Participants viewed dynamic facial expressions that moved from a neutral expression to varying degrees of angry, happy, or sad or from these emotionally expressive faces to neutral.A contrast effect was observed for expressions that moved to a neutral state. That is, a neutral expression that began as angry was rated as having a mildly positive expression, whereas the same neutral expression was rated as negatively valenced when it began with a smile. In Experiment 2, static expressions presented sequentially elicited contrast effects, but they were weaker than those following dynamic expressions. Experiment 3 assessed a broad range of facial movements across varying degrees of angry and happy expressions. We observed momentum effects for movements that ended at mildly expressive points (25% and 50% expressive). For such movements, affect ratings were higher, as if the perceived expression moved beyond their endpoint. Experiment 4 assessed sad facial expressions and found both contrast and momentum effects for dynamic expressions to and from sad faces. These findings demonstrate new and potent contextual influences on dynamic facial expressions and highlight the importance of facial movements in social-emotional communication.