Elman and Yamamoto recruited 27 volunteers — 13 men and 14 women — and sat them at computer screens where they were randomly shown pictures of 50 healthy and attractive babies and 30 others with distinct facial irregularities such as a cleft palate or a skin condition. The volunteers were told that each picture would remain on the screen for four seconds but they could shorten that time by clicking one key or prolong it by clicking another. What the researchers wanted to learn, Elman explains, is how much effort people were willing to exert to look at pictures of pretty babies or avoid pictures of less pretty ones — and, importantly, what that implies.

Much of the answer, they found out, depends on the beholder’s sex. The men in the study were less likely than women to click off photos of unattractive babies — viewing them for the full four seconds — but clicked quite a bit to hold on to the images of the pretty ones. Their reactions were the same whether they had children of their own or not. Women, conversely, left the keyboard alone when they were looking at pretty babies but hurried away from the less attractive ones — with the results again not seeming to be influenced by whether or not they were mothers themselves.