BEHAVIOURAL economics has long seemed to hold great promise. New insight into how people take decisions has the potential to improve the dismal science's ability to understand and model aggregate behaviour. It might also help policymakers "nudge" individuals away from dumb but common choices. As this week's Free exchange column explains, experiments with behavioural nudges are beginning to bear fruit:

The Nudge Unit has been running dozens of experiments and the early results have been promising. In one trial, a letter sent to non-payers of vehicle taxes was changed to use plainer English, along the line of “pay your tax or lose your car”. In some cases the letter was further personalised by including a photo of the car in question. The rewritten letter alone doubled the number of people paying the tax; the rewrite with the photo tripled it. Changes to language have had marked effects elsewhere, too. A study into the teaching of technical drawing in French schools found that if the subject was called “geometry” boys did better, but if it was called “drawing” girls did equally well or better. Teachers are now being trained to use the appropriate term.

Not every policy works effectively in every context:

Differences in culture can have a big impact, too. “Nudge” described an example in America, where telling high users of energy how their consumption compared with that of their neighbours prompted them to use less. This approach is now being tested in Britain. But hopes are low that it will work in France. “The French have a tendency not to comply as easily with perceived social norms the way Anglo-Saxons would,” says Olivier Oullier, a behavioural and brain scientist who advises the French government. “Telling someone in France that their neighbour is using less electricity or saving more water is not sufficient.”

Early hopes for a policy revolution may have proven overly ambitious. But as results come in, it seems likely that governments will learn how to craft rules and language in plainer and more useful ways—no small victory.