Feel Bad and Keep Steady: Emotional Images and Words and Postural Control during Bipedal Stance

Abstract

The study investigates effects of emotional pictures and words on Center of Pressure (CoP) whole-body reactions, based on theories of emotional valence and arousal, approach–avoidance theory, freezing in humans, and stimulus type (pictures vs. words). For freezing, the study differentiated between rambling and trembling components of the CoP reaction. We hypothesized that negative versus positive emotional valence caused stronger CoP avoidance, for both emotional pictures and words. In addition, freezing was hypothesized to be evident in the CoP trembling component caused by high emotional arousal. Forty-five students enrolled in a teacher program completed a bipedal assessment on a force plate while watching positive versus negative and high- versus low-arousal pictures and words that had been selected from stimulus lists in a pretest. Participants rated the valence and arousal of all stimuli in a questionnaire, the results of which indicated a relationship between negative valence and high arousal. The force plate data confirm the hypotheses. First, negative stimuli elicited significant avoidance CoP shifts, independent of their arousal, as indicated by t tests. This effect was found for both emotional pictures and words. CoP for positive stimuli did not differ from zero. Second, indicating freezing, the CoP trembling component was increased by high arousal, independent of valence. Freezing was only found for emotional pictures. The study discusses both the CoP avoidance effect with respect to valence and stimulus type, and the value of the trembling analysis for freezing. It closes with an analysis of the methodological limitations and with recommendations for future studies.