Here’s a photo from my modelling portfolio:
I know what you’re thinking, why would anybody waste such good looks on a career in science? But not everybody will have had the same thought. Physical attraction is a notoriously fickle beast, one that varies across cultures and individuals. And there is a science behind it, a set of innate predispositions that bias us towards certain features and, perhaps, towards that special someone.
So what pushes your buttons, according to scientists?
#1 They have the same eyes as you (but only if you’re a blue-eyed male)
I’ve watched Up in the Air enough times to know that a pair of dreamy eyes can be decisive in how attractive we deem a face. With this idea in mind, a team of Norwegian scientists decided to put our eyes to the test. They asked volunteers to rate the attractiveness (on a scale of 1 to 5) of various human faces. But there was a twist: the eyes in many of the photos had been digitally manipulated, so that brown eyes became blue eyes, and vice versa. So how does eye colour affect how attractive you find a person?
Not at all.
That is, if you’re a woman, or a brown-eyed male. The same can’t be said for blue-eyed males, who most emphatically favoured women with blue eyes.
There’s a very intuitive reason for why blue-eyed males might be so picky. Blue eyes are a recessive inherited trait, so two blue-eyed parents will almost always have blue-eyed kids. If a brown-eyed child pops up in such a pairing, Father has every right to be suspicious (although it’s not quite fool-proof).
So this eye colour preference may have evolved to detect and discourage infidelity. Evolution trusts no one.
#2 They smell different to you
When it comes to attraction, smell matters. A surprisingly large number of sadistic researchers have asked volunteers to sniff sweat-stained garments and rate the pleasantness of each whiff. And not just for the fun of it.
Body odour can tell us a lot about a person, like their recent exercise history or preference for personal hygiene products. But it can also tell us a thing or two about their immune systems. Our bodies contain these protein complexes called human leukocyte antigens (HLA), which help control the immune system. The more different HLAs you have, the better, because then your immune system can respond to a greater range of biological threats.
Ideally, we should be mating with partners whose HLAs are different to our own, allowing our children to get the widest range of immunities possible. And that’s what has been found, in both males and females: we tend to find most attractive the odours of people with very dissimilar HLA profiles.
We’re still not quite sure how these HLA proteins manage to influence our body odour, nor how potential partners are able to pick up on it, but rest assured that scientists are working on the question (and loving every moment).
#3 They look like your parents
You’re not going to like this one. You’re really not.
In a study published in 2010, two American researchers asked subjects to rate the attractiveness of human faces. The photos shown were of complete strangers, but, in some cases, these faces were preceded by a split-second flash of the subjects’ own parent. The volunteers, who were unaware of the subliminal image, rated faces as more attractive when they were coupled with that of their mother or father.
And that’s not all. Several studies of married couples have reported that women tend to choose husbands who resemble their own fathers, and the same goes for men and their mothers. These similarities even hold up when comparing men to their wives’ adopted fathers.
Why should this be the case?
It’s certainly possible that mate preference is passed down genetically from parent to offspring: your father obviously approved of your mother’s features, and so you inherit a disposition towards those same features. This effect has been well documented in some animal species, but, alas, I had a hard time finding scientific support for its effect in humans.
More likely, according to our American researchers, is that we become attracted to the traits of those we grew up with, whether they’re actually related to us or not. Mind you, we’re not attracted to those people specifically – but to others who happen to share similar features.
But this section of the blog comes with a caveat; there’s still plenty of debate going on. While researching this topic, I noticed that the scientific literature is divided into two warring factions: some believe in sexual imprinting, as we discussed above, and others believe in the opposite Westermarck effect – that, to escape inbreeding, we’ve actually evolved to avoid people who resemble close relatives.
So the question is still up in the air. But next time you’re with your partner, leaning in for that passionate embrace, stop and study them for a moment. I mean, really study their features. Remind you of anyone?
Now good luck with that.
Andrew Katsis is an MSc candidate in Zoology at the University of Melbourne. Once you’ve gotten past the attraction phase in your relationship, click here to explore the bewildering origin and functions of human kissing.