Difficulty does not account for emotion-specific heart rate changes in the directed facial action task

Boiten (1996) used the Directed Facial Action task (a task we developed in which participants follow instructions, based on theory about how emotion is expressed in the face, to move facial muscles deliberately to produce different facial configurations) to investigate heart rate differences among six emotional configurations. Boiten's findings closely replicated ours (Levenson, Ekman, & Friesen, 1990) in terms of heart rate change, self-reported emotion, and rated difficulty during the configurations. Boiten concluded that differences in difficulty were responsible for found differences in heart rate; in contrast, we had concluded that heart rate findings could not be explained in this manner. In this paper, we argue that neither Boiten nor we did the critical analyses needed to determine whether heart rate changes were mediated in this way. Performing these analyses, we conclude that neither reported difficulty nor two other potential mediators (time required to make the facial configurations; activity of nonfacial muscles) mediated the heart rate differences that we found between emotional configurations in the Directed Facial Action task.