Just why do people get more attractive when you're drunk?

It's a fairly well-known idea that people start looking better and better the more one drinks alcohol. But is there actually a scientific reasoning behind this? It might all have to do with a little something called bilateral symmetry.

Almost all multicellular organisms exhibit some degree of symmetry - sponges are the only known exception to this. There are many different forms of symmetry, including radial, spherical, and bilateral, which is the one that humans possess. All this means is that it is possible to cut an organism in half so that one side is identical or the mirror image of the other. The different types of symmetry are determined by how many different possible ways one could create these symmetric counterparts. In humans and other organisms with bilateral symmetry, there's only one possible line of symmetry, which is known as the sagittal plane, which runs right down the vertical center of our bodies. (Obviously, we're only talking about external appearances here - our insides aren't symmetric.)

Right, so that's the quick and dirty version of what biological symmetry is. But what does that have to do with booze? Well, it's thought that we and other organisms have a strong evolutionary preference for the appearance of symmetry, and this means people who are considered attractive are often those who display a high degree of bilateral symmetry. And, as NCBI ROFL reports, researchers at London's Roehampton University hypothesized that a reduced ability to judge this symmetry brought on by the general visual impairment of alcohol might well account for the phenomenon that people seem more attractive when one is drunk. It's really that they simply seem more symmetrical - or, perhaps more accurately, less asymmetrical.

In the abstract for their paper, they discuss the experiment:

We tested the hypotheses that acute alcohol consumption decreases ability to detect asymmetry in faces and reduces preference for symmetrical faces over asymmetrical faces. Twenty images of a pair of faces and then 20 images of a single face were displayed on a computer, one at a time. Participants were instructed to state which face of each of the face pairs displayed was most attractive and then whether the single face being displayed was symmetrical or not. Data were collected near campus bars at Roehampton University. Sixty-four self-selecting students who undertook the study were classified as either sober (control) or intoxicated with alcohol. For each face pair or single face displayed, participant response was recorded and details of the alcohol consumption of participants that day were also obtained.

So what do 64 drunken and slightly less drunken Brits have to tell us about the nature of attractiveness? Here, according to the researchers, are the results:

Sober participants had a greater preference for symmetrical faces and were better at detecting whether a face was symmetrical or otherwise, supporting the hypotheses. A further, unexpected finding was that males made fewer mistakes than did females when determining whether individual faces were asymmetrical. The reduced ability of inebriated people to perceive asymmetry may be an important mechanism underlying the higher ratings of facial attractiveness they give for members of the opposite sex and hence their increased frequency of mate choice.

"Increased frequency of mate choice" has to be one of the all-time great scientific euphemisms. Anyway, while there are obviously other possible interpretations of this particular human behavior, it does seem far more interesting to explain it as a case of compromised recognition of bilateral symmetry as opposed to the previous scientific explanation, which I believe was something along the lines of "Because I was shit-faced!" Isaac Newton came up with that one, if I'm not mistaken.

Via NCBI ROFL. Image by bark on Flickr.