Facial expressions of emotion: an old controversy and new findings.

Evidence on universals in facial expression of emotion and renewed controversy about how to interpret that evidence is discussed. New findings on the capability of voluntary facial action to generate changes in both autonomic and central nervous system activity are presented, as well as a discussion of the possible mechanisms relevant to this phenomenon. Finally, new work on the nature of smiling is reviewed which shows that it is possible to distinguish the smile when enjoyment is occurring from other types of smiling. Implications for the differences between voluntary and involuntary expression are considered.