Why Monogamous and Nonmonogamous Couples Have Sex for Completely Different Reasons

Ask two people what made sex satisfying last week, and you might hear very different answers — even if they are both equally happy in their relationships. A new study published in the <em>Journal of Family Psychology</em>^[3] suggests that the gap isn't just personality or preference. It has something to do with the structure of the relationship itself. The reasons people have sex, and whether those reasons produce satisfaction, appear to follow different patterns depending on whether someone is monogamous or consensually nonmonogamous.

The study^[3], led by Emily S. Bibby and colleagues and published in August 2025, surveyed 576 young adults between the ages of 18 and 35, all of whom were in either monogamous or consensually nonmonogamous (CNM) relationships with at least one committed partner. It examined sexual communication, sexual satisfaction, and several related relational outcomes — and crucially, it looked at CNM participants across a range of relationship configurations rather than treating nonmonogamy as a single category.

The Blank Spot in the Research

For years, research on sexual satisfaction in romantic relationships defaulted to a monogamous frame. When CNM relationships entered the literature at all, studies typically compared monogamous people to nonmonogamous people as two undifferentiated groups — as if open relationships, polyamory, and swinging were variations on a single theme rather than structurally distinct arrangements with different emotional dynamics, negotiation norms, and partner hierarchies. The Bibby study notes this directly: the field has paid "little attention to various CNM styles," a gap that distorts what we think we know.

Earlier work had already begun to pull this apart. Research by Terri Conley and colleagues^[4] found that people in polyamorous or swinger-style relationships tended to report higher relationship satisfaction and stronger scores on outcomes like passionate love and trust compared to people in open relationships — a finding that dissolves the moment you lump all CNM under one label. The Bibby study extends that logic into the domain of sexual motivation and communication, asking not just whether CNM people are satisfied, but what kinds of reasons for having sex predict satisfaction within each type of relationship, including whether a partner is a primary or secondary partner within a CNM arrangement.

“The reasons people have sex, and whether those reasons produce satisfaction, appear to follow different patterns depending on whether someone is monogamous or consensually nonmonogamous.”

Motivation Isn't Universal

People have sex for a wide range of reasons — desire, intimacy, stress relief, affirmation, obligation, novelty, connection. Research in this area typically organizes those reasons into approach motives (seeking something positive) and avoidance motives (preventing something negative)^[2]. What the Bibby findings suggest is that the same motive doesn't land the same way across relationship structures. A motivation that predicts high satisfaction in a monogamous relationship may not predict the same in a polyamorous one — and within CNM relationships, the picture shifts further depending on whether sex is occurring with a primary or secondary partner.

This isn't especially surprising once you think about what relationship structure actually does. It shapes the emotional stakes of sex, the norms around initiation and refusal, the degree of security or novelty involved, and the social meaning of the act. A person having sex with a long-term primary partner is navigating a different relational context than someone having sex with a secondary partner they see once a month. The motivational logic differs. The communication needed differs. Flattening that into a single model of "sexual satisfaction" produces findings that apply accurately to almost no one.

What CNM Offers — and at What Cost

Prior research cited in the Bibby study identifies some of the distinct draws of consensual nonmonogamy^[1]: personal growth, need fulfillment, and the particular satisfactions that come from multiple committed connections. These are benefits that monogamy doesn't offer in the same form. But the same literature also documents what CNM requires: navigating social stigma, managing jealousy, and building trust across more complex relational webs. What polyamory gets wrong about jealousy is often less about the emotion itself and more about the assumption that agreements and communication can fully anticipate it.

Some benefits, the research notes, are shared across relationship types — stable partnership, love, emotional security. Others diverge. And those divergences matter for sexual satisfaction in ways that couple's therapists and sex therapists have largely been working around, because the clinical literature has historically been built on monogamous assumptions. The Bibby study's "clinical translation" is pointed: understanding the specific sexual motives associated with satisfaction in different relationship configurations could meaningfully improve how therapists approach both CNM and non-CNM couples.

Communication as the Variable That Changes

Sexual communication — the ability to express desires, negotiate boundaries, give feedback, and discuss what is and isn't working — is one of the most reliable predictors of sexual satisfaction across relationship types. But communication doesn't happen in a vacuum. It happens inside a structure that either supports or complicates it. The thing you never said is changing your relationship right now — and in CNM relationships, there are simply more things to potentially not say, more partners to potentially miscommunicate with, and more negotiated agreements that can quietly drift from what was originally meant.

This is where the Bibby study's attention to relationship configuration within CNM becomes particularly useful. Comparing a CNM person's communication with a primary partner versus a secondary partner isn't a minor methodological refinement — it's recognizing that these are functionally different relationships operating under different implicit rules and different emotional intensities. Aggregating them tells you almost nothing useful about either.

“The same motive doesn't land the same way across relationship structures — and the clinical literature has largely been built on monogamous assumptions.”

The Limits of What One Study Can Show

The study has real constraints. The sample of 576 young adults, while reasonably sized, was limited to ages 18–35, which means its findings describe a particular life stage — one characterized by relationship experimentation, identity formation, and, for many, still-developing communication skills. Whether the patterns hold for people in their 40s and 50s navigating long-term CNM arrangements or decades-long monogamous partnerships is an open question. The study also relies on self-report, which introduces the standard problems: people describe their relationships as they understand or prefer to understand them, not necessarily as they function.

The authors themselves acknowledge these limits. But even taken conservatively, the study makes a useful contribution — not by resolving the debate about which relationship structure produces more satisfaction, but by showing that the debate has been poorly framed all along. The real question isn't monogamy versus nonmonogamy. It's what conditions, within any given structure, allow people to communicate clearly about what they want and to feel that what they want actually matters.

That question turns out to have different answers depending on where you're standing inside the relationship — and the tools someone needs to get there may look quite different than a therapist trained on a monogamous default would expect.

References

1. A Narrative Review of the Dichotomy Between the Social Views of Non-Monogamy and the Experiences of Consensual Non-Monogamous People (pmc.ncbi.nlm.nih.gov)
   Documents distinct benefits of consensual nonmonogamy including personal growth, need fulfillment, and satisfactions from multiple committed connections.
2. Approach and avoidance sexual motives: Implications for personal and interpersonal well-being (onlinelibrary.wiley.com)
   Establishes the framework of approach motives versus avoidance motives used to organize reasons people have sex throughout the article.
3. Sexual communication and satisfaction in young adults' monogamous and consensually nonmonogamous relationships (pubmed.ncbi.nlm.nih.gov)
   Provides the core 2025 study data comparing sexual communication and satisfaction across 576 young adults in monogamous versus consensually nonmonogamous relationships.
4. Sexual Motivation and Satisfaction Among Consensually Non-Monogamous and Monogamous Individuals (pubmed.ncbi.nlm.nih.gov)
   Documents that polyamorous and swinger-style relationships show higher satisfaction and trust than open relationships, supporting the article's argument against treating all CNM as one category.