When infections are high, humans avoid dissimilar others and will show preferences for obedience and conformity, according to the so-called Parasite Stress Theory. In the largest study to date, researchers decided to test this theory further and see whether the prevalence of infections can be related to citizen’s level of authoritarianism. Spoiler alert: it kind of does.

According to the analysis, areas with a greater prevalence of infectious diseases had more authoritarian citizens, who mainly voted conservatively and were governed by more authoritarian laws.

The researchers found that these patterns were present when studied not only between US states and metropolitan regions but also between different nations. Authoritarian attitudes were only related to infectious diseases that can be transmitted between humans and not ones that are transmitted between animals, which shows there’s a social mechanism at play here. 

Diseases and authoritarianism

“We find a consistent relationship between prevalence of infectious diseases and a psychological preference for conformity and hierarchical power structures – pillars of authoritarian politics,” study lead author Leor Zmigrod said in a statement. “Higher rates of infectious diseases predicted political attitudes and outcomes across geographical and historical levels.”

The researchers did an online survey to over 258,000 participants, most of them residing in the United States and a smaller group in other 46 countries. The data was collected between June 2017 and October 2018. The participants first had to complete a set of personality tests that were then followed by an authoritarian personality survey.

They were presented with four pairs of traits and were asked to indicate the quality that they believed is more important for a child to possess: “independent or respectful”; “obedient or self-reliant,” “well-behaved or considerate,” and “well-mannered or curious.”  This measure has been widely used in social and political psychology.

The researchers then used measures established by previous studies to calculate rates of infectious diseases and history pathogen prevalence. For the United States metropolitan regions, they calculated chlamydia and gonorrhea cases per 100,000 people, while for US states they quantified pathogen prevalence of all infectious diseases.

American woes

The most authoritarian US states had rates of infectious diseases four times higher than the least authoritarian states. Higher regional infection rates in the US also meant more votes for former president Donald Trump in the 2016 US Presidential Election, as well as more “vertical” laws that disproportionally affect certain groups. 

“Psychological and political behavior is thus shaped specifically by socially-relevant infections, in which the behavioral immune system (BIS) can motivate individuals to avoid dissimilar others and hence prefer authoritarian power relations. Public and personal health can therefore have fundamental repercussions,” the researchers wrote. 

The study called for further research on the Covid-19 pandemic and its consequences on citizens’ psychology and politics. Pathogen rates from over 20 years ago were still relevant to recent political attitudes, a seen with the case of Trump in the US. If Covid-19 in fact increases the attraction of authoritarian politics, the effects could last for a long time, the researchers said. 

“At a time of heightened awareness of infectious diseases, the current findings are important reminders that public health and ecology can have ramifications for socio-political attitudes by shaping how citizens vote and are governed,” the researchers conclude.

The study was published in the journal of Social and Political Psychology.