Abstract

The relative importance of dynamic and static emotion signals from facial expressions was evaluated using a temporal two-interval forced-choice paradigm.  Stimuli were black and white images of faces with a happy or fearful expression. A range of signal strengths (0-100%) of expressions were created by morphing neutral and expressive images. Dynamic stimuli were generated using a sequence of frames each containing an increasingly expressive image. One interval contained the comparison face (50%) and the other contained the test face (varied from 20% – 100%).  Observers indicated the interval that contained the image that was more expressive.  The percentage of times the test face was judged as more expressive increased as signal strength increased.

Psychometric functions describing performance with dynamic fearful stimuli are shifted to the left of functions describing dynamic happy stimuli.  This suggests that emotion signals conveyed by dynamic fearful faces are more salient than signals conveyed by dynamic happy faces.  Dynamic stimuli with a fast rate of change at stimulus onset (fast) are shifted to the left of those with a slow rate of change (slow). This suggests that ‘fast’ dynamic stimuli are more salient than ‘slow’ dynamic stimuli. Static fearful and static happy emotion signals are equally salient.