London, Oct 16 (IANS): Why the kissing? Nobody is quite sure what purpose it serves. But a research suggests it helps in assessing potential partners, and if in a relationship it may help in getting a partner to stick around.

"Kissing in human sexual relationships is incredibly prevalent in various forms across just about every society and culture," said Rafael Wlodarski, the D.Phil. student who carried out the research in the Department of Experimental Psychology at Oxford University.

"Kissing is seen in our closest primate relatives, the chimps and bonobos, though it is much less intense and less commonly used," said Wlodarski.

"So here's a human courtship behaviour, which is incredibly widespread and is quite unique. We are still not exactly sure why it is so widespread or what purpose it serves."

Rafael Wlodarski explains: "There are three main theories about the role of kissing in sexual relationships: it somehow helps assess the genetic quality of potential mates, or it is used to increase arousal (to initiate sex for example), or it is useful in keeping relationships together."

"We wanted to see which of these theories held up under closer scrutiny," said Wlodarski.