The science of lust

Birds do it, bees do it, even educated fleas do it, but do they know why? Claire Keeton takes a look at the chemicals that encourage us to fall in love (or lust)

Why do the arrows in Cupid's bow make your pupils dilate and why does your heart race when you meet someone you're attracted to? Our bodies emit potent cues for sexual attraction so, even in the age of online dating, cybersex and Second Life, it's still desirable to meet a potential mate face to face.

This sexual magnetism involves hormones, genes, instincts (straight from the animal kingdom) and nonverbal signals. The brain and subconscious also influence what turns a man or woman on and makes them fall for the same "type" again and again.

"What really goes on when we fall in love or in lust" is explored by US scientist Jena Pincott in the book Do Gentlemen Really Prefer Blondes? Why He Fancies You and Why He Doesn't.

And just to make sure this is not all about American preferences, South African sexologists Professor Elna McIntosh and Dr Marlene Wasserman have shared their knowledge of sexual attraction with us.

• Mating cues

Pheromones, chemical signals that may make you happier and hornier, are high on the list of invisible cues.

"You would inhale them in the air as you would a perfume, or by kissing," says Pincott. "Pheromones are chemicals in sweat, saliva, semen, breast milk and other body fluids.

"There's increasing evidence that pheromones also influence our love lives in subtle ways - they're much more subtle than hormones," Pincott told Lifestyle.

"One type of pheromone is linked to a cluster of immune system genes. Studies show that a woman will prefer the body odour of a man who has immune system genes that are mostly different from her own (this is good for the survival of the species).

"When it comes to sexual attraction, both pheromones and hormones are important," Pincott says. "You wouldn't have much of a sex drive if you didn't have hormones - especially testosterone and estrogen - and hormones also help shape your features."

• Visual cues

Sexy curves, and the colour and length of hair (or penis) have the power to inflame sexual attraction or subdue it, explains Pincott.

Wasserman, also known as Dr Eve, says: "For men the first point of attraction is always going to be visual. Interestingly, research shows that for women smell is their primary attractant to a man."

For men of all ages, the perfectly proportional waist to hip ratio signals that a woman is "hot", healthy and fertile.

"Women are attracted to men visually too and they look for shoulder to hip ratio. This is a sign of strength and good health," says Wasserman.

And, yes, while it's true that American men are more attracted to long blonde hair, other US studies have found that women also rate hair as an important part of male attractiveness.

Pincott explains: "Hair is an honest record of the food you've eaten, the drugs you've taken, the seasons you've weathered, the stresses and sicknesses you've endured and the grooming you've given it."

And now for the sensitive question: does size really matter?

"Among men, penis size is a universal way of sizing up masculinity. In one large-scale survey, nearly half of the men said they'd like a larger penis. But, and this may come as a surprise to some, most women (9 in every 10) say they are satisfied with most men's penises," says Pincott.

Bigger breasts, however, do attract more attention - perhaps as a sign of "increased fertility".

• Is it all in the mind?

When it comes to the biology of love, the brain must rank supreme.

The amygdala region of the brain influences the libido and is "associated with emotions, urges and spur-of-the-moment decisions", writes Pincott, referring to several studies. This region controls the release of dopamine "a feel-good neuro-transmitter that is associated with passion and addiction and oxytocin, a hormone related to bonding".

She describes a chemical cocktail that makes people rapturous during the first rush of falling in love.

"Like any addictive drug, the effects of early love gradually wear off (usually within a year) and the chemical tsunami in your brain becomes a gently lapping pool, subject only to occasional storms," she writes.

• The love map

Shifting from hormonal to subconscious desire, psychologist John Money has developed the concept of a "love map". This is a network of subconscious preferences, shaped in childhood, which creates an imprint of each person's fantasy or ideal lover.

McIntosh, president of the Sub Saharan Africa Society of Sexual Health Therapists, says: "This explains who we are attracted to and why. It explains why someone catches your eye and why people tend to marry or date the same type of person over and over again. Love maps are made of both positive and negative elements."

And these feelings go beyond just physical attraction. As Wasserman says: "Sexual attraction is instantaneous when two people meet, even via the Internet. It is the X factor. No one can say why it happens, but when it happens one feels it."

• Nonverbal signals

Even though sexual attraction may feel mysterious, some of the cues and clues to bonding are well known. Up to 90% of communication can be nonverbal, says McIntosh, suggesting: "When dating and mating, it's important to make sure your body language is as sharp as your conversation skills."

Pincott reviews studies that show that gazing into someone's eyes, deep voices (men) and higher, dulcet voices (women) and a direct, sincere smile are a winning combination to signal attraction. Mimicking another person's expressions and body language also encourage intimacy.

She says: "Never underestimate the power of body language. In one fascinating study, women who made 35 signals an hour - like smiling, making eye contact, facing herself in a man's direction - were approached by an average of four men, whereas women who didn't signal were not approached at all.

"Guys approached plainer women who gave signals more often than they approached very pretty women who didn't."

• Last word

If you find your match on Valentine's Day, you may want to heed this tip from US psychologist and agony aunt Professor Duana Welch - don't stop dating others just yet or you'll lose status and possibly your new partner.

Welch, who writes the blog Love Science: Research-based relationship advice, suggests that status is marked by youth, beauty and being "somewhat hard to get".

"Being (not playing) hard to get by staying in the dating pool increases desirability and benefits a new relationship," she writes.

"Combined with early sexual restraint, it effectively screens out Mr Right Now, but not Mr Right."