It may not have done much to help your teenage heartbreak at the time. But when your mother said that you’d have to kiss plenty of frogs to find your prince, she was right.

Oxford University scientists have concluded that kissing helps women meet their ideal man, because it allows them to assess their potential partners.

It gives them the chance to subconsciously weigh them up through taste or smell, and so glean information about their compatibility and general health.

Kissing also has a further role to play, they claimed, by keeping established couples together and reinforcing affection. More frequent kissing was linked to the quality of a relationship.

The researchers were trying to understand the purpose of the uniquely human practice. Lead researcher Rafael Wlodarski, from the university’s Department of Experimental Psychology, said: ‘Kissing in human sexual relationships is incredibly prevalent in various forms across just about every society and culture.

‘So here’s a human courtship behaviour which is incredibly widespread and common and, in extent, is quite unique. And we are still not exactly sure why it is so widespread or what purpose it serves.’

The research, published in the journal Human Nature, surveyed more than 900 adults to find out ‘what’s in a kiss?’. Just over half of the participants were in a serious relationship.

Those surveyed were asked about the importance of kissing in both short-term encounters and long-term partnerships.

Mr Wlodarski said: ‘There are three main theories about the role that kissing plays in sexual relationships: that it somehow helps assess the genetic quality of potential mates; that it is used to increase arousal (to initiate sex for example); and that it is useful in keeping relationships together.

'We wanted to see which of these theories held up under closer scrutiny.’

Women rated kissing as more important in relationships than men, the study showed.

Previous research has found that women are more selective when choosing a potential partner, perhaps because they have to invest more time and effort in child-raising than men. The team also found participants who viewed themselves as attractive, or who tended to have more casual encounters, rated kissing as being more important.

These individuals were also more likely to be more discerning when considering a possible mate.
All those who valued kissing more highly were pickier when considering partners, suggesting the practice is used to help assess their potential.

‘Our findings suggest that when we kiss information is passed on,’ said Mr Wlodarski. ‘It’s an excuse for two potential partners to get close enough together in a socially acceptable way and find out some extra information about potential desirability.

‘It could [be that] people are picking up chemical signals when they kiss, either from taste or smell, which subconsciously tell them if they are genetically compatible.’