What happens when your partner wants to have sex, but you’re just not in the mood? Should you do it anyway to please him or her? Or is no sex better than sex for the “wrong reasons”? Recent studies led by Amy Muise, PhD, a researcher who specializes in human sexuality, offer helpful insights. Here, she answers some questions on her latest research…

You study sexual motivation.What role does motivation play in a couple’s sex life? It’s well-known that couples who have more and better sex are happier. But our research shows that what motivates couples to have sex—the reasons they have it—also has a major impact on relationship satisfaction.

In one study, we gave 108 dating couples questionnaires to fill out every night for several weeks, and in another study, we gave the questionnaires to 44 couples who were married or living together. In both groups, participants rated themselves more sexually satisfied and happier in their relationships when they had sex for what we term “approach goals” than when they had sex for so-called “avoidance goals.”

Approach goals include having sex to pursue a positive outcome, such as pleasure or greater closeness, for yourself and/or your partner. Avoidance goals include avoiding a negative outcome for yourself, such as feeling guilty about saying no to sex…or avoiding conflict or disappointing your partner.

What’s more, we found that a person’s reason for having sex affected his or her partner’s feelings, too. When an individual’s motivation was positive, the partner felt more desire and relationship satisfaction than when it was negative.

Why does one partner’s motivation influence the other partner’s feelings? If a person is having sex for positive reasons, desire and satisfaction will be evident and can carry over to the partner. Conversely, if the reason for sex is negative, the person enjoys it less, and the partner will probably pick up on this fact through body language, perhaps, and respond accordingly.

Does motivation really make a difference in the overall health of a couple’s sexual relationship? There’s good reason to think so. We contacted the married and cohabiting couples four months after they did the original questionnaires and found that the more often individuals reported sex for positive reasons when first surveyed, the more sexual desire they felt at this later time. Individuals reporting sex for negative reasons when first surveyed had lower sexual satisfaction after four months, and their partners reported less sexual satisfaction and less commitment.

It sounds like the conclusion is, if one partner doesn’t want sex, it’s better for him or her to say “no.” That’s not necessarily true. We found, as others have, that couples generally feel closer after having sex for whatever reason. If some nights you’re doing it mostly to avoid upsetting your partner, there’s probably no harm in that and even some benefit. But if this is a chronic pattern, it’s likely to be undermining your relationship.

What can a person who chronically doesn’t want to have sex do to change that feeling? We know from research into other social interactions that motivation can be changed. In the case of sex, feelings generally aren’t 100% positive or negative, but a mix. The first step is to take some time to think about how you feel about having sex with your partner.

Once you’re aware of how you feel, you might try shifting your thoughts toward the positive—what you’ve enjoyed about sex in the past, how this is an opportunity to express love for your partner and how it will bring you closer. It could enhance the experience and even alter your motivation.

Despite this advice, there will inevitably be times when sex isn’t mutually agreeable—due to life circumstances, medical conditions, etc. Honest talk promotes compromise—maybe you can find something that’s pleasurable for you both at the time. You might provide affection, attention and the expression of love in ways other than sex. Perhaps you don’t want to cuddle when you’re not in the mood for sex, fearing it will be interpreted as a gateway to sex, but this gesture could make both of you happy.

Can a certain kind of motivation keep desire alive in long-term relationships? It certainly seems so. In our group of married and cohabiting couples, we asked participants how strongly they were motivated when having sex to please their partners and meet their partners’ needs. We also questioned participants on how much they focused on their own pleasure.

We found that individuals who made their partners’ sexual needs a priority reported stronger feelings of desire. Additionally, this generous approach seemed to prolong desire—four months later, desire was just as strong, while in those who cared less about pleasing their partners, it had declined.

Aren’t there risks involved in putting your partner’s needs before your own? Most people think that giving is good for the self and for relationships. We would all agree that giving a partner a back rub or going to a work function just to make him or her happy is fine. But when it comes to sex, doing something solely to please a partner somehow raises a red flag.

We didn’t look at this in the study, but in general, if one person adopts a partner-pleasing mentality, the other one will, too…and there needs to be some give and take, or the relationship simply won’t last. Just remember to keep your own desires and limits in mind, even as you try to make your partner happy.

What’s the single best piece of advice you can give to help people make their partners happier sexually? Many people find it hard to talk about sex openly, but it’s vital. In fact, a recent study found that partners are particularly likely to be satisfied if they give feedback and communicate what they’re feeling while in bed, rather than before or after.