Postural and cardiorespiratory responses to emotionally-laden whole-body expressions

Postural and autonomic adjustments are commonly described during the observation of emotional stimuli. Thus, this study investigated the physiological impact of emotional images viewing revealed by whole-body expressions. Body sway and cardiorespiratory signals were recorded in thirty-nine healthy young people who maintained an upright stance while observing 20 neutral, 20 happiness (positive) or 20 anger (negative) images from the Bodily Expressive Action Stimulus Test (BEAST) database. Participants rated each image considering their valence and arousal dimensions with the Self-Assessment Manikin. Additionally, emotional recognition level was rated using a three alternative-forced-choice task (happiness, anger, and neutral). A repeated-measures one-way analysis of variance (ANOVA) was used to compare the main physiological variables among emotionally-laden blocks. Valence statistically differed among blocks. The emotional recognition rate was above 70 % for all blocks. There was a significant decrease in body sway area during the observation of anger whole-body expressions compared to the neutral and happiness ones. The mean power frequency in the medial-lateral axis showed a significant increase during viewing anger images compared to the neutral one. Further, there was a significant increase in the heart rate variability during observation of anger whole-body expressions compared to the happiness one. These findings revealed physiological adjustments in the observer while viewing whole-body expressions consistent with the emotional processing experience. Therefore, the observation of images depicting anger whole-body expressions led to postural and autonomic changes in agreement with defensive responses ("postural immobility").