Persuasion is a science

There's a proven formula for getting people to do what you want them to do - and politicians would b

For as long as I can remember, newspaper managements have issued circulars demanding that journalists claim fewer expenses. Hacks are to take contacts to lunch only once a week or claim taxis home only after public transport has stopped. The pleas invariably fail. Why? Because some journalists would previously claim fewer than one lunch a week or never think of taking a taxi home. Now, aware that others claim these perks, they will do likewise. Managements thus normalise the behaviour they want to discourage.

Politicians and other public figures often fall into the same trap. I would be surprised if there were not a sharp rise in teenagers carrying guns in south London, and perhaps in other urban areas, following this month's decision to put armed officers on the streets and to hold a "crisis summit". Ministers and police make guns seem normal in Clapham, and so any male teenager lacking one will be tempted to arm himself quickly. I suspect similar things happened, over many years, with drugs and teenage pregnancies. I accept the media's role: if ministers failed to act after three fatal shootings in rapid succession, they would be condemned for complacency. But it is striking how rarely politicians think outside this box.

Perhaps Robert Cialdini can help them. Cialdini is a psychology professor at Arizona State University, author of Influence: the psychology of persuasion, and the latest guru to appear on the new Labour scene as the party tries to remake itself after a decade in power. His book was first published more than 20 years ago, and the science of persuasion - a distillation of techniques long used by car salesmen, advertising copywriters and lobbyists - is nearly 60 years old. Moreover, he has "six universal principles" (all American academics, I sometimes think, at heart want to be Billy Graham) and a company offering training and consultancy to business, which suggests he could sell snake oil if he were minded to. Still, he gives research references and precise statistics. He has apparently struck a chord with new Labour and attended a Downing Street seminar last month.

I do not have space for all six principles which, Cialdini says, are behind every successful attempt "to motivate people into action". So, here are two. First, social proof: we are most likely to behave in a particular way if we believe people like ourselves are doing the same.

This supports my examples of journalists and south London teenagers. It also explains why an anti-litter ad showing one person dropping an empty crisp packet in a pristine landscape works better than an ad showing thousands of dropped packets: the latter makes dropping litter look normal.

And the best way to get hotel guests to recycle linen, Cialdini says, is not to put up a notice explaining environmental benefits, but to say that "the majority of guests who have stayed in this hotel" have already done it. Better still, make the notice refer to "guests who have stayed in this room". Cialdini emphasises that such improvements are "costless". One sees the appeal to new Labour.

Second, authority: we are more likely to follow a proposal from someone who seems both expert and trustworthy. So it really is worth putting initials after your name and Dr in front of it. Equally, you create trust by conceding a weakness in your case immediately before (not after) you explain its strongest points. "By mentioning a downside, you establish yourself as a credible source of information."

Cialdini said in a lecture at the Royal Society of Arts (RSA) this month: "People then listen differently to the next thing you say. They open their ears and minds." So, when recommending someone for a job, mention a weak spot before you rhapsodise about their brilliance.

We can see again where politicians may be going wrong. They rarely admit a weakness at all. If they do, it's called a gaffe.

Pro-social behaviour

Matthew Taylor, the RSA chief executive and former (but still influential) Downing Street policy wonk, has drawn on Cialdini's work to form the idea of "pro-social behaviour", the opposite of antisocial behaviour. He compares politicians to Mark Twain's man with a hammer, to whom everything looked like a nail. They believe all social problems are susceptible to their most accessible tools: laws, regulations and taxes. They should look instead, Taylor says, at Cialdini's principles, which can be used to strengthen desirable social norms (see acrobat/pro-social_behaviour.pdf).

Clearly, a government that managed to create huge opposition to road-pricing at the moment everybody seemed convinced of global warming needs to think hard about how it does things. The Cialdini and Taylor approach, of quietly encouraging change in public behaviour before trying to regulate it, looks promising. Unfortunately, the image of the nail-obsessed hammer-wielder reminds me of someone. Now, who could it be?

Peter Wilby was editor of the Independent on Sunday from 1995 to 1996 and of the New Statesman from 1998 to 2005. He writes the weekly First Thoughts column for the NS.