"You don't have to be rich to be my girl. You don't have to be cool to rule my world. Ain't no particular sign I'm more compatible with. I just want your extra time and your ...Kiss."
DURHAM -- Hand it to Prince for capturing the allure of a kiss in those lyrics.
It's something almost everyone intuitively understands: A kiss is more than a kiss, and in fact, a good lip lock can seal a relationship.
The mystery of what makes a smooch smolder and why we do it prompted Sheril Kirshenbaum, a former research associate at the Duke University Nicholas School of the Environment, to study the passionate pastime and write "The Science of Kissing" (Grand Central Publishing).
"I didn't realize until I did this book how important the kiss is," said Kirshenbaum, now a University of Texas at Austin marine biology researcher. Kirshenbaum was at the Regulator Bookstore in Durham last month.
It takes chemistry
It might not be test tubes and Bunsen burners, but there's more real chemistry going on during a kiss than you probably want to contemplate during an embrace.
That fluttery feeling you get when you're kissing a new partner - the racing heart and spiking blood pressure - comes from dopamine. It revs your engine, but you can thank the love hormone, oxytocin, for bringing you back for more years after the novelty has worn away, Kirshenbaum said.
Science also suggests kisses can be our detectives. With each swirl of the tongue, our partner's saliva gives us hormonal clues about whether he or she would be a good companion for parenthood.
If you pucker up and the kiss is lifeless, your body could be telling you something. So, kiss your partner early and often, Kirshenbaum said, to see if you feel a sizzle.
Consider it the body's first line of defense against dating - or marrying - the wrong person, said University of Albany evolutionary psychologist Gordon Gallup Jr. It also gets us off the hook for trying to improve our kissing techniques.
"There's evidence to suggest that modifying your kissing ability might not be in your biological best interest," Gallup said. "If you push for a relationship after a lackluster kiss, that relationship could end poorly."
And don't discount the role your nose can play in bringing you in for a kiss. Scientists have evidence that while men might not be pigs, they certainly smell like them - and women, in fact, may like it.
It turns out that men have the same hormone - androstenone - in their sweat that male pigs have in their saliva.
Though smelling the hormone makes sows immediately receptive to mating, it doesn't exactly work like a magic elixir for women. However, in some experiments, women have shown a preference for chairs sprayed with the hormone, and men have conspicuously avoided the same seats.
"There are a lot of reasons to think that, as humans, we're picking up on something at an unconscious level," Kirshenbaum said. "Any woman who's ever lived in a college dorm with other women and ended up on the same menstrual cycle knows it's possible."
Can't we just kiss
and make up?
It turns out we can. Despite women's protests that a peck or two at the end of an argument isn't enough to get a man out of the dog house, scientific research disagrees. According to Gallup, studies show that kissing, and the oxytocin it pumps into the body, actually makes women more likely to dole out a reprieve.
It also shows that a kiss means something different to men and women.
"Research supports what we know about how men view kissing. They kiss as a means to an end," Gallup said. "Either they want to gain sexual favors or they want forgiveness for misbehavior."
It's also a tool men can use to their advantage, said Helen Fisher, a Rutgers University anthropologist who has studied kissing.
Saliva is swimming with testosterone, Fisher said, giving men the chance to slip the women they kiss a little extra hormone to get them in the mood. This added benefit of kissing could also explain why men are far more interested in sloppy, wet kisses than women are, Kirshenbaum said.
For women, though, kissing is less about sex and more about whether the relationship is solid or whether it's on the way down.
"We see a lot among committed couples that women view the amount of kissing as a barometer of the relationship's status," Gallup said. "In their minds, the more kissing there is, the more passionate it is, the more viable the relationship is."
And once you find the right person, there's only one way to keep the relationship simmering Kirshenbaum said. Just keep kissing.