The Effects of Exposure to Pleasant/Unpleasant stimuli on Body Posture: a Systematic Review and Meta-Analysis

Body leaning (indicating directional movements of approach or avoidance) and sway (indicating reduced mobility or freezing) are often used to assess respectively approach/avoidance and freezing in response to emotional stimuli. These responses are typically quantified using force plates that monitor the displacement of the Center of Pressure. In this article, meta-analytical analyses were conducted to synthesize findings from 44 studies (total N participants = 1756) identified from 5 databases, that manipulated the valence of stimuli displayed —pleasant, neutral, or unpleasant—and measured corresponding body sway and leaning. The analyses revealed significant heterogeneity in the reported effects across the studies. Overall, only contrasting pleasant to unpleasant conditions (vs contrasting pleasant to neutral, or unpleasant to neutral conditions) resulted in a small meta-analytical effect size. Moderating variables such as the type of design used and the duration of exposure to stimuli question the nature of the effects reported in the literature and indicate a risk of potential confounding variables. Recommendations for future studies, with an emphasis on mitigating false negative rate by ensuring a large enough sample size, are discussed.