Great topic. I just wanted to add my 2 cents. I've found when I kiss, I have very different reactions, due to the original intent of the kiss. When I kiss my child, for example, is much different than when kissing a woman for sexual gratification. In that case it's like my lips feel like there is a direct connection to my penis and I get aroused. Whereas, after I have kissed my kid, I just have told them I love them, as can be the case when kissing a woman, but the intent of the kiss was different. I know that hasn't got much really to do with why humans kiss in the first place but that's my view anyway.