Genetics may underlie humour

Men make more gags than women and their jokes tend to be more aggressive, Professor Sam Shuster, of Norfolk and Norwich University Hospital, says.

The unicycling doctor observed how the genders reacted to his "amusing" hobby.

Women tended to make encouraging, praising comments, while men jeered. The most aggressive were young men, he told the British Medical Journal.

Previous findings have suggested women and men differ in how they use and appreciate humour.

Women tend to tell fewer jokes than men and male comedians outnumber female ones.

Aggressively funny

Research suggests men are more likely to use humour aggressively by making others the butt of the joke.

And aggression - generally considered to be a more masculine trait - has been linked by some to testosterone exposure in the womb.

Professor Shuster believes humour develops from aggression caused by male hormones.

He documented the reaction of over 400 individuals to his unicycling antics through the streets of Newcastle upon Tyne.

The difference between the men and women was absolutely remarkable and consistent

Professor Shuster

Almost half of people responded verbally - more being men. Very few of the women made comic or snide remarks, while 75% of the men attempted comedy - mostly shouting out "Lost your wheel?", for example.

Mocking and sneering

Often the men's comments were mocking and intended as a put-down. Young men in cars were particularly aggressive - they lowered their windows and shouted abusively.

This type of behaviour decreased among older men however, who tended to offer more admiring comments, much like the women.

"The idea that unicycling is intrinsically funny does not explain the findings," said Professor Shuster.

The simplest explanation, he says, is the effect of male hormones such as testosterone.

"The difference between the men and women was absolutely remarkable and consistent," said Professor Shuster.

"At 11-13 years, the boys began to get really aggressive. Into puberty, the aggression became more marked, then it changed into a form of joke. The men were snide."

The initial aggressive intent seems to become channelled into a more subtle and sophisticated joke, so the aggression is hidden by wit, explained Professor Shuster.

Dr Nick Neave is a psychologist at the University of Northumbria who has been studying the physical, behavioural, and psychological effects of testosterone.

He suggested men might respond aggressively because they see the other unicycling man as a threat, attracting female attention away from themselves.

"This would be particularly challenging for young males entering the breeding market and thus it does not surprise me that their responses were the more threatening."