Movie S1.

The movie illustrates the stimulus generation and task procedure using an example trial. On each trial, a dynamic face movement generator (1) randomly selected a combination of individual face movements called action units (AUs; 21) from a core set of 42 AUs (minimum = 1, maximum = 4, median = 3 AUs selected on each trial). A random movement is assigned to each AU individually using seven randomly selected temporal parameter values – onset latency, acceleration, peak amplitude, peak latency, sustainment, deceleration, and offset latency. In this example trial, four AUs are randomly selected – brow lower (AU4) color-coded in yellow, cheek raiser (AU6) color-coded in blue, nose wrinkler (AU9) color-coded in pink, and lip stretcher (AU20) color-coded in red. The randomly activated AUs are then combined to produce a random facial animation (here, ‘Stimulus trial’). Observers in each culture viewed the resulting facial animation played once for a duration of 2.25 seconds. If the random face movements matched their mental representation of a facial expression of ‘pain’ or ‘orgasm,’ they categorized it accordingly (here, ‘Pain’) and rated its intensity on a 5-point scale from ‘very weak’ to ‘very strong’ (here, ‘Strong’).

Distinct facial expressions represent pain and pleasure across cultures

Chaona Chen, Carlos Crivelli, Oliver G. B. Garrod, Philippe G. Schyns, José-Miguel Fernández-Dols, and Rachael E. Jack

PNAS. 2018. DOI: 10.1073/pnas.1807862115