It took a long time. Longer than it should have. But in the end, the penny dropped.

Back in the 1980s, Tony Blair, a junior Shadow minister, was sitting quietly with his constituency agent, John Burton, when he suddenly exclaimed: “You know, John, I understand it all. Finally, I've got it.” When Burton asked him what he was talking about, Blair triumphantly replied: “Microeconomics!”

Twenty years later the remark seems charmingly naive. Could a Labour spokesman with an economic portfolio really have been so pleased to understand the basic ideas of supply and demand, pricing and competition? But at the time it was a considerable intellectual achievement for a politician of the Left, and it was to prove an important political moment too.

I wonder whether in a couple of decades' time, our own fumbling first acquaintance with new thinking will appear similarly amusing. For an intellectual revolution is under way that will change the way we think about public policy just as the free market economists did in the 1980s. I wonder whether one day soon a future party leader will turn round to his agent and say: “Finally, I've got it! Human behaviour.”

Those who doubt that there is something going on in the world of ideas should get themselves a publisher's catalogue. One month there is a book called Nudge, the next a book called Sway. A volume called Predictably Irrational follows another called Irrationality. Since the success of Malcolm Gladwell's Tipping Point, books on tipping points have reached a tipping point.

Behind this publishing explosion, with its PR hoopla, is real and solid intellectual progress. It comes from two streams of thought, developing alongside each other. The first is the idea of evolutionary psychology.

The breakthrough came with E.O. Wilson's controversial work Sociobiology, first published in 1975. Since then a number of academics, including familiar names such as Richard Dawkins and Steven Pinker, have illuminated aspects of human behaviour by explaining how they arise from our Darwinian struggle. For example, we reciprocate favours because we are the genetic descendants of those who survived to breed because they reciprocated favours.

Why was this work controversial? Because it argued that behaviour is partly inherited, offending against those who believe that we are born completely free of such influence. As Pinker explains in his unmissable book The Blank Slate, the critics have really lost the battle, even if they haven't given up.

The second stream of thought is behavioural economics. For twenty years now, some economists have been looking at the psychology of economic decision-making. Instead of seeing humans as rational calculating machines, behavioural economists have been conducting experiments to assess how real choices are made. On paper, two alternatives may look economically identical. But the way that they are framed and the context will, in the real world, determine the choice. Human beings are, for instance, highly loss-averse. They will take risks to avoid a loss, while behaving conservatively when a possible gain is in the offing.

This work has revolutionised economic thinking and helped to win Daniel Kahneman the Nobel Prize for Economics in 2002. This was the prize that Milton Friedman won in 1976, just before monetarism swept all before it.

All this does not overturn classical economics. It enriches our understanding of it. It suggests that there is such a thing as society and you can't understand the impact of policy on individuals unless you realise that. We are not just individuals. We abide by social norms, reciprocate favours, stick by our commitments, are desperate to remain consistent and are tribal.

And you can see already this work seeping into the political mainstream. There's been a flutter of interest in Nudge and in Robert Cialdini's seminal book Influence. George Osborne has written this week of social psychology, and his Tory frontbench colleague Greg Clark takes a close interest. On the Labour side James Purnell shows some familiarity and the former Blair aide Matthew Taylor is turning the Royal Society of Arts into one of the leading think-tanks in this area.

The most important step forward has come with David Cameron's correct insistence that social change is as likely, or more likely, to come through influencing behaviour as it is through regulation.

Yet the integration of the academic work on human behaviour into politics is still very much in its infancy. It is roughly now where economic understanding was in about 1978, before the Thatcher revolution. It is possible, indeed usual, to have entire policy debates in which the science of human behaviour doesn't figure at all.

For instance, in the past two weeks we have had discussion of obesity and of knife crime. Social norms have hardly figured. If everybody thinks that everybody else is getting fat, then more people will put on weight. The campaigns designed to reduce obesity may be spreading it. Similarly the very idea that every young person is carrying a knife increases knife crime. The obvious route of making such behaviour seem odd and isolated appears not to have occurred to any major politician.

Similarly, the work of social psychologists on the power of public commitments is entirely absent from the debate on marriage and on reducing delinquency; and our struggle to overcome our tribal instincts doesn't figure in the discussion of immigration.

It now seems hard to imagine political debate without rudimentary economic understanding. But we haven't always had it. It's quite a recent thing. The time will come when we feel the same about social psychology.

daniel.finkelstein@thetimes.co.uk

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