Role of motion signals in recognizing subtle facial expressions of emotion.

Three studies investigated the importance of movement for the recognition of subtle and intense expressions of emotion. In the first experiment, 36 facial emotion displays were duplicated in three conditions either upright or inverted in orientation. A dynamic condition addressed the perception of motion by using four still frames run together to encapsulate a moving sequence to show the expression emerging from neutral to the subtle emotion. The multi-static condition contained the same four still presented in succession, but with a visual noise mask (200 ms) between each frame to disrupt the apparent motion, whilst in the single-static condition, only the last still image (subtle expression) was presented. Results showed a significant advantage for the dynamic condition, over the single- and multi-static conditions, suggesting that motion signals provide a more accurate and robust mental representation of the expression. A second experiment demonstrated that the advantage of movement was reduced with expressions of a higher intensity, and the results of the third experiment showed that the advantage for the dynamic condition for recognizing subtle emotions was due to the motion signal rather than additional static information contained in the sequence. It is concluded that motion signals associated with the emergence of facial expressions can be a useful cue in the recognition process, especially when the expressions are subtle.