This study aims to understand the role of the vagus nerve in promoting social bonding by using a non-invasive stimulation technique called transcutaneous vagal nerve stimulation (tVNS). The investigators will investigate whether tVNS can improve emotional, physiological, and behavioral experiences during and after social interactions. Couples will be randomly assigned to receive either tVNS or a sham stimulation during gratitude expression and problem-solving discussions. The investigators will measure their subjective evaluations of the interactions and capture their physiological and behavioral synchrony. This research will shed light on the processes involved in social connection and explore the potential of tVNS as a tool to enhance bonding in close relationships.

As fundamental as the need to belong is to human survival and functioning, decades of research have shown that social connection is critical to emotional well-being. The current investigation seeks to use the knowledge and technological advances in the biomedical field to examine the causal role of the vagus nerve in promoting social bonding. Specifically, building on the recent evidence suggesting the effects of transcutaneous vagal nerve stimulation (tVNS) on improving social cognitive functioning, this study will examine the utility of tVNS in modulating emotional, physiological, and behavioral experiences during and after social interactions. The investigators will examine if romantic couple assigned to receive tVNS vs. active sham stimulation during two types of conversations (i.e., gratitude expression and problem-solving discussion) show differences in their experiences of the interactions. The study outcomes will include subjective evaluations of the interaction (e.g., felt emotions) and their physiological synchrony. This investigation will provide insights into the mechanistic processes that undergird social connection and, importantly, be the first to examine the potential utility of tVNS as an intervention tool for promoting social bonding within close relationships.

Inclusion Criteria:

• Fluent in English
• Having been in a relationship with the partner for at least a year
• Within the age range of 18-39

Exclusion Criteria:

• Major chronic disease. self-reported autoimmune disease; severe asthma; lung disease (such as chronic bronchitis; history of stroke, heart attack, epilepsy, brain injury); cardiovascular disease.
• Cancer: if not in remission.
• Substance dependence-current or long history (5 years of more).
• Current psychiatric diagnosis that is not being treated with medication
• Confounding medications, including those used to treat hypertension and cardiovascular conditions; psychoactive substances; and medications known to directly affect autonomic functioning.

There is currently no plan to make individual participant data available to other researchers.

After excluding five individuals whose physiological data during the conflict were unavailable and one whose baseline RSA was unavailable, our final analytic sample consisted of 134 individuals.

During a <2 hour laboratory session.

As the study was short (< 2 hours), did not involve any medical procedures, and recruited healthy couples with no major chronic disease, no serious adverse events were expected to occur. Previous research using similar procedures of stimulation (of similar intensity) also suggests that adverse events are unlikely. At most, mild forms of adverse events could occur in terms of physical irritation from stimulation and were monitored. Mortality/serious adverse events were not monitored/assessed.

Participant couples will be blinded to their condition. Experimenters running the study will not be blinded since tVNS administration currently requires their knowledge of the condition.