Some may start life as pranks – ‘how many people can we get to believe that the Earth is flat?’ – but groundless conspiracy theories can do much real-world harm.

Xenophobic or racist ‘great replacement’ theories have been especially violent and dramatic, inspiring the massacres at Christchurch, Utøya and El Paso, while denialist theories (climate change or Covid-19) claim a slower toll.

It’s not easy countering, with accurate factual information, people who are spouting conspiracy theories. But it seems like the right thing to do. And it can work, in some cases. However, it can also backfire and reinforce the conspiratorial view, especially when the person concerned identifies closely with a conspiracy theory and its worldview. ‘To challenge the theory is to shatter the self-image of the person you are attempting to persuade,’ explains Michael Butter in The Nature of Conspiracy Theories.

Asking questions and using rhetorical devices that shift the focus onto the tricks of persuasion used by those who are spreading misinformation may stand a better chance. ‘People seem receptive to the ways in which they may have been manipulated,’ according to Cambridge researcher Sander van der Linden.

Pointing out logical inconsistencies may help. In social psychology experiments, adherents of conspiracy theories who were given a task that provided them with analytical tools were able to engage more objectively than those who were not. Many conspiracy theories rely on coincidences (‘5G masts appearing at the same time as coronavirus’) but a coincidence is not a covert operation. Also, theories (‘9/11 was an inside job’) often assume a superhuman degree of co-ordination and efficiency across a wide array of organizations and a Carmelite ability to keep quiet.

Prominent conspiracy theorists may identify as scientists or expert academics; some may be, but not in the area on which they are pontificating. It’s worth checking their bona fides online. Conspiracy is a lucrative business for many, via books (ex-family doctor and anti-vaxxer Vernon Coleman) or the mass media (US radio-host Alex Jones) and increasingly via social media (QAnon), where sources of funding and revenue are hidden.

So, what do the consumers get? Feelings of certainty in times of great uncertainty; someone to blame, says leading social psychologist Viren Swami. And ‘a sense of agency at a time when they lack control’. But rather than decreasing uncertainty and powerlessness, research suggests that conspiracy theories actually increase it. ‘They feel worse because it feeds into their fear,’ explains professor of social psychology Karen Douglas.

Finally, it’s worth remembering that some conspiracies do turn out to be real (Watergate, for example) and acknowledging this may be a gateway to a genuine, respectful two-way discussion. What’s least likely to persuade a conspiracy theorist to think again is ridicule.