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The evidence on universals in facial expression of emotion, renewed controversy about that evidence, and new findings on cultural differences are reviewed. New findings on the capability for voluntarily made facial expressions to generate changes in both autonomic and central nervous system activity are discussed, and possible mechanisms by which this could occur are outlined. Finally, new work which has identified how to distinguish the smile of enjoyment from other types of smiling is described.
Paul Ekman (Wed,) studied this question.