Human Postural Responses to Single Sound Signals with Different Emotional Content

Abstract

The listening of biologically significant sound information leads to involuntary postural preparation for the subsequent motor response. In this work, postural indices characterizing changes in the human vertical posture in response to single short biologically significant sound stimuli are investigated. In the first part of the work, a psychoacoustic experiment was performed using the International Affective Picture System in group of 46 subjects. According to its results, three sound stimuli with the duration of about 1 second were selected: two with negative content (a woman’s scream and the sound of a car brake) and one with emotionally neutral stimulus—a phone bell. In the second part of the work, the center of the pressure (CoP) of the body was recorded in response to the three stimuli in a group of 21 subjects. Analysis of the data within 8 seconds after the start of the stimulus (the time of the postural response) revealed a increase in the following stabilometric indices compared to silence: the CoP trajectory length, CoP average linear velocity and the spread along the frontal and sagittal axes, the area of the confidence ellipse. This method proved to be resistant to the variability of latency and amplitude of the postural response. According to the results obtained, short sounds that were with duration less than ones of the postural response, led to a short-term slight destabilization of the pose regardless of their emotional content. The area of the confidence ellipse has the largest changes in comparison with the other indices up to 36–39% according to the average data for different stimuli.