News of disease outbreaks can warp our brains in strange and subtle ways ^⁠21%

7/3/2026, 10:00:00 AM

Topics: Behavioural Immune System, Disease Psychology, Social Psychology, Evolutionary Psychology

Keywords: Behavioural Immune System, Psychology, Disease, Infection, Fear, Conformity, Xenophobia, Moral Judgement

BS Summary: This article contains 31 faulty reasoning types, including Post Hoc (False Cause), Negativity Bias, and Appeal to Authority, with Confirmation Bias as the most egregious example at 26.8% saturation with 267 hits. Analysis detected 2,170 faulty-reasoning hits from 997 analyzed words, generating a BS Score of 35.4% and a BS Rank of ⁠21% (16,181 of 20,371 articles). This article is better (less manipulative) than 79.40% of the article peer group.

Confidence50%

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997 words

Disease and death are back in the headlines.

The Ebola outbreak in the Democratic Republic of Congo is currently outpacing response efforts, and concerns about hantavirus linger, as new patients test positive for the infection.

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.

Later studies have shown that we become harsher in our moral judgements following reminders of illness.

Participants were more likely to judge a couple harshly for having sex on the man's grandmother's bed, for instance.

From the perspective of the behavioural immune system, this tendency to police others' behaviours would have helped ensure that the group, as a whole, took the necessary precautions to contain an outbreak.

Pandemic psychology

If the theory of the behavioural immune system is true, you might have expected to see notable shifts in people's social attitudes during real-world outbreaks like Covid-19, with one review noting changes in "social trust, interpersonal wariness, xenophobia, moral vigilance and political ideology" during the worst months of the pandemic.

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.

Speakers

6speakers17%attributed speech828writer words

44 attributed words26% of attributed speech88% writer coverage

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News of disease outbreaks can warp our brains in strange and subtle ways ^⁠21%

Speakers

Giulia Fuochi

Analysis

Biases

Fallacies

Manipulations

News of disease outbreaks can warp our brains in strange and subtle ways ⁠21%

Speakers

Giulia Fuochi

Analysis

Biases

Fallacies

Manipulations

News of disease outbreaks can warp our brains in strange and subtle ways ^⁠21%