Face Value and Cheap Talk: How Smiles Can Increase or Decrease the Credibility of Our Words.

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.