Do Limbal Rings Really Enhance Beauty?

A man with an exaggerated limbal ring (eye on left of image) and a minimized limbal ring with blur to simulate the effects of ageing (eye on right). Adapted by the author.

Source: Joanna Malinowska / Freestocks

When we look at a face, the feature that tends to capture our attention is the eyes. Because of this, psychologists have long been interested in whether properties of the eye influence perceptions of attractiveness.

Studies have shown that a the white part of the eye, called the sclera, is more appealing the whiter it is—which makes sense given that a whiter sclera is associated with youth and health. Eyes that gaze toward us are more attractive than eyes that gaze to the side, probably because eye contact implies interest. And a darker periphery of the iris, also known as a limbal ring, enhances judgments of health and beauty. But why?

Since the limbal ring effect was first discovered in 2011, psychologists have speculated that it might be explained by the tendency of limbal rings to fade with age. A darker limbal ring would therefore signal youth and, perhaps, fertility.

Another plausible explanation is that a dark limbal ring makes the sclera seem whiter through a process called simultaneous brightness contrast. This is when an area with a set brightness level appears lighter when it is surrounded by a darker area, or darker when it is surrounded by a lighter area. The same effect occurs when a person wears dark eyeliner.

Putting Limbal Rings to the Test

But, as yet, the hypothesis that limbal rings make a person seem healthier and more attractive because of this simultaneous contrast effect has not been tested. Matt C. Howard of the University of South Alabama has recently taken up the call.

For a recent study, Howard selected faces of average attractiveness from the Chicago Face Database, a free set of stimulus faces. He then used photo editing software to remove limbal rings from the eyes of the faces and then reintroduce them in a controlled fashion by adding a semi-transparent black ring to the inner rims of the irises. This gave him a set of faces that were identical save for the presence or absence of limbal rings.

Then Howard lightened the sclerae of the eyes by superimposing on them a semi-transparent white layer. Now he had a set of faces with or without limbal rings and with or without lightened sclerae.

Details of stimuli in Howard's study. Top, eyes with limbal rings in experiment 2. Bottom, eyes without limbal rings and with lightened sclera in experiment 2.

Source: Howard (2026)

He showed these images to about 130 women. The women rated the faces for healthiness and attractiveness. Howard found no effect of limbal rings or sclera lightness on either measure. He wondered whether this was because his edits to the images were too subtle, and boosted them before conducting a second experiment. Again, though, he found that faces were not judged as healthier or more attractive depending on the presence of limbal rings or on sclera lightness.

He did, however, find that faces with limbal rings plus lighter sclerae were perceived as healthier than faces without limbal rings, and that faces with limbal rings and faces with lighter sclerae were perceived as similarly healthy and attractive. He interprets this as evidence that the limbal ring effect on perceptions of health and attractiveness is driven by the apparent whiteness of the sclerae.

But I’m not too sure. If limbal rings make sclerae seem lighter, the two variables are not independent in Howard’s experimental design: A lightened sclera would seem to be extra light when paired with a limbal ring, thanks to simultaneous contrast.

In his next experiment, Howard did away with sclerae entirely by presenting a new group of volunteers with pairs of irises and pupils alone, masking out the sclerae and the rest of the face. He had his volunteers rate these eyes for attractiveness and healthiness, and found no effect of limbal rings on either measure. He concludes that this experiment provides "further support that the perceptual differences are indeed because of the perceived lightening of the sclera."

Iris-only stimuli used in one of Howard's experiments

Source: Howard (2026)

But again, I remain unconvinced. In real life, we never encounter irises in isolation from the rest of a person’s face. Even when a person’s face is partially obscured, an iris can usually be seen in combination with the sclera and the skin and hair surrounding the eye. Irises in isolation appear unnatural and even a little creepy. I therefore wonder whether Howard’s null finding in this experiment may be due to his volunteers not being able to properly assess the irises’ attractiveness and healthiness.

Howard makes the valid point that most studies of the effects of limbal rings on perceptions of healthiness and beauty have reused the face stimuli created for a pioneering 2011 study by Darren Peshek and colleagues. Peshek’s method involved superimposing irises onto different faces, rather than editing the irises that belonged to each individual face.

Howard contends that this can lead to unusual combinations of iris colour and other aspects of a face’s colour. Peshek et al chose faces of above average attractiveness; Howard chose faces of average attractiveness. Howard also notes replication studies that use the same stimuli may find the same or similar results not because the effect being tested is genuine but because it depends on some quality of the stimuli, known or unknown.

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In a final experiment, Howard showed his volunteers Peshek’s stimuli. Now he found that limbal rings enhanced men’s (but not women’s) apparent healthiness and attractiveness. He argues that this means that the results of his previous experiments cannot be explained by his volunteer pool being different to those of Peshek and others, but must instead be due to differences in their stimuli. This may be correct, but it doesn’t clarify which set of stimuli is better.

Although Peshek’s image editing methods were not ideal, neither are Howard’s: The lightened sclerae in his second experiment appear, to me at least, to be artificially white and inadequately blended with the surrounding image. Howard should be applauded, however, for sharing a step-by-step guide to his method of image editing, which can be adopted and perhaps improved upon by subsequent researchers.

Howard accounts for differences in his findings when using his own versus Peshek’s stimuli by positing a threshold effect, whereby limbal rings only have an impact on face judgments when faces are especially attractive. This is a reasonable point, but one that would need to be tested in future studies. For now, at least, it remains unclear whether the limbal ring effect is genuine and, if it is, what exactly causes it.