The Labour MP Keith Vaz and I are not Facebook friends. The fact that we don’t exchange Christmas cards is not simply because only one of us believes Jesus is the Messiah. And – how shall I put this delicately – I’ve read the entire Standards and Privileges Committee report on Mr Vaz’s business affairs.

So I take a deep breath before I say this – Gordon Brown should be paying closer attention to the advice of Mr Vaz.

Actually, not just Mr Vaz. The Prime Minister might also find it worthwhile listening to a couple of Nobel prize-winners, reading a history of Chinese psychological punishments and thinking about why he bothers to go out canvassing for votes.

And once he’s done all that, he should announce that he intends to hold a referendum on the new European treaty.

He should do it for the most hardheaded of reasons – it could prove his greatest-ever triumph.

The conventional view is that any European referendum will be lost by the advocates of greater integration. It is for this reason that Mr Brown doesn’t want to put the new treaty to a vote. Mr Vaz and other European enthusiasts who call for a ballot and think they might win are regarded as charmingly eccentric but quite without any political common sense.

There is a good deal of evidence to support this. Opinion polls traditionally record big majorities for the Eurosceptic side, whether it’s a new currency or a new treaty that is being asked about. But I think these polls are deceptive. Why? Because in a referendum campaign the “yes” side would hold in its hand what students of the science of influence regard as two of the most powerful weapons of persuasion.

Back in the 1970s the psychologist Thomas Moriarty tried an experiment on a New York beach. He left a radio on the sand to go swimming and then sent a “thief” to pinch it. In repeated instances of the “theft”, bystanders rarely intervened. Then he tried the experiment again, this time turning to a bystander and asking if they would watch his things, which they duly gave their word to do. This time, almost every bystander intervened to challenge the thief, either verbally or physically.

The explanation for this behaviour? The strong desire people have to remain consistent with their public pronouncements. The psychologist Robert Cialdini told a London audience recently of how a restaurant transformed its no-show policy. Instead of telling diners when they booked “Please be sure to call if you can’t make it”, they asked: “You will call if you can’t make it, won’t you?” The simple “yes” they got in response vastly increased compliance. Another example of the power of consistency.

During the Korean War, Chinese interrogators had their captives write down why they were disillusioned with the US and their positive feelings towards China. Gaining compliance for this was a remarkably effective way of getting much greater acts of collaboration from the same soldiers.

This principle is familiar to political activists. When they go canvassing, they ask householders whether they intend to vote for a particular party. In delivering a verbal offer of support, voters become more likely to attend and provide the support they committed themselves to give.

There have been few more impressive masters of the theory of consistency than Jean Monnet, the founder of the European Union. From the beginning he understood how small steps lead to bigger ones. He deliberately engaged European nations in limited economic projects that, once embarked upon, appeared to require further integration in order to work properly. The desire to remain consistent then propelled nations on, pulling them deeper and deeper into a superstate. There’s even an ugly Euopean bureaucratic word for this idea. Didn’t you just know there would be? Monnet’s strategy is known as neo-functionalism. I’m not sure why, but there you go.

In a referendum, supporters of the treaty would use our addiction to consistency to reel us in. We agreed to join in 1972, we’ll be told, and we can’t be half in, half out. We must be full members, not waiting on the sidelines. We enlarged the EU, the argument will run, and no one much objected. This treaty is just the logical next step – it simply puts in place the institutional framework to manage the changes that we’ve all already agreed to. We’re committed already; we need to remain consistent.

Alongside consistency, the supporters of a “yes” vote will be able to rely on an allied tendency – loss aversion. The economists Amos Tversky and Daniel Kahneman won the Nobel prize for their work on people’s attitude to risk. They demonstrated convincingly that aversion to making a loss figured far more strongly in people’s calculations than the prospect of making a gain.

Have you noticed that whatever the detail under consideration, advocates of further European integration so often argue that Eurosceptics really want to leave the EU? This is to leverage the loss aversion of voters. They want to make voters fear the loss of current stability, knowing that this might prove a stronger emotion than the desire to gain greater national sovereignty. I am sure that the 1975 “yes” vote was swelled by the fact that we had already joined the EEC and the “no” voters wanted to come out.

A “yes” campaign for the treaty would emphasise that it had already been agreed, that the treaty consolidated existing understandings and that without it all would be chaos. These may not be good arguments, but they would be powerful influencers. It will be rough being on the other side.

I oppose the drive to integrate Europe and I dislike the new treaty. I want a referendum for this reason and because the Government fought an election promising one. To withdraw that promise now is an appalling breach of faith. But despite my desire to see the question put, I am constantly astonished at the faith that other Eurosceptics have about the outcome.

I think the treaty would have every chance in a referendum. If I were Gordon Brown, I’d risk it.

daniel.finkelstein@thetimes.co.uk

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