Effects of temporal properties of facial expressions on the perceived intensity of emotion.

A series of multiple facial expressions can be temporally perceived as an averaged facial expression in a process known as ensemble perception. This study examined the effect of temporal parameters on the perceived intensity of facial expression in each emotion, and how the effect varies with autistic traits in typically developing people. In the experiment, we presented facial expressions that switched from emotional to neutral expressions, and vice versa, for 3 s. Participants rated the overall perceived intensity of the facial emotions as a whole rather than rating individual items within the set. For the two tasks, a ratio of duration of emotional faces to duration of neutral faces (emotional ratio) and the timing for transitions were manipulated individually. The results showed that the intensity of facial emotion was perceived more strongly when the presentation ratio increased and when the emotional expression was presented last. The effects were different among the emotions (e.g. relatively weak in the anger expression). Moreover, the perceived intensity of angry expressions decreased with autistic traits. These results suggest that the properties and individual differences in the facial ensemble of each emotion affect emotional perceptions.