Posing popes: A question of left and right

Portraits of human faces, from Renaissance artworks to social media selfies, often show a so-called left cheek bias, with the left half of the face put forward more frequently. This is thought to convey emotional expressivity and warmth. A unique scientific resource to determine the temporal continuity of this phenomenon over the last centuries are the portraits of popes, as available on the official Vatican website. Data analysis of the 266 popes did not reveal a significant left cheek bias, with portraits displaying 51% leftward, 3% symmetrical, and 46% rightward bias. When dividing the portraits by every five centuries, the results showed a lack of relationship between posing bias and time period. Descriptive analysis revealed an equal distribution of right and left cheek bias in the earlier centuries, with the last five centuries presenting 60% of leftward bias. Impressively, the last 12 popes (i.e., from 1846 to 2025) had their portraits posed to the left, a phenomenon with a 0.00002% chance of occurring. We suggest that the shift in the roles played by the pope in church and society, mostly in the current and last two centuries, influenced the increased leftward bias observed in recent years.