"Fate of a couple is sealed with first kiss":

While a kiss may just be a kiss for a man, for a woman it’s an all-important means of gauging a prospective partner's compatability. She uses it, the study suggests, to assess a "rich and complex exchange" of romantic and chemical clues that pass between partners as their lips touch.

A "good kiss" will help convince her that the partner is worth perservering with but a man who is judged to be a bad kisser is unlikely to find himself invited in for coffee.

In the longer term the woman treats kissing as a means to induce bonding and to help her assess whether her partner has remained faithful and interested.

(Via Cosmic Log.)