The Fundamentals of Sex

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Sexual desire often declines as relationships become routine and predictable.

Self-expansion involves growing through new, shared experiences that alter how you see one another.

Research links self-expansion to greater sexual desire and satisfaction.

Seeing your partner as distinct and evolving supports attraction.

Romantic relationships often begin with intense passion before settling into something that feels more predictable and routine. However, this doesn’t mean the partners have fallen out of love. It’s just that the intense spark that initially drew a couple together has faded.

Part of the reason for this is because of a decline in novelty. Research shows that we tend to experience a decrease in arousal to the same sexual stimulus over time, but that introducing something new brings it roaring back. This is precisely why sex therapists often encourage couples to try new activities together: novelty is an easy thing you can do to spice things up.

However, a powerful way to augment the effects of novelty is to incorporate it in a manner that also promotes self-expansion.

What Is Self-Expansion?

The basic idea behind the concept of self-expansion is that human beings are wired for growth. We have a fundamental drive to expand our sense of who we are, including our skills, identities, experiences, and perspectives. One of the main ways we accomplish this is through our relationships with others.

When we enter a new relationship, we gain far more than just a partner, because our partner may introduce us to all kinds of new things. For example, they might expose you to new music, books, hobbies, friends, ideas, or ways of thinking. Every single one of these things can expand your sense of self.

When this happens, it feels exciting. It’s part of what fuels that passion in the very beginning. However, it's often the case that couples experience a decline in self-expansion over time as they settle into roles and routines. And when expansion slows or even stops entirely, sexual desire typically declines.

Why Self-Expansion Fuels Sexual Desire

Self-expansion is about more than mere novelty. It’s about seeing yourself and your partner in new and different ways. This can affect passion and desire for multiple reasons:

1. It Disrupts Predictability

The stability and security of a long-term relationship may lead us to feel very safe with our partners, but it can paradoxically put a damper on eroticism. As therapist Esther Perel argues in Mating in Captivity, familiarity breeds comfort. But when we get too comfortable, we lose the sense of mystery that stimulates desire.

When you and your partner engage in new activities that are challenging or push your boundaries, you introduce uncertainty, surprise, and novelty. While that can feel exciting in and of itself, it can also change perception.

For example, let’s say you and your partner took a dance class together and you witnessed a side of them that you’ve never seen before. Maybe you didn’t know they could move so sensually or confidently. A newfound perspective like this can easily reignite attraction.

2. It Strengthens Commitment

Research has shown that people who create space for growth and expansion within their relationship tend to be more committed to one another, which makes sense. It creates a relationship context that feels enriching instead of confining.

When being with your partner makes you feel more capable, curious, or alive, you’ll be more motivated to invest in and work on the relationship, which can strengthen your connection.

The Fundamentals of Sex

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3. It Boosts Sexual Desire

Studies also show that couples who engage in self-expanding activities together report higher sexual desire. That increased desire, in turn, is linked to greater relationship satisfaction.

But how could engaging in non-sexual activities together (e.g., going on an adventure walk, taking a cooking class) affect your sex life? It’s because excitement is transferable. When we engage in novel or challenging experiences with a partner, this creates physiological arousal that can spill over into sexual arousal.

This is the classic “misattribution of arousal” effect: your racing heart during a new experience can potentially amplify how attractive your partner seems because you're attributing some of your excitement to the other person instead of the situation. In this way, you can think of adventure as a unique kind of foreplay.

4. It Deepens Emotional Intimacy

Self-expansion isn’t just about the activities we're engaging in. It’s also about vulnerability, because trying new things together can prompt self-disclosure. For example, it might lead one of you to disclose an unspoken desire or hidden fear.

As you explore new ground together and incorporate these new perspectives and experiences into your sense of self, that creates the kind of conditions under which intimacy grows, which may also lead to more desire.

How to Harness the Power of Self-Expansion

Incorporating self-expansion doesn't mean you have to completely change your life. It can be done in relatively small ways that ultimately make a big difference.

Try Something Slightly Uncomfortable

Keep in mind that the key to self-expansion isn’t just novelty, it’s growth. This means that it's important to choose activities that push your limits a little. For instance, this could potentially include taking a class neither of you has ever tried before, traveling to a new or unfamiliar place, sharing or acting on a sexual fantasy, or initiating sex in a completely different way. Regardless of the activity, the goal is to try something new where there's the opportunity to see each other in a new light.

Work Toward a Shared Goal

Self-expansion doesn't just have to involve one-and-done kinds of things, like taking a class or a trip. For example, you might train for a mini marathon together, learn a language together, or work on some type of art project together. A larger, recurring activity that involves shared effort can help to create shared identity.

Support Individual Growth

I know this might sound counterintuitive because we just spent a lot of time talking about the importance of doing things together, but it’s also important to support one another’s individuality. Having a little bit of distance and some space to be yourself is also really important for desire.

When your partner develops interests, passions, or hobbies outside the relationship, it creates the opportunity to see them as a distinct person, not just an extension of you. Support each other's individual pursuits because having that little bit of mystery or otherness can spark desire.

Communicate Along the Way

As you continue your journey of self-expansion, it's also important to talk about your experiences, as well as how each of you are changing. For example, what are you curious about exploring in the bedroom these days? Do you want something new or different than you used to?

You might discover that what turns you (or your partner) on now isn’t the same as it was a few years ago. Our desires evolve, which is why sharing them should be an ongoing thing.

In long-term relationships, it's common for desire to fade. The culprit isn't necessarily lost lust, but stalled growth. Self-expansion is one of the keys to preventing our relationships from stagnating. It keeps partners curious about one another, it creates opportunities for surprise, and it offers a way to continuously renew attraction and deepen connection.

To keep the spark alive, focus on growth. Try new things, reveal vulnerabilities, and don’t be afraid to rewrite the script. When self-expansion happens, desire often follows.

Prekatsounaki, S., Janssen, E., & Enzlin, P. (2019). In search of desire: The role of intimacy, celebrated otherness, and object-of-desire affirmation in sexual desire in women. Journal of Sex & Marital Therapy, 45(5), 414–423. https://doi.org/10.1080/0092623X.2018.1549633

Perel, E. (2007). Mating in captivity: unlocking erotic intelligence (1st Harper pbk.). Harper.

Aron, Arthur, & Aron, Elaine (1986). Love and the expansion of self: Understanding attraction and satisfaction.Hemisphere Pub. Corp.

Hughes, E. K., Slotter, E. B., & Emery, L. F. (2023). Expanding me, loving us: self-expansion preferences, experiences, and romantic relationship commitment. Self and Identity, 22(2), 227–246. https://doi.org/10.1080/15298868.2022.2074092

Muise, A., Harasymchuk, C., Day, L. C., Bacev-Giles, C., Gere, J., & Impett, E. A. (2019). Broadening your horizons: Self-expanding activities promote desire and satisfaction in established romantic relationships. Journal of Personality and Social Psychology, 116(2), 237–258. https://doi.org/10.1037/pspi0000148

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