American scientists 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.

Researchers conducting this vital work have found that young men are three times more likely to take this plunge than their girlfriends.

According to researchers, there may be a more cynical explanation – that the men are simply trying to smooth-talk their partners into bed.

They explained: “Any strategy serving as the means to a sexual end would be beneficial to men, including declarations of love.”

American scientists 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

They came to their conclusion after interviewing 171 heterosexual students under 25.

A sizeable majority (87 per cent) of the group 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 realize they had fallen in love, compared with a few months for women.

It is probably no coincidence that this coincides with the average timescale when each partner wanted to have sex – within weeks for men and months for women.

Some 64% of men admitted they had said “I love you” first, compared with just 18% of women.

The research from Pennsylvania State University and published in the Journal of Social Psychology, concluded: “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.”

Meanwhile, a separate study has found women are wary of men with a squinty gaze because they look promiscuous.

Hundreds of participants were shown three images of the same male face, but with eyes altered by computer. Women said the man with narrowed eyelids looked as if he would challenge authority, sleep around and steal another man’s girlfriend.

The man with an open gaze was considered more caring and emotionally supportive – and therefore better husband material.

Researchers from the University of Michigan said the simplest explanation was that “a lowered eyelid gaze is a display of sexual interest”.