Washington: In a surprising challenge to age-old stereotypes, researchers have discovered that it is the man, not the woman, who is most likely to be the first to say 'I love you' in a blossoming romance.

American scientists conducting the research have found that young men are three times more likely to take this plunge than their girlfriends.

Researchers at the Pennsylvania State University interviewed 171 heterosexual students under 25. 87 per cent said they believed women fell in love first, while three-quarters said they expected women to say 'I love you' first.

But when asked about their own experiences, men said it took them a few weeks to realise they had fallen in love, compared with a few months for women.

However, researchers say that men are simply trying to get their partners into bed.

"Any strategy serving as the means to a sexual end would be beneficial to men, including declarations of love," the Daily Mail quoted the researchers as saying.

Some 64 per cent of men admitted they had said 'I love you' first, compared with just 18 per cent of women.

"This shows that women tend to be more cautious about love and the expression thereof than is commonly believed. It can be argued that men's falling in love and exclaiming this love first may be explained as a by-product of men equating love with sexual desire," said researchers.

The study was published in the Journal Of Social Psychology.