Based on modern theories of signal evolution and animal communication, the behavioral ecology view of facial displays (BECV) reconceives our 'facial expressions of emotion' as social tools that serve as lead signs to contingent action in social negotiation. BECV offers an externalist, functionalist view of facial displays that is not bound to Western conceptions about either expressions or emotions. It easily accommodates recent findings of diversity in facial displays, their public context-dependency, and the curious but common occurrence of solitary facial behavior. Finally, BECV restores continuity of human facial behavior research with modern functional accounts of non-human communication, and provides a non-mentalistic account of facial displays well-suited to new developments in artificial intelligence and social robotics.

It has long been claimed that certain facial movements are universally perceived as emotional expressions. The critical tests of this universality thesis were conducted between 1969 and 1975 in small-scale societies in the Pacific using confirmation-based research methods. New studies conducted since 2008 have examined a wider sample of small-scale societies, including on the African and South American continents. They used more discovery-based research methods, providing an important opportunity for reevaluating the universality thesis. These new studies reveal diversity, rather than uniformity, in how perceivers make sense of facial movements, calling the universality thesis into doubt. Instead, they support a perceiver-constructed account of emotion perception that is consistent with the broader literature on perception.

Do basic emotions produce their predicted facial expressions in nonlaboratory settings? Available studies in naturalistic settings rarely test causation, but do show a surprisingly weak correlation between emotions and their predicted facial expressions. This evidence from field studies is more consistent with facial behavior having many causes, functions, and meanings, as opposed to their being fixed signals of basic emotion.

SignificanceHumans often use facial expressions to communicate social messages. However, observational studies report that people experiencing pain or orgasm produce facial expressions that are indistinguishable, which questions their role as an effective tool for communication. Here, we investigate this counterintuitive finding using a new data-driven approach to model the mental representations of facial expressions of pain and orgasm in individuals from two different cultures. Using complementary analyses, we show that representations of pain and orgasm are distinct in each culture. We also show that pain is represented with similar face movements across cultures, whereas orgasm shows differences. Our findings therefore inform understanding of the possible communicative role of facial expressions of pain and orgasm, and how culture could shape their representation.

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