“In 1978 psychologist John Bassili conducted an experiment in which he painted the faces and necks of several actors and actresses black and then applied one hundred luminescent dots. Participants were then asked to assume different expressions, such as ‘happy’, ‘sad’, ‘surprised’, and ‘angry’. In the final video recording, with only the luminescent dots visible, the outcome was quite revealing: while expressions of anger showed acute downward V shapes (angled eyebrows, cheeks, and chin), expressions of happiness were conveyed by expansive, outward curved patterns (arched cheeks, eyes, and mouth). In other words, happy faces resembled an expansive circle, while angry faces resembled a downward triangle.”

Lima, M. (2017)