But there are other biological and evolutionary triggers which are constantly drawing us to certain individuals, even if we don’t realise it is happening. Scientists in Geneva discovered that determining whether we are attracted to someone is one of the most complex tasks that the brain undertakes. Here are the scientific secrets of attraction:
Charles Darwin once wrote: "It is certainly not true that there is in the mind of man any universal standards of beauty with respect to the human body."
Probably the most important is facial symmetry. Having a face which is equal on both sides is a biological advert which tells prospective partners that good genes will be found in this body.
Lopsidedness is thought to reflect how development in the womb has been derailed by general poor health, bad DNA, alcohol or tobacco use.
Facial symmetry is also linked to agreeableness, extraversion and conscientiousness, so good looking people generally find it easier to make friends and hold down jobs.
It is why so many people are choosing plastic surgery to straighten noses, and even-up lopsided grins. However, biologically, they are cheating their partners, as they will still pass on their wonky genes no matter what they look like from the outside.
And the importance of symmetry does not stop at facial features.
Studies have also shown that women partnered to men with symmetrical bodies have the most orgasms, and those with symmetrical breasts are more fertile than those less evenly endowed.
Even female swallows prefer males with symmetrical tail feathers as they hunt for superior genetic quality and developmental stability.
While many women might be looking for the tell-tale signs of a wedding ring, research suggests men’s hands can reveal a whole lot more.
In recent years scientists have discovered that there is an intriguing link between finger length and the levels of testosterone that a man was exposed to while still in the womb.
That’s important because high levels of testosterone are linked to high sperm counts, increased fertility, good cardiovascular health and better genes. People with longer ring fingers are also likely to have symmetrical faces.
This one stumped even Darwin, who tried to discover why gentlemen prefer blondes, and eventually gave up, after finding there was no overall preference for the fairer sex.
The blonde hair and blue eye combination found in Caucasians is thought to have evolved among northern European tribes around 11,000 years ago.
For tribes who were venturing ever further north with the retreating ice sheets, being blonde would have bestowed an evolutionary advantage. The loss of pigmentation in the skin allows deeper penetration of ultraviolet light needed to synthesise vitamins which were essential for good health. So blondes were more likely to be healthier and live longer.
Some archaeologists suggest that it was a time of great rivalry when men were often killed and women had to compete fiercely for partners. It is thought that Palaeolithic hunters chose blondes because they stood out from their rivals and were more likely to be healthy.
Many women who are blonde go darker as they age, so blonde hair is also viewed as an indicator of youth, and sexual vitality.
And, intriguingly, Caucasian blondes usually have slightly higher oestrogen levels than brunettes and are likely to exhibit finer infantile facial features such as a smaller nose, smaller jaw, pointed chin, narrow shoulders, smooth skin and less body hair.
However a recent study which attempted to determine the most beautiful woman in the world picked a brunette. And a 2011 study in the Scandinavian Journal of Psychology, found that brunettes are generally considered more attractive.
Just as there is an ideal ratio for finger length, it seems that humans are programmed to quickly sum up the bodily measurements of a future lover.
Again these are based on genetic clues which we are unconsciously gleaning from bone ratios.
Men prefer a waist-to-hips ratio of 7:10. Hip width and breast size are important factors in fertility, child birth, and rearing, so there's definitely an evolutionary connection there.
A BMI (Body Mass Index) of 20.85 has been determined as the most attractive weight for a woman. Scarlett Johansson has previously been voted as having the most attractive female figure.
Women are unconsciously looking for a man who has a waist-to-hip ratio of 9:10 and are attracted to a partner with a big jaw, a broad chin, an imposing brow. The angle between their eyes and mouth, cheekbone prominence, and facial length all play a role as well as does facial hair. Most women prefer heavy stubble to either a beard of clean shaven. However men with full beards are viewed as better fathers.
The perfect man should also have body fat of around 12 per cent which is an important indicator of how well the immune system works.
And the limbal ring -- the area where the iris meets the white of the eye -- is thought to signal youth and health. In a 2011 study, men and women with a dark limbal ring were perceived as more attractive.
Scientists are divided about whether humans actually emit pheromones – the chemical signals secreted by animals to help find a mate – but we certainly use smell to detect how genetically compatible a partner might be.
Studies have found that we can literally sniff out our immune system match, the person whose genes complement ours, which will give us healthier babies.
In fact, the most compatible partner genetically would be the one who is the least like you. In terms of evolutionary biology it is easy to see the benefit of having one partner who is less susceptible to getting colds or flu while another has greater immunity to measles, for example.
When sniffing t-shirts saturated with men's sweat, women preferred the smells of men with high levels of testosterone, particularly when they were at peak fertility.
However research by Newcastle University has suggested that the Pill could stop women picking up these important genetic clues because it alters hormones which make the body think it is pregnant. While that stops women getting pregnant it also means they would rather be surrounded by close family members, and so are more attracted to people who are genetically similar. And for choosing a partner, that is dreadful.
Although it might seem like a good idea to stand out from the crowd when playing the mating game, new research suggests it actually pays to look average.
People with "mathematically average" features advertise a more diverse set of genes and better reproductive health, evolutionary biologists say.
"Basically what our brain does is we go around in our environment, picking up people’s faces and making the average out of these faces we see on a daily basis," Dr. Kang Lee, psychologist at the University of Toronto.
“And because of that, then, we actually have in our head... a representation of the average of the face. So there’s something we have genetically that’s driving us to prefer to look at something that’s average."
Ideally, you want the distance between your eyes and mouth to be about 36 percent of the length of your face.
And, the distance between your eyes should be 46 percent of your face's width.
The voice and mouth
Men prefer women with high, breathy voices as it signifies youth. Women’s voices tend to get lower as they age. A higher pitched voice is also thought to denote small body size.
Female listeners prefer a male voice that signals a large body size with low pitch.
Men are attracted to women who smile, but it's not true the other way around.
Research found that smiling females were rated as more attractive, whereas men showing happy emotions were rated as less attractive.