Surprise: unfolding of facial expressions.

Responses to surprising events are dynamic. We argue that initial responses are primarily driven by the unexpectedness of the surprising event and reflect an interrupted and surprised state in which the outcome does not make sense yet. Later responses, after sense-making, are more likely to incorporate the valence of the outcome itself. To identify initial and later responses to surprising stimuli, we conducted two repetition-change studies and coded the general valence of facial expressions using computerised facial coding and specific facial action using the Facial Action Coding System (FACS). Results partly supported our unfolding logic. The computerised coding showed that initial expressions to positive surprises were less positive than later expressions. Moreover, expressions to positive and negative surprises were initially similar, but after some time differentiated depending on the valence of the event. Importantly, these patterns were particularly pronounced in a subset of facially expressive participants, who also showed facial action in the FACS coding. The FACS data showed that the initial phase was characterised by limited facial action, whereas the later increase in positivity seems to be explained by smiling. Conceptual as well as methodological implications are discussed.