THE true story of how your wife's stalker rang her to discuss killing you isn't supposed to provoke mirth. But when John Morreall, of the College of William and Mary in Virginia, related the events last week to a group of scholars in Tuebingen in Germany, they were in stitches as he divulged the details of how his wife tried to dissuade the confused young man by pleading that her mortgage was too large to pay without her husband's help.

So why did they laugh? Dr Morreall's thesis is that laughter, incapacitating as it can be, is a convincing signal that the danger has passed. The reaction of the psychologists, linguists, philosophers and professional clowns attending the Fifth International Summer School on Humour and Laughter illustrates his point. Dr Morreall survived to tell the tale and so had an easy time making it sound funny.

One description of how laughter is provoked is the incongruity theory developed by Victor Raskin of Purdue University and Salvatore Attardo of Youngstown State University, both in America. This theory says that all written jokes and many other humorous situations are based on an incongruity—something that is not quite right. In many jokes, the teller sets up the story with this incongruity present and the punch line then resolves it, in a way people do not expect. Alternatively, the very last words of the story may introduce the absurdity and leave the listeners with the task of reconciling it. For instance, many people find it funny that a conference on humour could take place in Germany.

Why do people laugh at all? What is the point of it? Laughter is very contagious and this suggests that it may have become a part of human behaviour because it promotes social bonding. When a group of people laughs, the message seems to be “relax, you are among friends”.

Indeed, humour is one way of dealing with the fact that humans are “excrement-producing poets and imperfect lovers”, says Appletree Rodden of the University of Tuebingen. He sees religion and humour as different, and perhaps competing, ways for people to accept death and the general unsatisfactoriness of the world. Perhaps that is why, as Dr Morreall calculates in a forthcoming article in the journal Humor, 95% of the writings that he sampled from important Christian scholars through the centuries disapproved of humour, linking it to insincerity and idleness.

Fear of idleness is why many managers discourage laughter during office hours, Dr Morreall notes. This is foolish, he claims. Laughter or its absence may be the best clue a manager has about the work environment and the mood of employees.

Indeed, another theory of why people laugh—the superiority theory—says that people laugh to assert that they are on a level equal to or higher than those around them. Research has shown that bosses tend to crack more jokes than do their employees. Women laugh much more in the presence of men, and men generally tell more jokes in the presence of women. Men have even been shown to laugh much more quietly around women, while laughing louder when in a group of men.

But laughter does not unite us all. There are those who have a pathological fear that others will laugh at them. Sufferers avoid situations where there will be laughter, which means most places where people meet. Willibald Ruch of Zurich University surveyed 1,000 Germans and asked them whether they thought they were the butts of jokes and found that almost 10% felt this way. These people also tended to classify taped laughter as jeering. Future research will focus on the hypothesis that there is something seriously wrong with their sense of humour.