Angry and happy expressions affect forward gait initiation only when task relevant

Whole-body movements represent an ecologically valid model for assessing the effect of emotional stimuli valence on approach/avoidance reactions as they entail a change of the physical distance between such stimuli and the self. However, research in this field has provided inconsistent results as the task relevance of the emotional content of the stimuli was not properly controlled, and very often, it is impossible to dissociate the effect of arousal from that of valence. To overcome these limitations, we studied the effect of facial emotional expressions (anger and happiness) on forward gait initiation using an experimental paradigm that allows us to compare the impact of the stimuli emotional content when they are task relevant and when they are not. We found that angry and happy expressions altered forward gait initiation parameters differently only when relevant for ongoing goals. In particular, both the reaction times and the percentages of omission errors increased when the go signal was an angry face compared to when the go signal was a happy face. These results indicate that forward step movements share the same features as reaching arm movements regarding emotional stimuli, that is, facial emotions do not automatically influence behavioral responses. Instead, their effects depend critically on their conscious appraisal.