A rival psychologist has published a book debunking the behavioural economics of Daniel Kahneman and the men behind Nudge, who, along with the authors of Freakonomics, were once the PM's pet thinkers. So how do you choose between them? In a TED talk in Monterey, California in February 2010, just before he came to power and had to make decisions, David Cameron was extremely keen to look like the future. "Politicians will only succeed if they actually try to treat people as they are, rather than as they would like them to be," was his fresh-faced rallying cry, as he attempted to channel the spirit of Bobby Kennedy in an open-necked shirt. "If you combine this very simple, very conservative thought – go with the grain of human nature! – with all the advances in behavioural economics, I think we can achieve a real increase in wellbeing, in happiness, in a stronger society without necessarily having to spend a whole lot more money.This "revolution in government" would be brought about in particular, Cameron suggested, by his devotion to the theories of a group of thinkers who had come to establish and dominate a new self-help/psychology/economics corner of the bookshop, the decision-makers' decision-makers. "We are working with these people," Cameron said proudly, and flashed up a slide featuring three of them: Cass Sunstein and Richard Thaler, authors of the bestsellingNudge, and Daniel Kahneman, Nobel prize winner and author of the soon-to-be bestsellingThinking, Fast and Slow.