Emerging Adulthood is a developmental phase associated with escalating alcohol use and peak levels of Heavy Episodic Drinking (HED). While alcohol misuse is normative at this stage, HED is associated with both short-term (i.e., unprotected sex, alcohol poisoning, sexual assault, etc.) and long-term (i.e., developing alcohol use disorder (AUD), cancer, liver disease, etc.) consequences. The role of peers in EA alcohol use is well established, but research on peer influence tends to assume homogeneity among peer relationships. It is likely, however, that romantic partners play an important and unique part in EA alcohol use above and beyond that of platonic peers. Heart rate variability (HRV), a measure of autonomic nervous system functioning linked to emotion regulation, is a sensitive biomarker of AUD processes such as craving, consumption, and relapse. Although the relevance of HRV to alcohol use has not been frequently studied among dyads or EA, separate literatures suggest that it may be of fundamental importance linking alcohol use and adaptive versus maladaptive conflict in EA. The primary objective of the proposed study is to examine sex differences in the behavioral and physiological mechanisms underlying the relationship between adaptive and maladaptive conflict behaviors and alcohol demand intensity among EA couples.