Abstract
Empathic stress, the spontaneous reproduction of psychosocial stress by mere observation, has been shown to occur between strangers, romantic partners and in mother-child dyads. However, the mechanisms by which stress is transmitted have yet to be understood. We investigated whether facial mimicry modulates the transmission of psychosocial stress. Adolescents (13-16 years old) observed their mothers or fathers (N = 77) undergo a standardized laboratory stressor. Parents' and adolescents' faces were videotaped during the stress task and dyads simultaneously provided multiple samples of subjective stress, heart rate, heart rate variability (HRV), and salivary cortisol. The degree to which adolescents mimicked their parents' facial expressions was calculated in a multi-step procedure based on windowed-cross-lagged-regressions. To integrate the correlational structure of mimicry across different facial action units (AU), an exploratory factor analysis was employed. The solution revealed a two-factor model, constructed of a positive latent factor subsuming mimicked action units associated with the act of smiling and a negative latent factor, subsuming mimicked action units used for various negative emotions. None of the stress markers were significantly associated with the extracted latent factors indexing mimicry between parents and adolescents, providing no statistically significant evidence for an association between facial mimicry and stress-transmission in the parent-adolescent dyad. Bayes Factors generally indicated moderate evidence for a lack of association with the positive and anecdotal evidence for a lack of association with negative latent mimicry factors. In conclusion, our approach to video-based mimicry calculation showed promising results in that mimicry of positive and negative emotions could be detected, albeit no evidence for a link to actual empathic stress transmission in the laboratory was found.