It seems as though the Cher hit It's In His Kiss was right all along.
Monroe: A perfect pout?
Scientists have found that the size of somebody's lips plays a key role in determining whether they are sexually attractive to other people.
Basically, the bigger the better - but, in a warning to those who are thinking about opting for surgical enhancement, it is possible for somebody to have lips that are too big.
And while men love a full pout on a women, the Mick Jaggers of this world are not necessarily on to a guaranteed winner with the opposite sex.
Professor Michael Cunningham, a psychologist from the University of Louisville, explained his findings to the BBC Radio Four programme The Kiss.
"Generally speaking, big is better than small," he said. "But it is possible to go a little too far and then be unattractive."
Pitt: Sensual and rugged?
Professor Cunningham said that women are looking for an elusive combination that suggests both sensuality and ruggedness.
However, it is also important that a man's lips should convey the impression that he is virile, and any sign of femininity is a big no-no.
"At the same time, there should be some hint of generosity and warmth," said Professor Cunningham.
"So medium-sized lips are probably better on men, than either too small or too large."
Robinson: Thin and mean?
The research suggests that men, on the other hand, are looking for a sizzling combination of fullness, redness and warmth.
And women who purse their lips send out a signal, subconsciously or not, that they are not really interested in a sexual advance.
According to Professor Cunningham: "If a woman is holding her lips very tightly clenched, that is not a good sign."
Professor Cunningham's team drew their conclusions from a series of experiments which involved making minute adjustments to parts of the face to find out how the changes altered sexual attraction.
They found that while good lips can make an attractive face even more attractive, they cannot salvage a face that is unattractive in other respects.
"The lips can convey real warmth and receptivity," said Professor Cunningham.
"They are so expressive, and when someone is genuinely pleased to see you, they flush and become fuller and darker.
"They show that sensuality and warmth that we all look out for in a partner."
Roy Levin, a psychologist from Sheffield University, UK, said the act of kissing was loaded with sensory stimulation.
Jagger: Too much?
"In the lips are touch and pressure receptors which fire off messages to the brain," he said.
"So you know straight away that this is a friend's kiss or a lover's kiss."
In general, the researchers found that a small nose, big eyes and voluptuous lips are sexually attractive both in men and women.
The Kiss is broadcast on BBC Radio Four on Tuesday 11 March at 1100 GMT.