Temporal differences in eye and mouth movements classifying facial expressions of smiles

In our previous work (S. Nishio and K. Koyama, 1997), we examined the effect of temporal differences in eye and mouth movements on classifying facial expressions of smiles. The results showed that: (a) these differences significantly influence the classification; (b) when the mouth begins moving prior to the eyes, the expressions are taken as positive; (c) when the eyes move prior to the mouth, the expressions are taken as negative; and (d) when both movements begin simultaneously, the expressions are taken as social laughter. The above results were re-examined by increasing the number of participants. Additionally, we found that when the attention of an observer is drawn to the mouth, the rate of recognizing the facial expression of smile as positive significantly increases.