We’ve all heard the expression that “the eyes are the window to the soul.” In other words, most people agree that much information can be gleaned by simply looking into another’s eyes. For example, psychopaths are often described as having “dead eyes.” Of course, eye shape (e.g., almond eyes) and eye color also contribute to perceptions of beauty (e.g., purchasing colored contact lenses to enhance one’s attractiveness). I conducted a quick Google search for English idioms about eyes. Here are a few classic ones that cover a wide range of contexts and meanings: A roving eye; a sight for sore eyes; an eye for an eye; beauty is in the eye of the beholder; bedroom eyes; eye candy; give the evil eye; more than meets the eye; pull the wool over your eyes; see eye to eye; the apple of my eye; turn a blind eye; and mere twinkle in your father’s eye. Eyes are so important in terms of their ability to communicate that a wide range of animals have evolved eye spots as an instantiation of mimicry (e.g., to deter predatory attacks). See here for additional photos of the eye spot larval mimicry of the spicebush swallowtail.
Eyes have such communicative powers that they appear to influence our perceptions of people in unexpected ways. For example, would you be able to gauge someone’s score on a particular personality trait as a function of their eye color? This seems like a far-fetched idea in that it is difficult to imagine a priori why eye color would be linked to personality. Karel Kleisner, Lenka Priplatova, Peter Frost, and Jaroslav Flegr recently published a paper in PLoS ONE wherein they explored the relationship between eye color (brown versus blue) and perceptions of trustworthiness (measured on a 1-10 scale). Male and female participants rated photos of men and women (n = 40 each) on several dimensions including trustworthiness. The targets varied in terms of their eye color (blue or brown). The researchers also measured the targets’ facial morphology (e.g., width-to-height ratio), and they recolored the eyes of the targets (brown to blue and vice versa) and had a different group of participants rate the recolored photos. This would permit the researchers to disentangle any possible confounds between eye color and other facial features that might be linked to eye color in arriving at judgments of perceived trustworthiness. Without getting into all of the procedural and analytic details, here are a few of the key findings:
1. The correlation between eye color and perceived trustworthiness was significant (p = 0.043). In terms of directionality, brown-eyed people were viewed as more trustworthy than their blue-eyed counterparts.
2. By analyzing the perceived trustworthiness scores of the recolored photos and comparing these to the original scores, the researchers established that it was not eye color that was driving the trustworthiness effect. Thus, it would appear that brown eyes are reliably correlated with some other facial features, with the latter being the driving force behind the effect in question.
3. Men’s facial morphological features (but not women’s) were correlated to their perceived trustworthiness (p = 0.0005) and men’s eye color were correlated to their facial features (p = 0.027) but only marginally so in the case of women (p = 0.058). Brown eyes were correlated with morphological traits that promote greater trust including rounder chins and larger eyes.
Of course, the question that begs asking is why would there be a link between eye color and particular facial features that are otherwise associated with greater trust? The researchers offer several intriguing possibilities (gene linkage disequilibrium, sex linkage and sexual selection), each of which remains to be tested.
On a personal note, I have prominent green eyes. I don’t know if green implies greater or lesser trust but I can vouch that this feature has advanced me on the mating market: My wife has often proclaimed that my eyes were instrumental in her choosing me as her mate. That said both of our children do not have green eyes. Time for me to study carefully the genetic transmission of eye color and/or to invest in DNA paternity testing! ☺
As a final thought, this study puts a whole new twist on Crystal Gayle’s 1970s classic hit Don’t It Make My Brown Eyes Blue!
Reminder and announcement: Please consider following me on Twitter (@GadSaad). Also, some of you might be interested in watching my latest TED talk titled The Evolutionary Roots of Human Decision Making. I'll probably be putting up a post about it in the near future.
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