Arousal, valence and their relative effects on postural control.

There is mounting evidence to suggest that emotional state can influence postural control. Emotions are often qualified using dimensions such as valence (pleasantness) and arousal. While affective pictures have been used to detail the effects of valence on postural control, the influence of arousal independently, or in combination with valence, has yet to be investigated. This is an important oversight because there are multiple sensory and neuromuscular mechanisms that are known to be sensitive to arousal and to contribute to postural control. As such, the current study is the first to independently manipulate valence and arousal through affective pictures and to examine their independent effects on postural control. Subjects stood quietly for 90 s long blocks while watching affective pictures, grouped by normative ratings of arousal (high and low) and valence (pleasant and unpleasant), and during which centre of pressure (COP) and electrodermal activity (EDA) were collected. EDA and anterior-posterior COP frequency were both increased with arousal, but not by valence. The postural effects observed in this study parallel those typically seen in other highly arousing situations, such as standing at the edge of an elevated platform or during performance evaluation. Therefore, we argue that arousal is a mediator of postural control and should be considered as a potential confound when testing or diagnosing subjects in clinical or experimental settings.