Reasons for Sex and Relational Outcomes in Consensually Non-Monogamous and Monogamous Relationships: A Self-Determination Theory Approach

Romantic partnerships provide an opportunity for emotional and sexual fulfillment. However, having all needs fulfilled by one person can be challenging. Consensual non-monogamy (CNM) describes relationship structures where relational needs are dispersed among multiple partners, potentially decreasing pressures placed on a primary relationship. The current research investigated how self-determined sexual motives were differentially associated with sexual need satisfaction and relational outcomes in CNM and monogamous relationships. In Study One, 348 individuals from Amazon’s Mechanical Turk completed a cross-sectional survey. CNM and monogamous participants reported similar reasons for engaging in sex, though CNM participants were significantly more likely to have sex for personal intrinsic motives. No differences in mean levels of relationship and sexual satisfaction were found between CNM and monogamous individuals. Participants who engaged in sex for more self-determined reasons reported higher relational and sexual satisfaction and this relationship was mediated by sexual need fulfillment. In Study Two, 56 CNM dyads were recruited online to complete a survey on their sexual motives, need fulfillment, and relational outcomes for both a live-in partner and one additional partner. Overall, participants engaged in sex with both partners primarily for intrinsic reasons (e.g., pleasure), but reported higher mean scores with partner two for reasons such as physical intimacy and power dynamics. Structural equation modeling, guided by the actor-partner interdependence model, indicated that when individuals engaged in sex with their first partner for self-determined reasons (e.g., valuing sex), the sexual interaction was associated with meeting their own psychological needs and was thus positively related to their own relational outcomes (i.e., an actor effect), and their first partner’s relational outcomes (i.e., a partner effect). Further, having sex for self-determined reasons with a second partner, and feeling more fulfilled with a second partner, was associated with lower sexual satisfaction of the first partner. This research extends theoretical understandings of motivation within CNM relationships and highlights the importance of sexual need fulfillment in relationship wellbeing.