OPINION: How will the Ebola crisis influence next week’s mid-term elections in the USA? One might expect that an epidemic limited almost entirely to West Africa should be way, way down on the list of factors likely to swing American voters. What with ISIS, the economy, Obamacare, abortion and so many other issues of greater direct relevance to the United States.

But a spectacularly scary hemorrhagic fever outbreak – ravaging countries a mere single plane flight from the USA! – holds the potential to propel a rightward swing next Tuesday.

I’ve written here before about the link between political conservatism, squeamishness about germs and hygiene, and something called the Behavioural Immune System (BIS).

Psychologist Mark Schaller proposed that certain behaviours enable us to gauge the risk of infection and take action to avoid becoming infected with whatever diseases currently prevail. He called these traits the Behavioural Immune System (BIS), a suite of psychological adaptations that reduce our chances of infectious disease. Because such diseases have killed so many people throughout history, our ancestors probably reaped huge fitness returns from traits - even subtle ones - that maintain hygiene and a tendency to avoid others who may be infectious.

What kinds of traits compromise the BIS? Disgust, for one. The kind of disgust we feel when we see or smell unsanitary conditions, food, animals and other people. A general distrust of strangers, however unsalutary, may have served our ancestors well. For most of history our ancestors lived in small groups where everyone knew each other, and new infections came mostly from animals or from outsiders.

So what does this have to do with politics? As I wrote in that earlier piece:

The tendencies to adhere to tradition, submit to authority and conform to hierarchy are all part of the socially conservative repertoire. As is a strong tendency to act unwelcomingly or aggressively toward out-group members. All of these behaviours promote in-group cohesion and negativity toward out-group members. Exactly the kinds of behaviours, then, that would minimise the risks of infection during an epidemic.

In the few short years since Schaller first mooted the idea of the Behavioural Immune System, studies claiming all manner of links between the BIS and conservative impulses have cropped up. Disgust, it seems, is an important component of the mistrust that right-wing authoritarians show toward foreigners and the profound ease that religious conservatives feel toward homosexuals and transsexuals.

Look at the brain

The links between political conservatism, disgust and outgroup mistrust, while far from iron-clad or deterministic, are nonetheless consistent enough to be reasonably well-established. At least among those who understand that humans are biological entities whose behaviours are shaped by complex interactions between environment and the biologic matter of our brains.

A brand-new study provides some new insights into how environmental cues of pathogen prevalence interact with the biological matter of our brains to shape political attitudes. The paper was supposed to be embargoed until the early hours of tomorrow, but proved just-too-hot for some media outlets. Woo-Young Ahn and P. Read Montague from Virgina Tech and their team extend research on disgust and political inclination into the colourful world of neuro-imaging.

The researchers presented subjects with a range of pictures known to evoke feelings such as disgust, threat, pleasantness or neutral feelings. They asked subjects to rate each image for the pleasantness, threat and disgust they evoked. They also mapped how their brains responded to image presentation, using functional Magnetic Resonance Imaging (fMRI). And last, after liberating subjects from the fMRI machine, they administered a questionnaire that mapped various dimensions of their political ideology.

Their findings:

Disgusting images, especially those related to animal-reminder disgust (e.g., mutilated body), generate neural responses that are highly predictive of political orientation even though these neural predictors do not agree with participants’ conscious rating of the stimuli. Images from other affective categories do not support such predictions. Remarkably, brain responses to a single disgusting stimulus were sufficient to make accurate predictions about an individual subject’s political ideology.

I’m no expert on fMRI images and their analysis, and I can guarantee this headline-grabbing result will flush out the neurosceptical who will, quite rightly, dissect it. But I’m intrigued by the finding that fMRI images of responses to disgusting images, but not other images, can predict political attitudes. For now, let’s score that as another piece of evidence in favour of the behavioural immune system.

The election

The number of people in the USA who have been infected with Ebola can be counted on one hand. And yet, the impact on the national psyche can scarcely be underestimated. The true epidemic, at least according to HuffPo’s Dean Baker, is Ebola Hysteria Fever.

Ebola hysteria seems to have infected somewhere close to 300 million. There are reports of kids being pulled out of schools and even some school closings. People in many areas are not going to work and others are driving cars rather than taking mass transit because they fear catching Ebola from fellow passengers. There are also reports of people staying away from stores, restaurants, and other public places in order to avoid the deadly plague.

I’m hardly the first to suggest that the current Ebola panic provides an absolute gift for US Republicans, as it does for those conservatives here in Australia who combine hair-trigger disgust sensitivity with xenophobia. Michael Gerson at RealClearPolitics reckons:

Some of our Ebola obsession … is manufactured for political reasons. A few conservatives - reaching for whatever stick lies handy in the immigration debate - have raised the prospect of Ebola-infected illegal immigrants crossing our porous southern border. The Centers for Disease Control and Prevention and Prevention (CDC) finds this prospect remote. It is, in fact, fantastical and malicious.

Frank Schaeffer, writing at Patheos, points out how perfectly is Ebola fuelling the toxic blend of racism and religious fanaticism that motivates the US far-right, particularly those who not only believe in the end-times but would welcome the apocalypse. Their enthusiasm for the second-coming tends to be wrapped up in an obsession with homosexuality and promiscuity (and their deity’s impending judgement - perhaps of a hemorrhagic nature), mind-warping hatred for President Obama, border control, racism and all forms of outgroup mistrust etc etc etc.

If disgust sensitivity and outgroup fear are components of our evolved behavioural immune system, then this brand of cynical right-wing tribalism would appear to constitute the metaphoric equivalent of an auto-immune disease.

Exactly how the Ebola crisis will weigh in the deliberations of US voters, and how it will stack up against other issues next Tuesday remains unknown. Perhaps exit polling will tell us something about that. But what interests me more is how images and words about the outbreak might stimulate voters' disgust sensitivity and fear of strangers, resulting in a swing that happens beneath the voters' conscious thoughts.

If the conservative press wants to flush out the right-wing vote, perhaps they should scale back political coverage and get those stories of hemorrhaging West Africans back on high rotation. But then again, if they overdo it then maybe those voters will be more likely to stay home to avoid infection?

Rob Brooks is Professor of Evolutionary Ecology; Director, Evolution & Ecology Research Centre at UNSW.

This opinion piece was first published in The Conversation.