The “behavioural immune system” can drive harsher moral judgement and may even contribute to xenophobia.
Most of us will never come into contact with these pathogens, and so we should have no need to protect ourselves from the infections – but the news stories about them may nevertheless be influencing our minds in surprising ways.
As I first described for the BBC in April 2020, we are hardwired with a “behavioural immune system” that can shape our psychology at the merest suggestion of illness. Reminders of infection can lead us to become more conformist and risk-averse, less open-minded towards those who break social norms. There are even signs that it can contribute to xenophobia.
A prehistoric protection from infection
The body’s immune system includes some incredible weapons to strike infection once a pathogen enters our bodies – from the macrophages that engulf pathogens to the B-cells and T-cells that create specialised antibodies that can provide us with later immunity. Activating this army requires a huge amount of our energy, however – leaving us depleted at the end of the illness.
We have therefore evolved a set of psychological responses – named the behavioural immune system by Mark Schaller at the University of British Columbia – that should reduce our contact with pathogens in the first place.
Its most basic mechanism is disgust; we naturally avoid anything that looks or smells like it might put us at risk of infection. It’s the reason we retch when we smell rotting food.
Alongside this visceral response, the behavioural immune system involves subtler mechanisms that ensure we follow social norms. This would have been important, since cultures would have typically evolved certain rules – such as the hygienic preparation of food, or the disposal of waste – to reduce the spread of diseases that were common in their area. And in times of an outbreak, it would have been especially important that people stick to those protocols.
As a result, reminders of illness can make us more conformist.
That’s the theory, at least – and a host of studies lend some support to the idea. In one experiment, Schaller asked participating students to vote on a proposed change to the school’s grading system. He found that they were far more likely to vote in line with other students’ opinions – a sign of conformity – if they had just recalled a time when they had been sick.
To prevent diseases from spreading between groups, our fear of contamination can also decrease our trust of outsiders
Scientists from the University of Hong Kong, meanwhile, asked participants to evaluate some modern art, alongside an indication of how other viewers had rated them. Once again, a reminder of infection just beforehand – this time from graphic pictures of open wounds and writhing maggots – encouraged them to follow the herd rather than coming to their own conclusion. Participants who viewed images of car or train accidents – distressing events that do not carry the threat of infection – did not show the same level of conformity.
To prevent diseases from spreading between groups, our fear of contamination can also decrease our trust of outsiders. Based on a series of studies in the US and Europe, Lene Aarøe at Aarhus University in Denmark and colleagues suggest that we “unconsciously tag immigrants as bearers of pathogens” – and their results suggest that it can have a real effect on people’s political opinions once their behavioural immune system is activated.
Pandemic psychology
Consider a survey of 685 Italians in April and May 2020. Giulia Fuochi at the University of Padova in Italy and colleagues found a significant correlation between people’s fears of the virus and their views of various minorities, including immigrants, drug-using adults and foreign nationals, by expressing a weaker sense of shared identity and destiny.
These findings from real-world surveys have not always replicated, however, which may not be so surprising. Unlike the carefully controlled laboratory experiments, studies that attempt to respond to news events are messy, and cannot fully account for the many issues that may have been influencing people’s political opinions at the same time.
The truth is that our behaviours will depend on a host of different factors: our education, our profession, our family, our friends, our personality, and an uncountable number of personal experiences that feed into our broader personalities and worldviews. That’s not to mention the whims of our moods.
The next time we read about a new disease outbreak, then, it’s certainly worth considering how the behavioural immune system might be sharpening our judgements of rule-breakers and outsiders – but it is unlikely to have the final say in our decisions.