Faces synchronize when communication through spoken language is prevented.

Cooperating with another person requires communicating intentions and coordinating behavior. People often accomplish these tasks using spoken language, but verbal communication is not always available. Here, we test the hypothesis that, to establish successful cooperative interaction, people compensate for the temporary loss of one means, verbal communication, by amplifying another, namely nonverbal expressive synchrony. Fifty-seven female dyads, half of whom were prevented from using spoken language, completed four cooperative tasks, two of which induced expressions of emotion, while their faces were filmed. The no-language dyads displayed more facial-expressive synchrony, quantified using a novel application of multidimensional dynamic time warping. We find that solutions to coordinating interaction solved by spoken language can be compensated for by synchronizing facial expressions. The findings also point to one social force-the lack of shared language-that might, in the long-term, select for cultures of increased nonverbal expressiveness and synchrony. (PsycInfo Database Record (c) 2023 APA, all rights reserved).