EMBARGOED UNTIL 12 October 2020, 10am UK time
Both old wives’ tales and psychological literature posit that spouses’ faces become more similar over time. Scholars have argued that partners tend to occupy the same environments, engage in the same activities, eat the same food, and mimic each other’s emotions—and as these factors can also influence facial appearance—their faces should converge with time. For example, if the partners smile a lot—and make each other smile—they should co-develop similar smile lines.
Surprisingly, this widely accepted belief is supported by a single 1987 study of 12 couples, whose results have never been replicated. In their paper, Pin Pin Tea-makorn and Michal Kosinski, of Stanford’s Graduate School of Business, examined this widely held belief in a large sample of 517 couples. Using facial images taken at the beginning of the marriage and 20 to 69 years later and two independent methods of estimating facial similarity (human judgment and a state-of-the-art facial recognition algorithm), they showed that while spouses’ faces tend to be similar at the beginning of marriage, they do not converge over time (See Figure 1 below).
Pin Pin Tea-makorn (PhD student at Stanford’s department of Electrical Engineering): “When we started this project, I was convinced that we will easily find evidence for the convergence in facial appearance. This is one of those theories that all undergrads learn in their Psych 101. Also, it sounds rather intuitive: Spouses tend to spend much time together, have similar hobbies and diet, so it is to be expected that they should grow more alike with time. Nevertheless, we were surprised that despite using a very large sample of facial images and very sensitive measurements of facial similarity, we could not find any evidence for convergence.”
Dr Michal Kosinski (Associate Professor of Organizational Behaviour at Stanford’s Graduate School of Business): “I think that scholars should spend more time validating widespread psychological theories. Many are based on scanty evidence and studies that would not be considered appropriate today. Much of what we are teaching to students, business leaders and policymakers is based on rather weak evidence. Now, rejecting widely accepted hypotheses is surely not as exciting or as news-worthy as coming up with new fancy theories, it is as, if not more, important.”
Figure 1: The average facial similarity of the spouses at marriage and 20 to 69 years later estimated using the facial recognition algorithm. Error bars represent 95% confidence intervals.