A German academic sees humour as an act of aggression, and says that people who make others laugh think that they are higher up the social ladder than their audiences.

"Displaying humour means taking control of the situation from those higher up the hierarchy and this is risky for people of lower status, which before the 1960s meant women rarely made other people laugh -- they couldn't afford to.

"Comedy and satire are based on aggressiveness and not being nice. Until the 1960s it was seen as unladylike to be funny. But even now women tend to prefer telling jokes at their own expense and men tend to prefer telling jokes at other people's expense," she added.

According to Helga, the differences between men's and women's ability to become comedians starts very young. She supports this by pointing out that boys as young as four can be seen telling more jokes, frolicking, and clowning about, whereas the girls tend to be the ones doing the laughing.

Men, on the other hand, often use humour to vent frustration, she says.

She said: "For example, doctors sometimes use humour to comfort patients but also to silence them if, for example, the patient displays too much knowledge of a medical condition. Nurses and midwives tend to tell jokes about patients but not when the doctor is present. And when someone initiates a joke they tend to be ignored if they are in the presence of someone of a higher status."

Helga even suggested that it was because of the fact that most humour is an act of aggression that women rarely became comediennes in public or private until the sexual revolution of the 1960s.

"A study in the late 1980s showed that men use sexual jokes as a way of verbally undressing a woman who rebuts his advances; his humour was aggressive in essence," she said.