We like to think that our political beliefs are coherent and well thought out. We tend to believe we have arrived at them through serious moral and factual consideration. But what if it could be shown that rather than arriving at these beliefs through careful deliberation, we in fact come to them by way of deeply-rooted biological predispositions? What if reason, rather than being the mechanism by which we come to our political opinions, merely provides us with justifications for beliefs we were bound to have regardless?

Exactly this possibility is what researchers at Virginia Tech in the US explored in the mid-2000s when they studied the relationship between political orientation and physiological reactivity to threat. This team of neuroscientists looked at MRI scans of 83 peoples’ brains while they were shown a number of both emotionally evocative and neutral pictures. The emotionally evocative pictures included mutilated animals, people eating worms, and a screwdriver poking towards a human eyeball, while the neutral ones included a fruit bowl, and the inside of a room. After this, the participants were administered questionnaires asking about their views on important political and social issues. This enabled the researchers to place them on a spectrum from extremely liberal to extremely conservative.

To their surprise, the researchers found massive differences between the brains of liberals and conservatives when it came to their response to repulsive images. Both groups reacted to them, but these reactions involved different brain networks. This difference was so pronounced that it was possible to predict with 95% accuracy whether a participant was liberal or conservative. The researchers also noted that responses to disgusting imagery, like the person eating worms, was far more predictive of political orientation than violent imagery, like the screwdriver being driven into a person’s eye.

This difference was so pronounced that it was possible to predict with 95% accuracy whether a participant was liberal or conservative

These results have been backed up by a growing body of evidence suggesting that conservatives are more sensitive to threat than liberals. This evidence also points to a stronger correlation between disgust and political orientation, than violence and political orientation. As of yet, however, it is unclear whether this is because disgust is simply a more powerful and relevant emotion than fear in the political realm, or whether it’s simply easier to make somebody disgusted in a lab than it is to make them afraid.

So strong is the role of disgust sensitivity, political scientist Michael Bang Petersen points out, that it is at least as good a predictor of political orientation as education or income. The robustness of these results is further supported by the fact that similar findings have been observed in a number of different countries and cultures worldwide. In each of these contexts, it is always the same; higher disgust sensitivity is related to conservative political belief.

So, what could account for this link? Why would your reaction to pictures of mutilated animals or germy sponges be linked to your views on immigration or transgender rights? To answer this, researchers have coined the idea of a “behavioural immune system.” This immune system has the same function as our biochemical immune system (protecting us from pathogens), but it operates through behaviour instead of through the lymphatic and blood systems. The idea goes that when we encounter something which may cause infection or illness, like vomit or mouldy food, we feel revulsion, which causes us to move us away from the object of our disgust. Even the facial expression we make when we are disgusted – the eyes squinted, nose shrivelled, lips pressed together – this is designed to ensure that whatever is on the outside does not make its way into our bodies.

This immune system has the same function as our biochemical immune system (protecting us from pathogens), but it operates through behaviour instead of through the lymphatic and blood systems

Just to keep us on the safe side of things, evolution has made us overly-sensitive to disgust, leading us to be disgusted by things like obesity, liver spots, and various non-contagious deformities. These have no chance of hurting us, but on an evolutionary level, it simply pays to err on the side of caution. As the scientific literature on this has repeatedly shown, this fear of contamination extends all the way to people themselves. Specifically, this disgust is often felt towards foreigners. Some researchers think this link can be traced back to the fact that throughout history, foreigners would have been more likely to expose local populations to pathogens against which they had no defences (think Christopher Columbus and the Native Americans). Others believe that the link is less deeply-rooted, and that fears about germs simply piggyback on negative stereotypes about foreigners; that they are dirty, more sexually loose, and eat strange foods.  

This would seem to explain the relationship between views about immigration and disgust sensitivity quite easily. It’s also interesting to note that even the language used in these political discussions borrows heavily from language about disease and infection. Immigrants are often described as a “plague”, and their migration as an “invasion”. In Nazi Germany, Hitler spoke of the “vermin” that was the world’s ‘Jewry’ (he even used the same gas – Zyklon B – to exterminate the Jews, that he had previously used to rid German factories of rats after he became chancellor). He referred to Jews as “parasites” on German society, and as a virus which must be eradicated. It may thus be no coincidence that the man was a germophobe.

What then about issues like gay marriage and transgenderism? Can these too be squared with the findings of the so-called new science of “disgustology”? In one experiment, social psychologists Simone Schnall and Jonathan Haidt examined two groups with similar political stances. They exposed one group to a vomit-like scent as they filled out questionnaires assessing their social values, while the other group filled out the questionnaires in an odourless setting. Despite both groups having comparable political ideologies, those in the group exposed to the vomit smell showed more opposition to gay rights, pornography, and premarital sex than those in the second group. Other similar studies involving other methods of creating disgust, like bad tastes and sticky tables, have found the same result; when we feel disgusted, we make harsher moral judgements.

When we feel disgusted, we make harsher moral judgements.

None of this undermines the validity of conservative political opinions, it should be pointed out. It is just a matter of fact that sometimes the best solutions to political problems are conservative, and sometimes they are liberal. The two poles would not exist otherwise. The fact that conservatives are more prone to holding political opinions based on disgust does not mean that this less pronounced tendency among liberals is any more rational. The facts are what they are, and a mind led by disgust is no less likely to come to the “correct” conclusion about an issue than a mind less led by disgust. What this research shows is that either way, biology plays a bigger role in our politics than we would like to admit.