. Author manuscript; available in PMC: 2011 Jun 1. Published in final edited form as: Emotion. 2010 Jun;10(3):433–440. doi: 10.1037/a0018690

Abstract Although it was proposed over a century ago that feedback from facial expressions influence emotional experience, tests of this hypothesis have been equivocal. Here we directly tested this facial feedback hypothesis (FFH) by comparing the impact on self-reported emotional experience of BOTOX injections (which paralyze muscles of facial expression) and a control Restylane injection (which is a cosmetic filler that does not affect facial muscles). When examined alone, BOTOX participants showed no pre- to post-treatment changes in emotional responses to our most positive and negative video clips. Between-groups comparisons, however, showed that relative to controls, BOTOX participants exhibited an overall significant decrease in the strength of emotional experience. This result was attributable to a) a pre- vs. post decrease in responses to mildly positive clips in the BOTOX group and b) an unexpected increase in responses to negative clips in the Restylane control group. These data suggest that feedback from facial expressions is not necessary for emotional experience, but may influence emotional experience in some circumstances. These findings point to specific directions for future work clarifying the expression-experience relationship. Keywords: BOTOX, Emotional Experience, Facial Expression, Facial Feedback, Embodied Emotion One of the most socially significant of human behaviors is expression of emotions on the face. Accordingly, scientific interest in facial expressions has a long history (Darwin, 1872) and is as alive today as ever (Gross, 1998; Niedenthal, 2007). Much of this interest has concerned the role of emotional expressions as social signals of internal states, and the mechanisms by which we recognize these expressions in others (e.g. Adolphs, 2002; Ekman, Friesen, & Ancoli, 2001; Olsson & Phelps, 2007).