Infant Smiling Dynamics and Perceived Positive Emotion.

To better understand early positive emotional expression, automated software measurements of facial action were supplemented with anatomically based manual coding. These convergent measurements were used to describe the dynamics of infant smiling and predict perceived positive emotional intensity. Over the course of infant smiles, degree of smile strength varied with degree of eye constriction (cheek raising, the Duchenne marker), which varied with degree of mouth opening. In a series of three rating studies, automated measurements of smile strength and mouth opening predicted naïve (undergraduate) observers' continuous ratings of video clips of smile sequences, as well as naïve and experienced (parent) ratings of positive emotion in still images from the sequences. An a priori measure of smile intensity combining anatomically based manual coding of both smile strength and mouth opening predicted positive emotion ratings of the still images. The findings indicate the potential of automated and fine-grained manual measurements of facial actions to describe the course of emotional expressions over time and to predict perceptions of emotional intensity.