How We Perceive Others Resembling Us

Eye contact is essential for social cognition, acting as an important tool for social communication. While differences in face scanning patterns concerning familiarity have been thoroughly investigated, the impact of facial similarity on gaze behavior has not been examined yet. We addressed this topic by recording subjects’ eye-directed gazing while looking at faces that were individually created systematically varying in terms of similarity to the self-face and familiarity. Subjects’ self-faces were morphed into three other faces including a close friend of the same sex. Afterwards, they rated similarity to their self-face of those morphed face stimuli in a separate rating task. Our results show a general preference for the eyes’ area as well as differences regarding fixation patterns depending on similarity to the self-face. The lower the similarity to the self-face, the more fixations on the eyes’ area. Subjects’ ratings followed a linear line, indicating well-pronounced face perception. Nevertheless, other faces were rated faster than the self-face independent of familiarity, while morphed faces got the slowest ratings. Our results mirror the importance of similarity to the self-face as a factor shaping the way we look at the eyes of others explaining variance apart from familiarity.

Spouses’ faces are similar but do not become more similar with time

The widely disseminated convergence in physical appearance hypothesis posits that long-term partners’ facial appearance converges with time due to their shared environment, emotional mimicry, and synchronized activities. Although plausible, this hypothesis is incompatible with empirical findings pertaining to a wide range of other traits—such as personality, intelligence, attitudes, values, and well-being—in which partners show initial similarity but do not converge over time. We solve this conundrum by reexamining this hypothesis using the facial images of 517 couples taken at the beginning of their marriages and 20 to 69 years later. Using two independent methods of estimating their facial similarity (human judgment and a facial recognition algorithm), we show that while spouses’ faces tend to be similar at the beginning of marriage, they do not converge over time, bringing facial appearance in line with other personal characteristics.

Kin recognition and perceived facial similarity

Kinship and facial self-resemblance evoke similar patterns of behaviour, such as increased pro-sociality and decreased sexual motivation. Moreover, it has been suggested that facial resemblance/similarity between individuals informs kinship judgments in third-party kin recognition as one study found that similarity and kinship judgments encapsulate the same information (Maloney & Dal Martello, 2006). Yet, another study found that similarity judgments convey some information that is not conveyed in kinship judgments when comparing adult face pairs of different sex (DeBruine et al., 2009). We replicated these studies to further investigate these convergent results and clarify the role facial similarity plays in third-party kin recognition. We recruited 318 raters, who were shown 50 sibling pairs and 50 age- and sex-matched unrelated pairs ranging from 3 to 17 years old. Each rater was randomly assigned to make either kinship judgments (“related” or “unrelated”) or similarity judgments (scale from 0-“not very similar” to 10-“very similar”). We found that performance in both tasks was equally accurate, with participants detecting child siblings in the kinship task above chance and giving significantly higher similarity ratings to siblings in the similarity task. In both tasks, opposite-sex siblings were less often perceived to be siblings less often than same-sex siblings, while judgments of unrelated face pairs were not affected by the sex of faces. In contrast, the effect of difference in age between pairs of faces differed for the two tasks: in the similarity task, sibling pairs’ similarity decreased with increasing age differences, while no such effect was observed for unrelated pairs. In the kinship task, an increasing age difference decreased relatedness judgments for both related and unrelated pairs. In line with DeBruine et al. (2009), these findings suggest that similarity and kinship judgments are highly correlated but not strictly synonymous. The OSF Pre-registration for this project can be found at osf.io/ps9hy and the data and code at osf.io/sef9k.