Abstract
How do our facial expressions affect the credibility of our words? We test whether smiles, either uninhibited or inhibited, affect the credibility of a written statement. Participants viewed a confederate partner displaying a neutral expression, non-Duchenne smile, Duchenne smile, or controlled smile, paired with a written statement. Participants then made a behavioral decision based on how credible they perceived the confederate's statement to be. Compared to a neutral expression, Experiment 1 found that participants were more likely to believe the confederate's statement when it was paired with a deliberate Duchenne smile and less likely to believe the confederate's statement when it was paired with a deliberate controlled smile. Experiment 2 replicated these findings with spontaneously emitted expressions. These findings provide evidence that uninhibited facial expressions can increase the credibility accompanying statements, while inhibited ones can decrease credibility.