What makes a good rumour?

Rumours that the petrol blockades might be starting again spread faster than wildfire. And before long, the queues returned to petrol stations. Why was this rumour so effective?

Commercial radio DJs may wish for power and influence. Some may even believe they have it.

But they can all bow to Warren Moore, the drivetime presenter on Cardiff's Red Dragon FM, who has been credited with starting the rumour that the petrol blockades were back on.

"A cocoa drought, daddy! The radio said so!"

Within hours, the rumour had spread around the UK, as motorists rushed to fill up again. Quite an achievement but the rumour was untrue.

So what made it so plausible? One might be tempted to suggest that:

Successful rumour = believability/originality +fear +status x contacts

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Believability

One obvious advantage was the fuel rumour had that ring of truth.

With Chancellor Gordon Brown saying he would not be forced into negotiating over cutting fuel tax, were people gullible to believe the protesters would be angered enough to reinstate their blockade?

Many people were caught unawares by the initial blockade, thinking that sort of thing only happened in France. They were wrong and may have suspended their original scepticism.

Originality

"A shortage of air fresheners? Quick, to the garage!"

People are not stupid. They might fall for a line once or twice, perhaps even three times.

That said, few days go by without millions of people falling for hoax warnings of a "dangerous new virus, for which there is no cure". This is despite the e-mails invariably being phrased in near identical terms.

Fear

Fear will cut through any amount of idle banter DJs might generate. Indeed, the fuel comment made by Red Dragon's Warren Moore was noticed because it appealed to fear.

Paul Marsden is an evolutionary psychologist whose consultancy - Brand Genetics - helps business create "contagious" products and ideas. He says our brains are overloaded with information we encounter in everyday life.

"In evolutionary terms our minds are still more suited to the savannah than the supermarket."

Rather be in the savannah?

So in the modern world, anything which corresponds to the crucial things in life, such as sex appeal, status or survival, will "cut through the data fog and capture our attention".

And what adds to Mondeo Man's sex appeal, status and survival? Petrol. QED.

The bogus e-mail warnings of a link between anti-perspirant and breast cancer which circulated in 1999 appealed to a more potent fear.

The warning claimed that anti-perspirant stopped toxins being purged through the armpits, and the build-up of them led to cancer. It might sound plausible but it is untrue.

The American Cancer Society's website felt compelled to reassure people that there was no scientific evidence for the claim.

Status

Being the first person to warn all your friends of something really nasty, or funny, or salacious, or dangerous puts you in a stronger position than them.

"What?!? Elvis alive on the Moon?"

Paul Marsden says: "Humans are inveterate copiers - we very rarely design an idea of our own. We are keen to be seen with an idea as we feel it increases our status."

Originating something that has "wow" factor for your pals can be gratifying, as well as bolstering your sense of importance.

Contacts

Technology has changed the rumour business, says Mr Marsden.

"Mobile phones and the internet have totally restructured our communication networks. Rumours once built up slowly and steadily, now they can spread like an epidemic."

Some people have better e-mail address books

He says rumours can spread particularly quickly through people who are "socially promiscuous" - ie those who know a lot of people.

Firstly, obviously, because they have better contacts books, and more e-mail addresses. And secondly because "these people also have a higher degree of perceived status". In other words, they tend to be opinion makers and are more likely to be believed.

So perhaps the adage of the 21st century rumour mill should be: "It's not what you know, it's who you hear it from."