Feb. 14, 2011 -- Psychologists report that most people can remember up to 90 percent of the details of their first romantic kiss, a memory that is even more powerful than their first sexual encounter.
The "Shoop-Shoop Song, (It's in His Kiss)," sung by both Betty Everett and later Cher, says it all.
"Think about all those date-movies where that long-awaited first kiss brings sighs and heart flutters to the audience and seals the deal between the couples on the screen," said Sarasota, Fla., psychologist and licensed clinical social worker LeslieBeth Wish.
"The lips are very sensitive tissue, with many nerve endings that signal reactions such as hot and cold, sharp and soft," she said. "These same nerve endings also activate our feelings of closeness and attachment by arousing the brain's love chemicals such as oxytocin."
On Valentine's Day it is worth noting that the romantic kiss may be underrated in a fast culture that celebrates booty calls, pornography and online dating.
"Despite the casualness of sex these days, kisses still pack a serious punch," said Wish. "Good kissers know not to swallow up the mouth of the other, not to jam their tongue down the partner's throat or knock their teeth. Kisses are such powerful connectors that the moment of the first touch can overwhelm you with pleasure."
From Alfred Eisenstaedt's famous photo of the sailor kissing the nurse after World War II, to the lip-lock of gay cowboys Heath Ledger and Jake Gyllenhaal in the 2005 film "Brokeback Mountain", a relationship can truly be sealed with a kiss.
It can also break the deal.
"The worst kiss is the kind when it feels like a serpent has just entered your mouth and is swirling around inside of it," said Severin Witte, a 22-year-old college senior from Brenham, Texas.
An estimated 59 percent of men and 66 percent of women end a relationship because of a bad first kiss, according to Sheril Kirshenbaum, author of "The Science of Kissing: What Our Lips Are Telling Us."
"So much information is exchanged with a kiss," she said. "One kiss and everything can be completely off. It's the ultimate litmus test."
Research for her recent book revealed that, as a rule, "men prefer open-mouth kissing, and women complain about too much tongue," said Kirshenbaum.
The kiss may even serve an evolutionary purpose. Men's saliva contains a small amount of testosterone that can, over repeated exposure, arouse a woman's libido and eventually persuade her to mate.
In a a study at the State University of New York at Albany, men described kissing as a "means to an end...something else down the line," but women saw it as a route to a deeper relationship, according to Kirshenbaum.
Women are also more sensitive to scent and taste, using their senses to detect if the man is the "right match."
"Kissing is such a good example of a behavior that is both nature and nurture," she said. "We seem to have an instinctive drive to kiss and connect in some way."
Man's earliest kisses were with the nose, kind of like the Eskimo rub, according to Kirshenbaum, probably allowing humans to reconnect with relatives and find out clues about a person's health.
Kissing may have moved to the mouth as humans became sensitized to the color red, finding ripe fruits for food. That may have led to a woman's red lips, an indicator of a potentially fertile mate. Modern studies show that the color red makes the heart beat faster and may be the reason why women still use lipstick.
The first mention of a mouth kiss -- "smelling with the mouth" -- was in India's Sanskrit texts in 1500 B.C. Later, in the third century A.D., the Kama Sutra instructed readers to kiss "the forehead, the eyes, the cheeks, the throat, the bosom, the breasts, the lips and the interior of the mouth."
Kissing went on to become an act of greeting or reverence, not only sexuality. Greeks and Romans chronicled kisses between slaves and owners; Christians kissed the hands of priests and popes.
In the Middle Ages among the illiterate, legal documents were marked with an X and sealed with a kiss. But by the time the plague arrived in the 17th century, a kiss became deadly and men were more apt to tip a hat than risk touching lips.
Some of the most memorable kisses have come out of Hollywood.
Burt Lancaster's famous kiss in the surf with Deborah Kerr in the 1953 film "From Here to Eternity," still ranks as the most memorable of all screen kisses, as rated by entertainment writer Erik Lundegaard. Tobey Maguire and Kirsten Dunst ranked second in their upside-down kiss in the 2002 movie "Spider-Man," followed by George Peppard and Audrey Hepburn in the 1961 film "Breakfast at Tiffany's," and Patrick Swayze and Demi Moore in the 1990 move "Ghost."
Kissing can even be good for your health.
According to the American Academy of Cosmetic Dentistry, when people kiss, salivary glands under the tongue and in the cheeks are stimulated to produce more saliva. The water, proteins, electrolytes and mineral salts in saliva keep the mouth healthy.
Some cold medications and painkillers may reduce the flow of saliva and kissing can boost production, they say.
What makes a good kisser?
"I like when he takes charge...but not too aggressive," said Kendra Handy, 21, of Snellville, Ga. "I like to feel engaged -- kissing is about more than just lip."
Ashley Boyce, 21, of Bandera, Texas, said a good kiss has "just the right amount of tongue-to-lips-to-teeth ratio."
And it always has to be an appropriate setting, not a busy street corner or school hallway," she said. "In the 'Wedding Singer' they call it 'church tongue'!"
And women don't have to be gay to appreciate a good kiss with another woman.
Annette Bening told ABC News in a recent interview that her co-star in the film "The Kids Are All Right," Julianne Moore, was "at the top" of her list of great kissers.
"We've actually talked about this," Bening said, referring to Moore. "Because both of us have kissed a lot of guys, OK? That's the bottom line. So, we both agree we'd much rather kiss each other than many of the men we've had to kiss."
Kissing in Public Can Be 'Gross'
What is so breathtaking in private can be repulsive in public.
"The worst public kiss I have ever seen was in Penn Station," said Kelly Freund, a 21-year-old college senior from Massapequa, N.Y. "This woman wearing bright pink lipstick and she was attacking her man. They were in their fifties or sixties, and when she left he turned around and had smeared pink lipstick stains all over and around his mouth."
"I saw a couple kissing…and the guy's mouth was entirely covering the girl's mouth…I couldn't tell if he was kissing her or suffocating her," said Jon Tan, 21, from Boston.
Cierra Jones, a 22-year-old college student who works as a waitress in Huntsville, Ala., said, "I hate when people kiss at my tables full-on."
"I've seen a guy with a girl laying on a car in front of a mall, completely making out. It was so gross," said Kaitlyn Baisch, a freshman at Arizona State University.
Baisch prefers something more sublime. Her favorite movie kiss is the spaghetti scene in Disney's classic cartoon film, "Lady and the Tramp."
"It may have looked like an accident with the spaghetti," she said. "But Tramp knew exactly what he was doing."
Online phenomena like Second Life, social networking and dating websites may be doing relationships a disservice, according to author Kirshenbaum.
She fears potential lovers are "acting without the [sensory] signals that have evolved over time. When you can't sense and taste but only see a good match with a photo visual, you are flying blind, could be missing someone who is great."
Geoffrey Michaelson, a Virginia psychologist who is on the faculty of the Human Sexuality Institute in Washington, D.C., said the kiss is essential to relationships -- "the touch of the lips is rare, like a fingerprint."
"In romance, the kiss takes us toward emotional intimacy," he said. "We face our beloved, look into their eyes, or close the eyes as we reach deeper into the soul of the experience, crossing the line between our separate selves and our deepest longings to be part of something more."
ABC On-Campus reporters Candace Smith, Chelsea Smith and Ashley Jennings contributed to this report.