Quantitative measures of neck flexion mediate behavioural effects of postural feedback

Adopting physical expressions of emotion has been shown to have feedback effects on individuals’ mood and behaviour. For example, adopting the expansive and contractive body language of dominance and submission can affect individuals’ feelings of power, but the effects are subtle and variable. Part of this variability may stem from the high number of degrees of freedom in body language, with multiple distinct actions and muscular patterns underlying the categorical constructs of “expansive” and “contractive” postures. Using quantitative measures of body posture algorithmically derived from video recordings, we demonstrate for the first time that neck flexion fully mediates the effects of posture on mood in a postural feedback (i.e. “power posing”) paradigm; that is, adopting expansive and contractive body language affects mood by introducing variability in neck flexion. We also investigate several other mediators and moderators of postural feedback, finding that both perceived difficulty of the posture and awareness of one’s body play key roles, and identify a muscular correlate of neck flexion which correlates with mood effects. The present work carries implications for our understanding of the adaptive benefits of expansive and contractive postures, as well as substantial methodological insights for controversial research on power posing.