The coronavirus disease 2019 (COVID-19) pandemic is by no means the first pathogen scare faced by humans. As Homo sapiens disperse across different geographical regions and encounters new animal species or other conspecific groups, our ancestors were inevitably exposed to novel pathogens against which they have no physiological immunity. As a result, behavioral and psychological mechanisms have evolved to mitigate personal infection risks and to facilitate collective efforts to contain the spread of diseases ( Fincher & Thornhill, 2012; Murray, Schaller, & Suedford, 2013; Murray, Trudeau, & Schaller, 2011; Schaller & Park, 2011). These instinctive “behavioral immune responses”, nevertheless, have undesirable side effects in modern, heterogeneous societies. For example, people might resort to a conservative or discriminative mindset (e.g., traditionalism and xenophobia), which, in evolutionary history, functions to minimize contacts with outsiders who might spread novel pathogens ( Faulkner, Schaller, Park, & Duncan, 2004; Tybur et al., 2016). This is particularly relevant during the ongoing COVID-19 crisis, as incidents of outgroup prejudice targeting a variety of victims at individual, societal, and political levels are drawing increasing attention ( Clissold, Nylander, Watson, & Ventriglio, 2020; Roberto, Johnson, & Rauhaus, 2020). As the United Nations Secretary-General Antonio Guterres tweeted, “[the pandemic] unleash a tsunami of hate and xenophobia, scapegoating and scare-mongering” ( Guterres, 2020).
2. Pathogen Prevalence and Collectivistic Norms
Humans have a long history of coevolving with many kinds of pathogens that cause infectious diseases due to group living and animal husbandry ( Diamond, 1997). Pathogens, as a recurrent challenge in evolutionary history, were believed to be instrumental in shaping human behaviors and culture, leading to a “behavioral immune system” ( Murray & Schaller, 2012; Schaller & Park, 2011). This includes individual-level behavioral proclivities such as heightened risk aversion and social tendencies such as obedience, conformity, and compliance with social norms ( Schaller & Murray, 2008; Wu & Chang, 2012). The latter aspect was strongly associated with collectivistic cultural norms (rules and expectations shared by people to ensure collective interests; Chen, Wasti, & Triandis, 2007), thus leading to the speculation that pathogen prevalence might constitute one of the environmental facilitators of collectivism and authoritarian social structures ( Chang, Mak, Li, Wu, Chen, & Lu, 2011; Fincher, Thornhill, Murray, & Schaller, 2008; Murray et al., 2013).
According to an epidemiological index compiled by Murray and Schaller (2010), which documented the historical prevalence of nine diseases across 230 geographical regions, Asia (M = 0.49, SD = 0.38) had a much higher pathogen load than Europe (M = −0.43; SD = 0.39). These historical pathogenic stress levels seem to correspond closely with cultural patterns in terms of collectivism-individualism. Teaching and parenting in East Asian societies heavily emphasize obedience, uniformity, rote learning, and modesty at the cost of autonomy, whereas Western societies (mostly in Europe and North America) emphasize individuation, creativity, and expression ( Chang et al., 2011; Zhu & Chang, 2019). Research has also found societal-level correlations between historic pathogen prevalence and emphases on family ties, behavioral conformity, and compliance with social norms, all of which commonly linked to collectivism ( Cashdan & Steele, 2013; Fincher & Thornhill, 2012; Fincher, Thornhill, Murray, & Schaller, 2008; Murray & Schaller, 2012; Murray, Trudeau, & Schaller, 2011). Fincher and Thornhill (2012)’s research showed that pathogen prevalence in both contemporary and historical times is associated with stronger family ties and religiosity. Cashdan and Steele (2013) found that traditional societies facing high pathogen stress were more likely to socialize children toward collectivist values centered on social learning and interdependence (obedience rather than self-reliance). Importantly, there is little evidence suggesting that collectivistic cultural practices have to do with increased pathogen exposure (the opposite seems to be true; Cashdan & Steele, 2013).
Finally, collectivistic norms that enforce ritualized behavioral practices have historically served disease-control functions (reviewed in Fabrega Jr., 1997) and might be seen as a society-level behavioral immune system. Empirical evidence has revealed that infection risks are conducive to collectivistic norms, causing individuals to prefer conformity and obedience in others and to respond more negatively toward others who fail to conform ( Murray & Schaller, 2012; Wu & Chang, 2012). Additionally, authoritarian forms of governance that enforce collective norms and punish individuals deviating from these behavioral traditions might be accepted to a greater degree in regions historically faced greater parasite stress. This is supported by cross-national covariation between pathogens and authoritarian personalities, and the link between pathogen prevalence and authoritarian governance among traditional societies ( Murray et al., 2013).
3. Pathogen Prevalence and Outgroup Prejudice
According to the parasite stress theory, contacts with members of other groups may introduce potentially deadly pathogens, which hurt the evolutionary fitness of ingroups as they have no immunity to and no knowledge of the novel pathogens. This leads to the speculation that pathogen threats would contribute to outgroup prejudice and xenophobic attitudes ( Faulkner et al., 2004). History is replete with anecdotal examples of scapegoating, stigmatization, and xenophobia during and following disease outbreaks. During the height of the black death plague in 14th century Europe, Jewish citizens were blamed for the spread of the plague and accused of “poisoning” water supplies ( Markel, 1999). The Chinese Exclusion Act of 1882 was enacted following a smallpox outbreak in San Francisco ( Parmet, 2007). More recent examples included outgroup-disfavoring biases following the avian influenza outbreak from 2005 to 2007 ( Gilles et al., 2013), the anti-Africa racism in European countries after the Ebola scare in 2014 ( Prati & Pietrantoni, 2016), and xenophobia in the ongoing COVID-19 pandemic (e.g., Sorokowski et al., 2020; Vachuska, 2020). Sometimes, prejudice against outgroups associated with infection risks was activated even before the first case of infection in the country ( Rzymski & Nowicki, 2020). None of these examples, however, establish a long-term link between outgroup prejudice and chronic pathogen prevalence in these regions, which is necessary for the evolution of outgroup-avoiding behavioral immune responses.
Outgroup avoidance as a behavioral immune response might stem from deep-rooted physiological and emotional reactions (disgust) that drive disease-aversive behaviors ( Schaller & Park, 2011). Research on the “source effect” should that individuals exhibit greater automatic disgust reactions to malodors of strangers than to those of oneself and familiar others ( Peng, Chang, & Zhou, 2013; Stevenson & Repacholi, 2005). Nevertheless, it is problematic to assume that the threat of diseases invariantly engenders outgroup prejudice. Other experimental studies have shown that not all outgroups are associated with disease-related disgust emotions ( Cottrell & Neuberg, 2005) and that the link between pathogens and outgroup prejudice is contingent on individuals’ sensitivity or vulnerability to disease infection ( Faulkner et al., 2004; Huang, Sedlovskaya, Ackerman, & Bargh, 2011; Klavina, Buunk, & Pollet, 2011; Navarrete & Fessler, 2006; O’Shea, Watson, Brown, & Fincher, 2020). Moreover, superficial physical features such as physical deformity and obesity also trigger prejudicial reactions because of their evolutionary connection to diseases, even though people with these features are “ingroups” ( Schaller & Neuberg, 2012).
Findings regarding the purported link between pathogens and ingroup-outgroup biases are not consistent at the cross-society level. For instance, a large-scale 30-nation study ( Tybur et al., 2016) found that national parasite stress correlated with higher traditionalism (i.e., adherence to group norms) but not higher social dominance orientation (i.e., endorsements of intergroup barriers and discrimination against ethnic and racial outgroups). Cashdan and Steele (2013) found no association between pathogens and ingroup-outgroup biases (e.g., xenophobia) using the Standard Cross-Cultural Sample of 186 traditional societies. Recent studies that controlling for factors such as government services and material security also found no evidence for ingroup-outgroup biases in societies with higher pathogen stress ( Hruschka et al., 2014; Hruschka & Henrich, 2013; Romano, Balliet, Yamagishi, & Liu, 2017). Additionally, Tybur et al. (2015) provided evidence that correlations between the degree of outgroup prejudice (measured as social conservatism) and pathogen avoidance motivations can be accounted for by the co-variation between disgust sensitivity and sociosexual orientation. All these findings cast doubt on the assumption that pathogen threats would always motivate negative perceptions of outgroups as a behavioral immune response.
4. Distinction between Collectivistic Norms and Outgroup Prejudice
To better understand the relationship between parasite stress and outgroup prejudice, it is important to distinguish between ingroup positivity and outgroup prejudice ( Brewer, 1999, 2007). Ingroup-outgroup distinction is not specific to any cultural orientation but underlies group functioning in all human societies ( Brewer & Chen, 2007; Brewer & Yuki, 2007). Results from both experiments and field studies indicate that favorable attitudes toward ingroups do not correlate with bias or negativity toward outgroups ( Yamagishi, Jin, & Miller, 1998; Reviewed in Brewer, 1999, 2007). Research using minimal group procedures, for instance, generally found that individuals are willing to favor ingroups but are reluctant to directly harm outgroups (e.g., Mummendey et al., 1992; Cameron, Alvarez, Ruble, & Fuligni, 2001). East Asians living in collectivistic societies were found to be less discriminative against outgroups in minimal-group settings when such behaviors do not manifestly benefit ingroups ( Yamagishi et al. 1998). Overall, we can infer that collectivistic norms that emphasize ingroup positivity do not necessarily bring about intergroup antagonism and divisiveness.
On the contrary, collectivistic norms and the relevant suite of psychological adaptations (e.g., respect of rules and authorities) comprise the cornerstone of large-scale cooperation ( Chudek & Henrich, 2011). This is supported by previous research showing that allocentric (collective-minded) individuals acted more cooperatively when there were cooperative norms than there were not. By contrast, idiocentric (individualistic) individuals were not only more focused on self-interests at the expense of the group but also less sensitive to cooperative norms ( Chen et al., 2007). Many aspects of collectivism appear to promote large-scale cooperation among people facing the same environmental challenges, such as irrigation projects required by rice-farming ( Talhelm et al., 2014) and unmitigated climatic challenges because of the scarcity of economic resources ( Van de Vliert, Yang, Wang, & Ren, 2013). This also applies to the threat of pathogens. Societal preventive measures against communicable diseases necessitate collective efforts organized by central, collective authorities ( Murray et al., 2013).
Moreover, outgroup prejudice entails additional costs of foregoing mutually beneficial cooperation opportunities with outgroups (e.g., trade, exchange of knowledge and information, and intergroup mating) and might be counterproductive even in early human society ( Zhu, Lu, & Chang, 2020). Thus, from an evolutionary perspective, outgroup prejudice and distrust should only be invoked when the fitness costs of disease infections outweigh fitness gains from interaction with outgroups.
5. Collectivistic Norms Reduces Divisiveness in the Face of Disease Threats: A Hypothesis
For humans, cultural rituals (e.g., related to hygiene, food processing, and social etiquette) have historically served to minimize infection risks ( Fabrega Jr., 1997). Although norms and rituals as non-pharmaceutical disease-control efforts are not always effective in the fight against diseases, they are essential to maintain intragroup and intergroup cooperation during epidemics and pandemics, especially when there are no medical solutions for the pathogens. Although the tradeoff between avoidance of infection and intergroup cooperation applies to all cultures, differences in cultural norms derived from historical pathogen prevalence might predict different attitudes and behavioral adjustments in the face of the same pathogen threat. In environments with high pathogen prevalence, strong collectivistic norms enforced by authorities might serve to ensure people’s adherence to these rules and rituals for the greater good of public health, thus contributing to disease control ( Murray et al., 2013). Knowing others are following the same rules and rituals that serve collective interests might relieve worries about communicable diseases, thus causing people to be less prone to resort to outgroup prejudice as a behavioral immune response in collectivistic societies. It is conceivable that disease-prevention interventions and norms that necessitate temporary sacrifices of personal choice and freedoms for the greater good of public health (e.g., quarantines, community closures) might face more psychological backlash in individualistic societies ( Zhu, O, Lu, & Chang, 2020), which historically faced lower pathogen stress ( Murray & Schaller, 2010). Emerging evidence indeed did show that collectivism is associated with better psychological adjustment in the face of the COVID-19 pandemic and accompanying societal regulations among young adults ( Germani, Buratta, Delvecchio, & Mazzeschi, 2020).
Further, collectivistic norms and collective authorities might serve as social glues that bind people together in the face of common threats of infectious diseases, essentially mitigating intergroup tensions and maintain large-scale cooperation. Collectivistic cultures emphasize social-learning strategies such as conformity (i.e., preferentially copying the most widely accepted solution or following the majority) and compliance (i.e., preferentially copying high-prestige models or following leaders; Boyd & Richerson, 2005). Such conformist and prestige biases ( Boyd & Richerson, 2005) should allow central authorities in collectivistic societies to mobilize the public and maintain social order despite the implementation of drastic societal preventive measures after disease outbreaks. For instance, within a few weeks after the initial report of the outbreak in Wuhan, thousands of medical staff and health professionals from all overall China were deployed to Hubei (the initial epicenter of the pandemic) to help the local hospitals fight against the COVID-19 threat ( The Star, 2020). Such concentrated efforts organized by the central authority boosted inter-province cooperation and essentially mitigated the possibility of regional discrimination and stigmatization of people from provinces most affected by COVID-19 outbreaks. Ultimately, collectivistic norms, by maintaining cooperation and rooting out prejudice, can be seen as an extension of the behavioral immune system that not only reduces infection risks but also enhances societal members’ fitness via increasing cooperative opportunities in high-pathogen environments. More empirical research is needed to test this postulation, but it carries profound implications for public health policymaking during the current COVID-19 pandemic.
The same disease threats might undermine intergroup cooperation in individualistic societies that historically faced lower parasite stress ( Murray & Schaller, 2010) and thus, are reluctant to adopt collectivistic norms. Recent empirical evidence indicated that racial prejudice and xenophobia are likely to rise in predominantly individualistic societies (e.g., Poland, the United Kingdom, and the United States) during pandemics ( Croucher, Nguyen, & Rahmani, 2020; Rzymski & Nowicki, 2020; Sorokowski et al., 2020; Tabri, Hollingshead, & Wohl, 2020; Vachuska, 2020). More relevantly, a study informed by the pathogen-prevalence hypothesis showed that the association between xenophobic attitudes and increased vulnerability was especially pronounced among people scoring high in individualism and low in collectivism ( Kim, Sherman, & Updegraff, 2016).
Outgroup prejudice as a side effect of the common behavioral immune system may be more common in individualistic societies, where there are pre-existing prejudices associating outgroups to diseases and pathogens ( Clissold et al., 2020; Roberto et al., 2020). Individualistic cultures, which typically emphasize autonomy, independence, and nonconformity ( Kim & Markus, 1999; Talhelm et al., 2014) tend to emphasize independent solutions and trust in individuals, not authorities and norms ( Chang et al., 2011; Yamagishi et al., 1998). Without a central authority to maintain cooperation beyond immediate ingroups, individuals might easily justify pre-existing outgroup prejudice by associating outgroups with infection risks (even when there is no epidemiological link), especially when they experience high levels of anxiety and threats. This is supported by recent research ( Tabri et al., 2020), which showed that framing COVID-19 as an existential threat, compared with framing it as non-threat, increased American participants’ anxiety, which, in turn, predicted heightened prejudice against outgroups purportedly linked to infection risks (Chinese people).
In summary, there is considerable empirical evidence linking pathogen prevalence to collectivism. However, the collectivistic norm that benefits ingroups do not necessarily indicate outgroup discrimination. Outgroup prejudice as an undesirable side effect of behavioral immune systems might be more common in individualistic societies that lack a centralized disease-prevention effort. One reason for this might be that collectivistic norms derived from high-pathogen environments not only serve to reduce infection risks but also constitutes a social mechanism to maintain cooperation and mitigate discrimination in the face of pathogen threats. To conclude, understanding how cultural and social structural factors affect the manifestation of different behavioral immune responses is particularly relevant during the current COVID-19 pandemic. While it is human nature to fear infections from other people, this does not mean we cannot maintain social cooperation and inclusion during a pandemic. After all, division and fear of others will only lead to worse outcomes for all, and cooperation and solidarity are the ultimate “medicine” for a pandemic.
The authors declare that they have no conflict of interest and received no funding when submitting this paper.
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