Big is better: Brad Pitt

Forget hour-glass figures or bulging muscles. They may play their part in opposite-sex attraction but a 15-year study has identified a new measure of desire — lips.

Prof Michael Cunningham, from the University of Louisville, Kentucky, has found that couples are attracted by the size of each other’s lips.

“Larger lips are better-looking than smaller lips up to a certain point,” he said. “It is possible to go a little too far and then be unattractive. But generally speaking, big is better than small.”

Men and women have different tastes about the size of lips that they prefer in their partners, Prof Cunningham told Radio 4’s programme, The Kiss, to be broadcast next Tuesday.

“When women are looking at men, they are simultaneously looking for sensuality and ruggedness,” he said. “And that is, the man should look virile, which means that he shouldn’t look too sensual. He shouldn’t look too feminine in his lips.

“At the same time, there should be some hint of generosity and warmth. So medium-sized lips are probably better on men, than either too small or too large.”

The programme’s presenter, Gillian Rice, suggests that the singer Mick Jagger should “move over”, making way for men with “delectable lips” such as the actors Johnny Depp and Brad Pitt.

In general, a small nose, big eyes and voluptuous lips are sexually attractive in men and women, although it is possible to take any of these descriptions too far.

Men are looking for lips that have “fullness, rednessand warmth”. Pursed lips, a speciality of Anne Robinson on The Weakest Link, should act as a warning signal to a man who is looking for a girlfriend. “If a woman is holding her lips very tightly clenched, that is not a good sign that she is really interested in getting to know you better,” he said.

Since the mid-1980s, Cunningham has devoted much of his working life to the science of attractiveness.

Much of his work involves carrying out minute adjustments to the size of parts of the face to find out how changes to the fullness of the lips or the width of the nose alters people’s attraction towards another person.

“Lips can certainly enhance the attractiveness of an attractive face,” he said. “But they can’t always salvage a face that is unattractive.”

Lips rank high on the list of factors that make up somebody’s beauty, or ugliness, although the eyes, cheekbones, the nose and the smile are even more important.

The programme also points out that a person who licks their lips before kissing is putting up to three million bacteria on to the surface of their lips.

Saliva, it explains, contains “a veritable broth of bacteria”.

Prof Stephen Challacombe, an oral medicine consultant at Guy’s Hospital in London, said: “Saliva is one of the most useful body fluids. I suppose there would be those who say that it does not have the drama of blood or the emotion of tears, but it is actually hugely useful.”