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Physiological Resonance and Interpretation of Emotional Expressions833One characteristic of facial emotional expressions is that they tend to be mimicked (e.g., Bornemann et al., 2012; Rymarczyk et al., 2011; Varcin et al., 2019), which is believed to help their recognition (Niedenthal, 2007; Palagi et al., 2020). Our examination of facial muscle responses revealed that happy facial expressions were not only best recognized in the current study, but also elicited the most prominent and prolonged changes: an increase in zygomaticus activity and a decrease in corrugator activity, replicating previous findings(e.g., Rymarczyk et al., 2011; Vrana & Gross, 2004). The question arises why smiles, compared to the other expressions, yielded such strong effects. In daily life, humans are constantly exposed to smiling faces, making it the most frequently observed expression (Somerville & Whalen, 2006). These smiles can have different meanings and may signal reward, dominance or affiliation (Martin et al., 2017). In line with their assumed function to create and maintain social bonds (Keltner, 1995), past research has shown that smiles are frequently reciprocated in social interactions (Hess & Bourgeois, 2010). The relevance of smiles in interpersonal bonding might therefore be one explanation for the pronounced mimicry of smiles in our study. In addition, smiles have also been found to be mimicked without the observer being directly addressed (e.g., see Mojzisch et al., 2006) These congruent facial responses have further been linked to specific neural activations in areas associated with embodiment and self-other distinction (Schilbach et al., 2008, see also Schilbach, 2015a). According to the Simulation of Smiles model (SIMS; Niedenthal et al., 2010), congruent facial responses to smiles in a non-communicative context can also be based on knowledge%u2013based simulations of the other%u2019s emotional state instead of %u2018real%u2019 emotional contagion. Given that only expressions from the same modality, i.e. the face, and with high social signaling value, i.e. a smile, elicited facial muscle responses in the current study, embodied simulation might be a plausible explanation for our EMG findings. Without necessarily evoking the experience of happiness, the simulation of smiles could potentially even have facilitated emotion recognition (however, see Holland et al., 2020).Crying is claimed to be a uniquely human behavior and linked to a complex pattern in ANS responses, with sympathetic activation being most consistently found (Bylsma et al., 2019). Another key finding of the current study is that faces with tears were perceived as emotionally intense and increased sympathetic arousal in the participants when observing these stimuli. More specifically, the addition of tears to a neutral expression resulted in a steady peak in the observers%u2019 SCL. Other