People use facial expression to help recall an emotion, for example, re-enactment of a smile helps in remembering a smile, according to a study published in Acta Psychologica.
SISSA researcher, Jenny Baumeister said, "In order to process an emotion people first reproduce the facial movements of the expression induced by that emotion. In practice, if people watch someone smiling, they tend to smile as well in order to appreciate what that person was feeling."
Researchers found that performance on the memory tasks with the face in blocked condition was significantly worse than with the face in 'free' condition. They also confirmed the hypothesis that 're-enacting' the motor pattern associated with the emotion helps to recall that emotion.