account for the phenomenon

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.