It’s all in the eyes. Sparkling blue, sea green, hazelnut — what do you find attractive? In fact, it might not be anything to do with the color of your partner’s eyes, but a dark ring that circles their iris that caught your attention.
Scientists have discovered that this circle, called a limbal ring, fluctuates in visibility and that without realizing, we use its presence to judge how healthy, and therefore attractive, a person is.
So do you have this secret signal? Take a look in the mirror. If you see a dark outline around your iris — the colored part of your eye — this is your limbal ring. It is darkest when we are at our healthiest and naturally fades with age and poor health.
Mitch Brown and Donald Sacco at the University of Southern Mississippi, Hattiesburg, wondered the extent to which limbal rings could influence the desirability of a short- and long-term partner. To find out they performed three experiments on hundreds of men and women who were asked to view images of faces that were altered to either have limbal rings or not (see image below).
In the first experiment, participants judged men and women with limbal rings as healthier — an effect that was stronger for female participants and male targets. When judging the images as a potential short-term mate, women found those with limbal rings more desirable. However, when considering which images were more desirable as a long-term partner, the presence of a limbal ring made no difference.
This makes sense, say the authors, given reproduction is a more costly endeavor for women. Evolutionarily speaking, being able to recognize health clues that may hint at who has the best genes would be advantageous when choosing a short-term partner to mate with. Likewise, being able to spot a healthy woman who offers most competition would also be advantageous. Good genes, however, are less of a priority when judging someone as a potential long-term partner.
So is there anything we can do to enhance the visibility of our limbal rings? Not really, says Brown. He says that limbal ring presence is contingent upon the clarity of the cornea — the outermost layer of the eye — which is partially predicted by the levels of phospholipids in the bloodstream.
“That’s actually what makes limbal rings such a good cue to cardiovascular health, though,” he says. “It’s very hard to fake, thus their presence can fairly reliably communicate one’s overall health”
There may be one way you can fake it temporarily, though. Contact lens manufacturer Acuvue produces disposable contact lenses with enhanced limbal rings, which they claim “make the eyes look more beautiful.”