Current Biology
Volume 24, Issue 2, 20 January 2014, Pages 187-192
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Dynamic Facial Expressions of Emotion Transmit an Evolving Hierarchy of Signals over Time

https://doi.org/10.1016/j.cub.2013.11.064Get rights and content
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Highlights

  • Dynamic facial expressions transmit hierarchical information over time

  • Signals evolve from few biologically basic to complex socially specific information

  • Signaling dynamics supports discrimination of four then six emotion categories

  • Our data suggest that basic emotion communication comprises four (not six) categories

Summary

Designed by biological [1, 2] and social [3] evolutionary pressures, facial expressions of emotion comprise specific facial movements [4, 5, 6, 7, 8] to support a near-optimal system of signaling and decoding [9, 10]. Although highly dynamical [11, 12], little is known about the form and function of facial expression temporal dynamics. Do facial expressions transmit diagnostic signals simultaneously to optimize categorization of the six classic emotions, or sequentially to support a more complex communication system of successive categorizations over time? Our data support the latter. Using a combination of perceptual expectation modeling [13, 14, 15], information theory [16, 17], and Bayesian classifiers, we show that dynamic facial expressions of emotion transmit an evolving hierarchy of “biologically basic to socially specific” information over time. Early in the signaling dynamics, facial expressions systematically transmit few, biologically rooted face signals [1] supporting the categorization of fewer elementary categories (e.g., approach/avoidance). Later transmissions comprise more complex signals that support categorization of a larger number of socially specific categories (i.e., the six classic emotions). Here, we show that dynamic facial expressions of emotion provide a sophisticated signaling system, questioning the widely accepted notion that emotion communication is comprised of six basic (i.e., psychologically irreducible) categories [18], and instead suggesting four.

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