On Valentine's Day, Sarah Woodley is offering insights into why people lock lips.

As it turns out, kissing is more than just mouth-to-mouth romantic revelry. Forgive us, Louie Armstrong, but a kiss is not just a kiss.

Kisses tell.

Dr. Woodley, an assistant professor in Duquesne University's Bayer School of Natural and Environmental Sciences, will participate today in a nationwide panel discussion in Chicago on The Science of Kissing, sponsored by the American Association for the Advancement of Science.

Based on her review of scientific literature, she said, kissing, especially for women, is a means to assess a potential mate. If kissing is forensics, ladies are FBI agents who use a robust smooch to evaluate their suspect.

During a kiss, odors, pheromones -- chemical substances that when secreted are believed to affect behavior in otherspgn -- and chemical interaction might help women and men evaluate genetic compatibility. In long-term relationships, the kiss is used to gauge continued interest and commitment, she said.

"Visual cues are the first stage of assessment," Dr. Woodley said. "Then when you are close enough, odors are the second stage of assessment."

OK, this is PG-13, but odors are gleaned from pheromones in the face, the smell of breath and the chemistry of saliva.

Dr. Woodley is an expert in pheromones that salamanders and other creatures use as mating signals. Her topic today is "Pheromones and Human Mate Choice."

Whether pheromones affect humans has long been studied and debated, without clear results.

Even if they don't work biologically, Dr. Woodley said commercial products containing pheromones might have a placebo effect that brings romantic good fortune.

To perpetuate his genes, a male salamander rubs the gland under his chin against the female's nose to signal his desires. It's the salamander version of a pickup line, wine and roses.

For humans, pheromones might do no more than pave the way for further evaluation.

Suspected human pheromones include androstenone and androstadienone, which may affect mood and the flight or fight response. The question is whether humans excrete enough of these compounds to elicit a response.

Humans use artificial pheromones -- colognes and perfumes -- that mask real ones. But studies suggest that perfumes can enhance natural body odors. People also might use the redolence to judge whether the person splashed on the expensive stuff.

"We have replaced natural pheromones with unnatural odors -- perfumes -- as a way of advertising earning potential," Dr. Woodley said.

Other romantic cues include the smell of the scalp and hair, and women's preference for men with lower voices. "When we select mates, we rely on a whole constellation of sensory cues," Dr. Woodley said.

The human armpit is full of glands, and sweaty T-shirt studies have shown that women react favorably to male armpit odors. What sounds disgusting proves that Americans have developed a cultural aversion to such natural odors and signals.

But armpit odors might provide females with a means to gauge testosterone levels related to muscle development, strength and robustness of the immune system -- all things women generally seek in a male partner, Dr. Woodley said.

Saliva also offers important odors for evaluation. Several diseases can be detected in the breath. Kissing also gives a person an opportunity to evaluate the quality of teeth -- another health indicator.

When romantic partners get close, senses sharpen. "It is my goal to understand the general principles of chemical communication in invertebrates and humans as well," Dr. Woodley said.

Perhaps, she joked, she should open a scratch-and-sniff dating service.

"People love the idea of odors controlling us," Dr. Woodley said. "I would argue that odors are important in the quality of life."

So pucker up, people. It's time to be tested.