Whereas other studies have examined effects of emotional expression on immediate emotional experience, this study investigated the more lasting influence of practised expressions.
Participants repeatedly produced the facial expressions and postures associated with either Happiness , Sadness or Anger. Subsequently, participants responsive to their bodily, personal cues felt more of the emotions they practised, even though they were no longer performing the expressive behaviour.
In a separate procedure, they recalled more life events with an emotional content associated with their training. No mood changes occurred for participants responsive to situational cues.
Do you want to be happier? It’s simply- smile.
source: “Keep smiling: Enduring effects of facial expressions and postures on emotional experience.” Conference Paper in Cognition and Emotion 17:787-797 · September 2003