Did you hear about the blond who could dumb men down?

Paris researchers have found that otherwise intelligent men performed below par after being shown pictures of fair-haired women - apparently believing they were dealing with someone less intelligent than they, a recent study says.

The researchers, from the Université Paris X Nanterre, found that the women's blond tresses didn't just put the men off their game: The men, by subconsciously reacting to the stereotype of the "blond bimbo," thought they were acting in their own version of Dumb and Dumber.

The study examined men's ability to complete general knowledge tests after exposure to women with different hair colours, according to news reports yesterday.

Throughout both trials, those participants exposed to blonds recorded the lowest scores.

"This proves that people confronted with stereotypes generally behave in line with them," said Thierry Meyer, a joint author of the study and professor of social psychology at the university.

"In this case, blonds have the potential to make people act in a dumber way because they mimic the unconscious stereotype of the dumb blond," he said.

The study, published in the Journal of Experimental Psychology, is not the first to suggest that human behaviour is strongly influenced by stereotypes, according to the Daily Telegraph in London.

Scientists have found people walk and talk more slowly in front of the elderly while other studies revealed female leaders were evaluated more harshly than male ones.

Although the origin of the "dumb blond" stereotype is unclear, some suggest the first holder of the title was an 18th-century Parisian prostitute called Rosalie Duthé, famous for her long silences.

Duthé became the subject of a one-act play that was said to have kept Paris laughing for weeks.

Speaking of Paris and dumb blonds ... the contemporary image of the bubble-headed bleach blond would be the "heirhead" herself, Paris Hilton, of the hotel family. Her contemporaries would include singers Britney Spears and Jessica Simpson.

The modern image of the dizzy blond came to prominence in the 1925 Anita Loos novel Gentlemen Prefer Blondes. The Howard Hawks film in 1953 starred Marilyn Monroe, herself a blond, though not a natural one. In the 1960s and 1970s, Goldie Hawn and Suzanne Somers further popularized the "dumb blond."

How blonds developed a reputation for dizziness is unclear, though the roles Monroe played might have helped the process along. A typical Monroe line, from Some Like It Hot: "Real

diamonds! They must be worth their weight in gold!"

Certainly "blond jokes" are a popular if not politically incorrect entertainment.

An example (as if another were needed, but in case this hasn't made the rounds yet):

Q: What do you call a blond with two brain cells?

A: Pregnant.

Whether natural or from a bottle, blond hair has gone hand in hand with beauty or sex appeal since long before Ringo Starr and Shelley Long starred in Caveman.

Last year, researchers found that cavemen preferred blond mates because fair hair was an indication of higher levels of estrogen and fertility.

"With very intense sexual selection, you get chosen for bright colours. We see this in birds and mammals," Peter Frost, a Université Laval research associate in anthropology, told the Toronto Star. Frost's work was published in Evolution and Human Behaviour. "In a very competitive market, you have to stand out visually."

The dumb-blond stereotype is being pushed aside in favour of the power blond - Madonna, Hillary Clinton, Kim Campbell, Pauline Marois and Diana, the late princess of Wales - and the intelligent blond: J.K. Rowling, author of the Harry Potter series, Martha Stewart, Lesley Stahl, Diane Sawyer and Pamela Wallin.

Real-life blonds were skeptical about the findings. Laura Bailey, a Marks & Spencer model, told the Times in London: "I've always been taken very seriously. I have always been blond and I have never had an issue with the way I am. If I'm being insulted, then I'm blissfully unaware."

And blond actor Michelle Collins, who starred in the BBC's EastEnders series, suspected the results were more to do with men's approach to sex than intelligence. "I don't think it's to do with hair at all; it's all about the breasts," she said.

"But if someone walks round with extensions down to their bottom, even I would treat them differently," she told the Times.