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Abstract Recent research suggests the potential importance of dynamic aspects (e.g. speed of onset and offset and degree of irregularity) of facial movement for the encoding of spontaneous versus deliberate emotional facial expressions. The present studies were conducted to investigate whether emotion elicited and deliberate facial expressions of happiness and disgust differ regarding their dynamic features. Two experiments were designed to elicit spontaneous and deliberate facial expressions of happiness and disgust. The experiments differed regarding the deliberate facial expressions, which were either poses (Experiment 1) or masking deceptions (Experiment 2). Experiment 2 confirmed Ekman and Friesen S (1982) notion, that spontaneous expressions have slower onsets and offsets than do deliberate expressions. The data show that dynamic aspects of the facial expressions differentiate between elicitation conditions. However, the evidence was more consistently found for the degree of irregularity of the expression than for the speed of onset and offset.
Heß et al. (1990) studied this question.