The representational momentum effect of emotional valence perception in dynamic happy expressions

The representational momentum (RM) effect of dynamic facial expressions indicates that observers tend to perceive the last frame of a dynamic facial expression as exhibiting a higher or lower emotional state than it actually does. However, the factors influencing its magnitude remain unclear. The present study investigates the impact of the emotional intensity of the last frame and the degree of change in dynamic happy expressions on the RM effect through six experiments. The results indicated that the RM effect emerged at approximately 20% or greater degrees of change. Specifically, the valence ratings are overestimated when the dynamic happy expressions transition from weak to strong, while they are underestimated when the expressions transition from strong to weak. Moreover, a greater degree of change amplifies the RM effect. When the degree of change was held constant, the emotional intensity of the last frame had opposite effects depending on the direction of change: during the emotional onset phase, a greater emotional intensity resulted in a smaller RM effect, whereas during the emotional offset phase, a greater emotional intensity led to a larger RM effect. These findings deepen our understanding of the cognitive processes involved in the perception of dynamic facial expressions.