Verified by 
During conversation, we focus on the eyes of others. We use our eyes to communicate our feelings and our interest. But surprisingly little research has been conducted into how eyes are implicated in attraction, at least compared to the heaps of research into the attractiveness of the face, the voice, and even body odor.
You may have heard about the effects of a large, dilated pupil on attractiveness. When people are aroused, their pupils, the black circle at the center of the eye, become larger. This signal of arousal is found attractive, particularly to men, but also to women, even when we don’t consciously notice it.
The white part of the eye, the sclera, is also implicated in judgments of attractiveness and health. Research shows that people with whiter rather than redder sclerata are rated as 25 percent happier, 42 percent healthier, and 17 percent more attractive.
The Limbal Ring
But what about the last of the three main parts of the eye, the colored iris? In 2011, Darren Peshek and colleagues from the University of California at Irvine ran a study in which they tampered with the limbal ring: the slightly darker ring that runs around the outside of most people’s irises. If you’ve got dark eyes, it might be difficult to spot, but those of you with blue or green eyes should be able to see that the edge of your iris, where it meets the sclera, is somewhat darker than the inside of your iris.
Peshek showed his 45 participants a set of 80 pairs of faces. The faces in each pair were identical, except for the fact that one had a darkened limbal ring, and the other had an iris of a uniform color. He found that both men and women preferred the faces with the dark limbal ring.
Recently, a new study about limbal rings was conducted by a team of researchers at the University of Southern Mississippi. Mitch Brown and Donald Sacco used the same images as Peshek — faces with exaggerated or diminished limbal rings.
In Brown and Sacco’s study, a group of 150 men and women looked at both the original photographs and the versions with the enhanced limbal rings. Each of the volunteers rated the faces for healthiness on a 7-point scale. The results showed that darker limbal rings did indeed make a face seem healthier.
However, the effect of the limbal rings on apparent health depended on the sex of the beholder and the beheld. Women thought faces with dark limbal rings were more healthy than those without, but male raters couldn’t see the difference: Men rated faces with and without limbal rings equally healthy. And what about the sex of the faces themselves? Women’s apparent health was unaffected by their limbal rings. Men, though, appeared healthier with limbal rings than without.
The Limbal Ring and Health
Why are limbal rings so important when it comes to judging health and attractiveness? Well, our limbal rings are darker when we’re young, and fade and blur as we age. Limbal rings may also be an indicator of the health of a person’s heart and circulatory system because they are darker in those who have low levels of phospholipid accumulation — a risk factor for cardiovascular disease.
Further studies by Brown and Sacco revealed that priming women to think about romantic relationships makes them rate a man without limbal rings as less healthy and that women find a dark limbal ring more attractive when judging men for a casual hookup rather than a long-term relationship.
References
Brown, M., & Sacco, D. F. (in press). Put a (limbal) ring on it: Women perceive men’s limbal rings as a health cue in short-term mating domains. Personality and Social Psychology Bulletin.
Caryl, P. G., Bean, J. E., Smallwood, E. B., Barron, J. C., Tully, L., & Allerhand, M. (2009). Women's preference for male pupil-size: Effects of conception risk, sociosexuality and relationship status. Personality and Individual Differences, 46(4), 503-508.
Lick, D. J., Cortland, C. I., & Johnson, K. L. (in press). The pupils are the windows to sexuality: Pupil dilation as a visual cue to others’ sexual interest. Evolution and Human Behavior.
Peshek, D., Semmeknejad, N., Hoffman, D., & Foley, P. (2011). Preliminary evidence that the limbal ring influences facial attractiveness. Evolutionary Psychology, 9(2), 137–146.
Provine, R. R., Cabrera, M., Brocato, N. W., & Krosnowski, K. A. (2011). When the whites of the eyes are red: A uniquely human cue. Ethology, 117(5), 395–399.
