaped by differences in market integration and the difficulty of avoiding soil-transmitted parasites during subsistence activities.
These results support the hypothesis that higher pathogen disgust sensitivity is associated with lower infection risk and demonstrate that disgust responses vary with local socioeconomic and ecological conditions, underscoring the role of evolved psychological mechanisms in human health outcomes.