THE Finns like a laugh. Famous for an annual wife-carrying competition, for regular success at the world air-guitar championship and record-breaking hurling of rubber boots and mobile phones, Finland can now claim another accolade: its citizens are reportedly the world's keenest pranksters. Celebrated for a full week at the beginning of April in the capital, Helsinki, and for weeks at a time in rural areas, the traditional “spring joke” in Finland has been raised to a national art form.

This long involved young men trying to catch the eye of women, typically by donning fancy dress (in the cold war a favourite was the garb of Soviet border guards) or through good-natured abduction—often in combination. More recently motorists have learned to watch for fake road-safety signs, which frequently cause springtime gridlock and collisions. Diplomats are increasingly wary of water-bomb attacks at functions—one thin-lipped European ambassador lodged a protest after being drenched in 2005. Even political leaders indulge. In 2003 the government apologised after stating that Finland wanted Sweden expelled from the European Union during a row about pickled herring.

But Finland's enthusiasm is not unique. Dr Is Poli-Savon, an anthropologist at the Paris-based Fairpooll Foundation, says that in many countries fooling is seen as a celebration of the end of winter. “In modern societies it serves as a rare chance for semi-subversive behaviour within safely defined parameters”, he says. Polls conducted by his team of researchers suggest that, despite suspicions to the contrary, many different cultures do share a common sense of humour.

A surprising number of German adults take part in April Fooling, along with many French (see chart) who mark “poisson d'avril” by sticking paper fish on each others' backs. Most Iranian jokers choose April 3rd, the 13th day of the Persian calendar, for mild joking. But not absolutely everyone sees the funny side. Adults in Equatorial Guinea, an oil-rich speck of a country in west Africa, are reportedly the least inclined to find anything to chuckle about. Fooling by anyone over the age of 13 years recently became a criminal offence, with exceptions only for the president and his extended family.