Spouses’ faces are similar but do not become more similar 20-69 years later

Spouses’ faces are similar but do not become more similar with time. Pin Pin Tea‑makorn & Michal Kosinski. Scientific Reports, Oct 12 2020. https://doi.org/10.1038/s41598-020-73971-8

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 fndings 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.

Discussion

We do not fnd support for the widely disseminated convergence in physical appearance hypothesis: Spouses’ faces are similar but do not converge with time. Tis brings facial appearance in line with other traits—such as interests, personality, intelligence, attitudes, values, and well-being—which show initial similarity but do not converge over time.

This study has several limitations. First, we used publicly available images and thus could not control for variance in image properties and self-presentation (such as grooming, facial expression, or biases in selecting images to be publicly shared online). Yet, according to the convergence in physical appearance hypothesis, these factors should amplify the convergence rather than obscure it. Spouses’ tendency to occupy the same environments, engage in the same activities, eat the same food, and—in particular—mimic each other’s emotional expressions should result in convergence in their self-presentation behaviors, and thus more (and not less) similar public facial images. Second, we did not record or control for judges’ age and ethnicity and thus the extent to which their judgments might have been afected by the own-age36 and own-ethnicity37 biases (people’s lower sensitivity when judging the similarity of faces of other ages and ethnic groups). Yet, while the own-ethnicity bias could add noise to our measurements, it is unlikely to moderate the change in similarity over time, as participants’ ethnicity was constant. Also, while the U.S. AMT workers tend to be young38, they were as good at ranking the similarity of faces of young people (taken several decades ago) as the faces of older people (taken more recently). Furthermore, those and other risks to the judges’ accuracy were counterbalanced by the use of two independent measures of facial similarity (human judges and VGGFace2) and the relatively large sample size, enabling the detection of a change in human rankings as small as Δ=0.17 (with 80% power, α=0.001), an equivalent of one in six judges increasing a spouse’s rank by just one position. Finally, the validity of our approach and dataset are supported by the successful replication of the well-established efect of people’s tendency to marry similar others (i.e., homogamy).

While the rejection of the convergence in physical appearance hypothesis is surely not as exciting or as citeworthy as its counterfactual, it solves one of the major conundrums of psychological science and brings us closer to understanding factors predisposing people to form and maintain long-term romantic relationships.