been consistently found to increase during exposure to

stimuli rated as unpleasant or during the reported

experience of unpleasant affect. Conversely, activity of

the zygomatic major has been found to increase during the

report of positive emotional states.

Facial and Autonomic Studies

 Few studies have included measures of both facial and

 autonomic responding. In one study of affective slides

 viewing, Greenwald, Cook, and Lang (1989) examined emotional

 ratings, HR, SCR, zygomatic and corrugator EMG. Zygomatic

 activity was positively related to pleasure ratings and

 corrugator activity was negatively related. Zygomatic EMG,

 however, also increased during unpleasant slides viewing.

 Neither muscle site was related to arousal ratings. Phasic

 HR acceleration was positively related to valence ratings,

 but not arousal. This relationship was weaker than the

 valence/EMG relationship. Skin conductance responses were

 significantly related to increased arousal ratings, but not

 valence ratings. Quite similar results were found when

 autonomic and facial responding were measured during imagery

 (York, 1991; Bradley, Lang, & Cuthbert (1991) in that HR

 acceleration and SCR were larger for pleasant and unpleasant

 compared to neutral imagery, and corrugator EMG was higher

 for the unpleasant compared to pleasant and neutral imagery.

 Ekman and colleagues have found that giving subjects

either muscle-by-muscle instructions to contract voluntary