As a highly social species, humans are equipped with a powerful tool for social communication—the face. Although seemingly simple, the human face can elicit multiple social perceptions due to the rich variations of its movements, morphology, and complexion. Consequently, identifying precisely what face information elicits different social perceptions is a complex empirical challenge that has largely remained beyond the reach of traditional methods. In the past decade, the emerging field of social psychophysics has developed new methods to address this challenge, with the potential to transfer psychophysical laws of social perception to the digital economy via avatars and social robots. At this exciting juncture, it is timely to review these new methodological developments. In this article, we introduce and review the foundational methodological developments of social psychophysics, present work done in the past decade that has advanced understanding of the face as a tool for social communication, and discuss the major challenges that lie ahead.

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