Body signals if kisser is a keeper

While some die-hard romantics may insist they see stars when they kiss, it's really not magic at all, but chemistry and neuroscience.

And no matter how painstakingly you set the scene, in the end chemistry trumps mood music. From a scientific perspective, a kiss is a natural litmus test to help us identify a good partner.

Just what is it that makes kissing such a powerful and significant part of the human experience?

A kiss influences important chemicals in our brains and bodies responsible for promoting social bonding. According to the work of Rutgers University anthropologist Helen Fisher, kissing evolved to facilitate three essential needs: sex drive, romantic love and attachment. Each is involved in promoting reproduction, and kissing bolsters all three. In that view, locking lips helps us find partners, commit to one person and keep couples together long enough to have a child.

Humans use a number of signals — including taste, smell and possibly silent chemical messengers called pheromones — to help us figure out whether someone is a suitable partner and a good person to reproduce with. A kiss means getting close enough to suss out important clues about chemistry and genetics. At this range, our noses can detect valuable information about another person's health and perhaps even DNA.

Biologist Claus Wedekind has found, for instance, that women are most attracted to the scents of men with a different set of genetic coding for immunity than their own. This is probably because when there is greater genetic diversity between parents in this area, their children will have more versatile immune systems. The assessment occurs at a subconscious level, yet a bad initial kiss may be a result of a genetically star-crossed pair.

During a passionate kiss, our blood vessels dilate and our brains receive more oxygen than normal. Our breathing can become irregular and deepen. Our cheeks flush, our pulse quickens and our pupils dilate (which may be one reason that so many of us close our eyes). A long, open-mouthed exchange allows our tongues, covered with little bumps called papillae that feature 9,000 to 10,000 taste buds, to gather information about health and fertility.

When we kiss, all five of our senses are transmitting messages to our brain.

Billions of nerve connections are firing away and distributing signals around our bodies. Eventually, these signals reach the somatosenory cortex, the region of the brain that processes feelings of touch, temperature, pain and more.

Our brains respond by producing chemicals that help us decide our next move. A good kiss can work like a drug, influencing the hormones and neurotransmitters coursing through our bodies. It can send two people on a natural high by stimulating pleasure centers in the brain. The feeling has much to do with a neurotransmitter called dopamine, which is responsible for craving and desire and associated with “falling in love.” When it's really pumping, dopamine spurs us to take things further.

Kissing also promotes the “love hormone,” oxytocin, which works to maintain a special connection between two people; kissing can keep love alive when a relationship has survived decades, long after novelty has waned.

In other words, kissing influences the uptake of hormones and neurotransmitters beyond our conscious control, and these signals play a huge part in how we feel about each other.

A bad kiss, alternatively, can lead to chemical chaos. An uncomfortable environment or a poor match can stimulate the “stress hormone” cortisol, discouraging both partners from continuing.

Evolutionary psychologist Gordon Gallup of the University at Albany reports that 59 percent of men and 66 percent of women say they have ended a budding relationship because of a kiss that did not go well.

Whether it's magic or a disaster, that first kiss is likely to be unforgettable. Psychologist John Bohannon of Butler University and his research team surveyed 500 people to compare their recollections of a variety of significant life experiences — such as a first kiss and the loss of virginity — to find out what made the most dramatic impression. A first kiss trumped everything: It was the most vivid memory in the minds of those being surveyed.

Bohannon reported that most people could recall up to 90 percent of the details of the moment — where they were, who made the first move — no matter how long ago the exchange took place.

If that first kiss is a bust, remember that you can't control everything about the situation and that your body may be saying something very important: Look elsewhere. If the chemistry is wrong, there's not much you can do.

But take heart. Valentine's Day is less than two months away.