Children with older brothers and sisters find it easier to make people laugh, a survey has suggested.
Dawn French - proof that younger siblings are funny
Just over half of younger siblings questioned said it was easy to be humorous, compared with just a third of those who were first-born.
And just 11% of only children had the skill, according to the study of 1,000 people by psychologist Richard Wiseman.
Experts said younger children were more likely to feel the need to compete for parental attention.
And being funny continues into adulthood.
Famous younger siblings who went on to become comedians include Dawn French, Ricky Gervais, Rowan Atkinson and Kathy Burke.
Professor Wiseman, who compiled the Ocean Village Laughter Lines report, said his findings tied in with other research about the effect of family position on personality.
"The youngest has to compete for parental attention, so they have to be a bit more unconventional.
"They are risk-takers, and also more humorous.
"On the other hand, older children tend to take on much more serious roles. And only children don't feel the need to compete for attention."
He said University of California research had suggested that, because younger children had not had the chance to develop the same skills and abilities as their older siblings, they had to find novel ways of gaining attention.
This leads them to be more creative, unconventional, adventurous and rebellious.
The California team found that, while the majority of US presidents were first-borns - including Jimmy Carter, Bill Clinton and George W Bush, revolutionaries, including Marx and Castro were younger siblings.
The report also found gender differences in attitudes to humour.
Seventy per cent of women find it difficult to remember the punch line to jokes, compared with just 50% of men.
And 25% of men said they laughed most with their best friends compared with just 16% of women.
Men reported being successful when trying to make women laugh 71% of the time, compared with a lowly 39% success rate for women trying to make men laugh.
Professor Wiseman added: "The study reveals that laughter is hugely important to Britons with 82% stating they find it easy to make others laugh.
"The study reveals humour is not inherited but is moulded by our individual experiences."
Dr Sandra Wheatley, a social psychologist based in Leicestershire, said: "It is true that younger siblings tend to be that little bit more mischievous and more extroverted.
"They have to compete in what is a competitive market-place.
"They will therefore use a non-threatening, non-confrontational way of getting adults' attention."