A "psychological vaccine" of a weakened form of a piece of fake news can make people better at identifying false claims about climate change, researchers have said.

Turning one of the main tactics of fake news back on itself is an effective strategy to halt the spread of misinformation, psychologists say in a study published in the journal Global Challenges.

Exposing people to a fake "fact" with either a general warning about fake news or a specific analysis of why a claim is false can help people to dismiss fake news stories on climate change, the study of 2,000 people in the US found.

Giving no inoculation – or presenting a scientifically sound fact and a fake "fact" together – cancelled out the effects of both statements and left people with exactly the same opinion as they had had before reading the statements.

The general or specific warning weakened the power of the fake claim. This strategy is called psychological inoculation, and is one that has historically been used to generate public uncertainty on issues such as the health risks of tobacco.

Eroding the evidence

The scientifically backed claim used in the study was that 97% of climate scientists agree that anthropogenic climate change was real. The false claim was that 31,000 US scientists had signed a petition stating that anthropogenic climate change was not real.

Just the scientific claim by itself made people 20% more likely to shift their view in favour of thinking climate change is real. Showing them just the fake "fact" made them 9% more likely to reject the idea of climate change.

If they were given these two statements one after the other, the fake claim cancelled out the evidence-based claim, leaving people exactly where they were before they had read the statements.

General vs targeted inoculation

Adding a general warning that "some politically motivated groups use misleading tactics to try to convince the public that there is a lot of disagreement among scientists" made people 6.5% more likely to change their view in favour of the scientifically backed claim when they saw the two together.

A specific inoculation debunking the statement about the petition was even more effective. Here people were told that many of the 31,000 signatories to the petition were fake, with names such as Charles Darwin and members of the Spice Girls cropping up. Of the signatories that were real, living scientists, fewer than 1% had a background in climate research.

This detailed debunking of the fake claim made people 13% more likely to shift their view in favour of the scientific claim after seeing the two together. That's still not back to the 20% shift seen when the scientific claim was made alone, but it did at least as much of the damage caused by the fake claim.

"It's useful to forewarn people generally because it makes them more cautious about the information that they encounter," study author Sander van der Linden of the University of Cambridge told IBTimes UK. "But if you arm people will actual arguments – because it's often the problem that people don't feel confident in their arguments – then that can help inoculate people against misinformation."

Beyond climate change

The idea of psychological inoculation is not a new one. It's been used historically by the tobacco industry to counter scientific evidence of the health risks associated with smoking. Industries such as this have had an "intuitive understanding" that questioning the idea of consensus is very persuasive, van der Linden said.

"Generally it's easy to create a sense of doubt in the public consciousness, that's essentially their strategy. Sow these seeds of doubt by pre-emptively telling people that there's a lot of disagreement among scientists on a given topic."

This is a general aspect of human cognition and can be applied to many areas besides climate change. For example, inoculation could have been used to moderate the effect of claims about Brexit before the UK's EU referendum, many of which lacked a foundation in fact, van der Linden said.

"When it comes to fake news and false information – whether in the UK, US or another part of the world – people use simple rules of thumb to accept information because we're not deeply thinking about it.

"If you think about Brexit, a lot of the information that circulated was not accurate or based on fact, but lots of people believed it because they weren't consciously engaging with the issue. Would it have been beneficial to try to inoculate people? Probably."