The portrait of Dorian Gray: spontaneous expression of happiness is an invariant kinematic marker.

ABSTRACT: Crucial changes in the dynamical development of a facial display can characterize and distinguish spontaneous and posed facial expressions, a topic that has been poorly investigated. To assess spontaneous expressions of happiness, we presented video clips extracted from comedies showing hilarious scenes (Emotional Induction, Experiment 1) or videoclips showing smiling faces (Motor Contagion, Experiment 2). To induce posed expressions, we adopted the classic image of posed happiness from Ekman's dataset. The results showed high consistency for spontaneous expressions of happiness, characterized by reduced amplitude, speed and deceleration peaks of the smile and lower eyebrow distance compared to posed expressions, for both methods of emotion induction. Overall, we demonstrated that high-def

SUBMITTER: Straulino E 

PROVIDER: S-EPMC12330870 | biostudies-literature | 2025

REPOSITORIES: biostudies-literature