Your political views could be shaped by a parasitic infection called toxoplasmosis, a new study has found. Toxoplasma gondii is one of the world's most common parasites, mainly contracted by humans through contact with cats that are infected, as well as by eating foods (especially lamb, pork and venison) that are contaminated with the parasite. It's estimated that around a third of the population is infected.
"Humans infected by Toxoplasma gondii express no specific symptoms but manifest higher incidence of many diseases, disorders and differences in personality and behavior," the team wrote in their study, published in Evolutionary Psychology. "The aim of this study was to compare the political beliefs and values of Toxoplasma-infected and Toxoplasma-free participants."
The team used a survey to measure the political beliefs of 2,315 people, 477 of whom were infected with Toxoplasma, controlling for factors like age, sex, and the area in which they lived. Compared to the control group, people who had toxoplasmosis were generally found to score higher in tribalism, and lower in cultural liberalism and anti-authoritarianism than their non-infected peers.
There were differences between men and women participants, with men infected with Toxoplasma showing a slight negative association with tribalism, as well as an increased preference for economic equity and a less competitive society, something which the researchers were not expecting. Infected women, meanwhile, scored higher in tribalism and lower in cultural liberalism. Both men and women with toxoplasmosis have previously been found to score lower for conscientiousness and generosity.
The team speculated that the differences in political beliefs could be attributed to worse physical health (shown in both infected men and women) and worse mental health (mainly found in infected women). However, when they controlled for these factors the associations were not reduced, "suggesting that impaired health of infected subjects is not the cause of changes in political beliefs," the authors write. "The same conclusion was also supported by the fact that the changes go in the same direction in men and women, because stress coping-associated behavioral and personality changes mostly go in different directions in men and women".
The team offered a few possible explanations for the change, including that differences might be due to having a long-term mild inflammatory reaction because of the parasites.
"While the direction of causality needs to be studied further and while the human-centred field of parasite induced changes in personality traits is regrettably understudied and quite complex, we might expect at least some effect of infectious diseases on political attitudes caused by shifts of personality traits," the authors write in their discussion. Given the prevalence of the disease, it could theoretically have an impact on political climates in countries with high levels of infection.
“Toxoplasma is a very widespread parasite, and therefore its prevalence (which varies dramatically between and within countries) can influence not only the political climate in different countries and different social strata of the population," study author Jaroslav Flegr told Psypost, "but also real-world politics and, consequently, history.”
The study is published in Evolutionary Psychology.