Can I trust your beautiful blue eyes?

Blue eyed people, can you ever really trust them?

There is an interesting new study out of the Czech Republic that asked people to rate trustworthiness of individuals based on their eye color. Let you in on a secret. Don't trust the blue eyed. 

The article is titled Trustworthy-Looking Face Meets Brown Eyes and was written by Karel Kleisner, Lenka Priplatova, Peter Frost and Jaroslav Flegr and published in the peer reviewed online journal PLOS One. I first saw the article alluded to at the Dienekes Anthropology Blog, it is also cited at Scientific American.

Dienekes has a few things to say about the study, one point which he himself discounts, relating back to a work he once read by P.G. Maxwell-Stuart on ancient color terminology, in which an argument was made that in predominantly dark-eyed peoples, light eyes, because of their rarity, may have an indirect association with glaucoma and so were perceived as being from less than perfect stock.

The conclusion of this study, people trust brown eyed faces more than blue eyed faces. But it is not the color of the eye pigmentation but the underlying facial structure that is apparently the deciding factor. But it still might pay to watch those blue eyed folk that you run in to. Just in case.

Abstract

We tested whether eye color influences perception of trustworthiness. Facial photographs of 40 female and 40 male students were rated for perceived trustworthiness. Eye color had a significant effect, the brown-eyed faces being perceived as more trustworthy than the blue-eyed ones. Geometric morphometrics, however, revealed significant correlations between eye color and face shape. Thus, face shape likewise had a significant effect on perceived trustworthiness but only for male faces, the effect for female faces not being significant. To determine whether perception of trustworthiness was being influenced primarily by eye color or by face shape, we recolored the eyes on the same male facial photos and repeated the test procedure. Eye color now had no effect on perceived trustworthiness. We concluded that although the brown-eyed faces were perceived as more trustworthy than the blue-eyed ones, it was not brown eye color per se that caused the stronger perception of trustworthiness but rather the facial features associated with brown eyes.

Citation: Kleisner K, Priplatova L, Frost P, Flegr J (2013) Trustworthy-Looking Face Meets Brown Eyes. PLoS ONE 8(1): e53285. doi:10.1371/journal.pone.0053285
Editor: Denis G. Pelli, New York University, United States of America
Received: May 1, 2012; Accepted: November 29, 2012; Published: January 9, 2013
Copyright: © 2013 Kleisner et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This research was supported by Czech Grant Agency project P407/11/1464 and by Charles University in Prague project of University Center 204004. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Figure 2. Shape changes associated with eye color and perceived trustworthiness.

Thin-plate spline visualizations of the way face shape correlates with eye color (a–f) and trustworthiness (g–i). Generated face shapes of blue-eyed woman (a) and brown-eyed woman (c) compared to average female face (b). Generated face shapes of blue-eyed man (d) and brown-eyed man (f) compared to average male face (e). Generated face shapes of untrustworthy-looking man (g) and trustworthy-looking (i) man compared to average male face (h). The TPS grids of perceived trustworthiness for women are not shown because shape analysis did not meet statistical significance. The generated facial images (a–f) were magnified 3x for better readability.

doi:10.1371/journal.pone.0053285.g002

From the introduction:

...During economic trust games, male participants with broader faces were more likely to exploit their counterparts’ trust than were male participants with narrower faces, and other players were more likely to entrust their money to males with longer and narrower faces [7]. In the human brain, the amygdala has been identified as the key structure for automatic evaluation of trustworthiness [5], [8]. Patients with bilateral amygdala damage cannot judge the trustworthiness of other persons appropriately [9]. Perceived trustworthiness also correlates with perceived happiness. Conversely, untrustworthy faces are considered to be angrier.

There is some evidence that eye color correlates with various psychological and biosocial factors, such as temperament [14]. Blue-eyed infants are reportedly more inhibited, shy, and timid than brown-eyed infants [14]–[16]. Similarly, Coplan et al. [17] found that boys with blue eyes were socially warier than boys with brown eyes, although such differences were absent between blue- and brown-eyed girls. In a previous study, we showed that eye color affects male face shape, specifically the mouth, eye, and chin area [18]. Brown-eyed males tend to have a face shape that suggests happiness and, hence, higher perceived trustworthiness while blue-eyed males tend to have a face shape that indicates anger and, hence, lower perceived trustworthiness [5], [18], [19]. There is also evidence that people are felt to be more honest if they are baby-faced with shorter chins and lower positioned features [20], [21]. Here we hypothesize that faces of brown-eyed individuals should be perceived as more trustworthy-looking than blue-eyed individuals because of certain stable facial features that correlate with eye color. Further, we wish to identify the specific features that evoke a perception of trustworthiness by using geometric morphometrics to analyze face shape variation among male and female university students.

A portion of the Discussion:

We found significant sex-dependent correlations between eye color, face shape, and perceived trustworthiness. Brown-eyed faces were perceived as more trustworthy than blue-eyed ones (See Fig. 1). There was also a relationship between eye color and face shape. Although the results were statistically significant only for male faces, the trend for female faces was in the same direction. The non-significant results for female faces might be due to lower phenotypic variability among women in general [34]. Blue-eyed male faces were characterized by a more angular and prominent lower face, a longer chin, a narrower mouth with downward-pointing corners, relatively smaller eyes, and rather distant eyebrows. This was also the pattern of an untrustworthy face. In contrast, brown-eyed faces tended to have a rounder and broader chin, a broader mouth with upward-pointing corners, relatively bigger eyes, and eyebrows closer to each other. This was also the pattern of a trustworthy face. Our findings are consistent with those of Todorov [5], i.e., when facial features associated with perceptions of higher (or lower) trustworthiness are exaggerated, the result is an expression of happiness (or anger) (See Fig. 2g–i). Further, the longer chin of blue-eyed individuals makes them look less baby-faced. It has been shown that higher ratings for honesty are given to more baby-faced people with shorter chins and lower-positioned facial features [20].

Given the negative correlation between perceived dominance and trustworthiness, our present results seemingly contradict the finding by Kleisner et al. [18] that brown-eyed men are perceived as being more dominant. It may be that eye color transmits two different signals. The perceived dominance of brown-eyed men may weaken but not totally eliminate the relationship between brown-eyed face shape and perceived trustworthiness. In support of the two-signal hypothesis, eye color had a stronger effect on trustworthiness when perceived dominance was controlled.

Our results lead to three questions. First, why would a man with a less robust face, characterized by a smaller nose, chin, and mouth, be perceived as less trustworthy? Second, why would these less robust faces be associated with blue eyes? And third, why would this association be stronger for male faces than for female faces?

Men with smaller facial features are perceived as less masculine, and therefore as less dependable and trustworthy. For instance, when Japanese women judge Japanese men, they tend to associate darker skin (itself a male characteristic) not only with greater masculinity, strength, and assertiveness, but also with manly sincerity and dependability [35]. Nevertheless, there is also evidence that more masculine faces are generally thought to be less cooperative, less honest, and less parenting-oriented [36]. Men with wider faces are perceived as less attractive and less trustworthy [7]. Keep in mind that facial WHR does correlate with various facial features that in turn correlate with perceived trustworthiness but not with eye color. The GMM analysis also showed that differences in perceived trustworthiness are not triggered solely by facial WHR. Therefore, other facial traits than facial WHR, such as the shape of the nose, the mouth, the chin, and the eye area, may primarily contribute to a perception of trustworthiness or untrustworthiness. The same facial features that make one seem more trustworthy, namely bigger eyes, larger eyebrows, a mouth with upward-pointing corners, and a generally extended and narrower face shape, are also perceived as being more attractive (see [37] for attractiveness visualization). To date, it seems that relatively smaller eyes and a smaller mouth with downward-pointing corners are the facial traits that cause the lower perceived trustworthiness of blue-eyed males.

Adaptation may also affect how one perceives the trustworthiness and attractiveness of a face [38]. The extent to which male (or female) faces are judged trustworthy (or untrustworthy) would thus depend on visual experience with a particular face shape...