Nonverbal behavior and the theory of emotion: the facial feedback hypothesis.

The facial feedback hypothesis, that skeletal muscle feedback from facial expressions plays a causal role in regulating emotional experience and behavior, is an important part of several contemporary theories of emotion. A review of relevant research indicates that studies reporting support for this hypothesis have, without exception, used within-subjects designs and that therefore only a restricted version of the hypothesis has been tested. Also, the results of some of these studies must be questioned due to demand characteristics and other problems. It is suggested that visceral feedback may make a more direct contribution to emotional processes than facial feedback does and that the "readout" functions of facial expressions are more important than any feedback functions.