London: Humour in most men develops from aggression -- an it all starts at puberty, says a new study.

Researchers at Newcastle University have based their findings on an analysis of the reactions of men and women on seeing a trick cyclist, the 'Journal of Psychology Research and Behaviour Management' reported.

The results revealed big differences between male and female response -- nine out of 10 women would make warm, kind and encouraging remarks, while young children were interested and curious.

But as boys grew older, their reactions became increasingly unpleasant. Curiosity typically turned into physical and verbal aggression, and they would throw stones or attempt to obstruct the rider by shouting, "Fall off!"

Grown men suppressed the urge to injure the rider, but became snide and aggressive, and would often make jokes about the single wheel.

In fact, the researchers led by Prof Sam Shuster, studied data from more than 30 unicyclists aged between 15 and 69, from the UK and across the world, with up to 40 years' experience.

They discovered an astonishing consistency of responses from boys and men, regardless of social class, geography or era, which suggests a common biological mechanism. Changes in male hormones, which are associated with aggression, around the time of puberty, account for this.

"The consistent response to seeing a unicyclist is related to sexual development, suggesting that humour develops from aggression in males," 'The Independent' quoted Shuster as saying.

They have pointed out other links between aggression and humour: "Laughter associated with tickle, considered by some to be the origin of humour, is neurologically related to pain and moves easily into agony.

"A relationship between humour and aggression may also help explain the enjoyment of practical jokes, 'gallows humour' and the humour of verbal combat, whether over them dinner table or on the football terrace, where its enjoyment can relate to the discomfort it causes."

The study was borne out of personal experience.

Prof Shuster has described in the 'British Medical Journal' how he was tempted by the allure of a gleaming chrome unicycle: "My wife said buy it, which I did. After months of practice at home, I graduated to back streets, a small paved park, and finally town roads. I couldn't avoid being noticed;
I couldn't avoid observing the form that notice took."