The Influence of Reward on Facial Mimicry: No Evidence for a Significant Effect of Oxytocin

The Reward-Related Shift of Emotional Contagion from the Observer's Perspective Correlates to Their Intimacy with the Expresser

Although previous studies have found a bidirectional relationship between emotional contagion and reward, there is insufficient research to prove the effect of reward on the social function of emotional contagion. To explore this issue, the current study used electroencephalography (EEG) and the interactive way in which the expresser played games to help participants obtain reward outcomes. The results demonstrated a significant correlation between changes in emotional contagion and closeness, indicating that emotional contagion has a social regulatory function. Regarding the impact of reward outcomes, the results showed that compared to the context of a loss, in the context of a win, participants' closeness toward the expresser shifted to a more intimate level, their emotional contagion changed in a more positive direction, and the activity of the late positive component (LPC) of the event-related potentials (ERPs) changed to a greater extent. Significantly, the mediation results demonstrated the effect of reward and indicated that changes in the LPC elicited while experiencing the expressers' emotion predicted the subsequent shifts in closeness through alterations in emotional contagion of the anger emotion in the winning context and the happy emotion in the loss context. This study provides empirical evidence regarding the social function of emotional contagion and proves for the first time that the reward context plays a role in it.

The effect of intranasal oxytocin on social reward processing in humans: a systematic review

Understanding the neurobiology of social reward processing is fundamental, holding promises for reducing maladaptive/dysfunctional social behaviors and boosting the benefits associated with a healthy social life. Current research shows that processing of social (vs. non-social) rewards may be driven by oxytocinergic signaling. However, studies in humans often led to mixed results. This review aimed to systematically summarize available experimental results that assessed the modulation of social reward processing by intranasal oxytocin (IN-OXY) administration in humans. The literature search yielded 385 results, of which 19 studies were included in the qualitative synthesis. The effects of IN-OXY on subjective, behavioral, and (neuro)physiological output variables are discussed in relation to moderating variables-reward phase, reward type, onset and dosage, participants' sex/gender, and clinical condition. Results indicate that IN-OXY is mostly effective during the consumption ("liking") of social rewards. These effects are likely exerted by modulating the activity of the prefrontal cortex, insula, precuneus, anterior cingulate cortex, amygdala, and striatum. Finally, we provide suggestions for designing future oxytocin studies.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021278945, identifier CRD42021278945.

Only empathy-related traits, not being mimicked or endorphin release, influence social closeness and prosocial behavior

Seminal studies suggest that being mimicked increases experienced social closeness and prosocial behavior to a mimicking confederate (i.e., interaction partner). Here we reexamine these results by considering the role of empathy-related traits, an indirect proxy for endorphin uptake, and their combined effects as an explanation for these results. 180 female participants were mimicked or anti-mimicked in an interaction with a confederate. The effects of being mimicked versus anti-mimicked in relation to empathy-related traits and endorphin release (assessed indirectly via pain tolerance) on experienced closeness and prosocial behavior were assessed using Bayesian analyses. Our results suggest that high individual empathy-related traits increase social closeness to the anti-mimicking and mimicking confederate and to one's romantic partner, as compared to mimicry alone. Results furthermore strongly suggest that high individual empathy-related traits increase prosocial behavior (donations and willingness to help) as compared to mimicry alone. These findings extend previous work by highlighting that empathy-related traits are more influential in creating positive effects on social closeness and prosocial behavior than a one-shot mimicking encounter.

Frequency-Tagging EEG of Superimposed Social and Non-Social Visual Stimulation Streams Provides No Support for Social Salience Enhancement after Intranasal Oxytocin Administration

The social salience hypothesis proposes that the neuropeptide oxytocin (OT) can impact human social behavior by modulating the salience of social cues. Here, frequency-tagging EEG was used to quantify the neural responses to social versus non-social stimuli while administering a single dose of OT (24 IU) versus placebo treatment. Specifically, two streams of faces and houses were superimposed on one another, with each stream of stimuli tagged with a particular presentation rate (i.e., 6 and 7.5 Hz or vice versa). These distinctive frequency tags allowed unambiguously disentangling and objectively quantifying the respective neural responses elicited by the different streams of stimuli. This study involved a double-blind, placebo-controlled, cross-over trial with 31 healthy adult men. Based on four trials of 60 s, we detected robust frequency-tagged neural responses in each individual, with entrainment to faces being more pronounced in lateral occipito-temporal regions and entrainment to houses being focused in medial occipital regions. However, contrary to our expectation, a single dose of OT did not modulate these stimulus-driven neural responses, not in terms of enhanced social processing nor in terms of generally enhanced information salience. Bayesian analyses formally confirmed these null findings. Possibly, the baseline ceiling level performance of these neurotypical adult participants as well as the personal irrelevance of the applied stimulation streams might have hindered the observation of any OT effect.

Oxytocin system gene methylation is associated with empathic responses towards children

Empathy is an essential component of sensitive caregiving behavior, which in turn is an important predictor of children's healthy social-emotional development. The oxytocin (OXT) system plays a key role in promoting sensitive parenting and empathy. In this study, we investigated how OXT system gene methylation was associated with empathic processes in nulliparous women (M age = 23.60, SD =0.44)-measuring both physiological facial muscle responses and ratings of compassion and positive affect to affective images depicting children. Linear mixed effects analyses demonstrated that lower methylation levels in the OXT and OXTR genes were related to enhanced empathic responses. The effect of OXT system gene methylation on empathic processes was partly qualified by an interaction with individual variations in women's care motivation. Our findings provide experimental evidence for an association between the methylation of OXT system genes and empathy.