Differences in sexual desire can be highly problematic. Romantic relationships are distinguished from all others in that they are fundamentally sexual in nature. Furthermore, the vast majority of people expect their intimate relationship to be sexually exclusive. And yet, people differ widely in terms of how much sex they want, so it’s not surprising that one of the most common reasons that couples seek counseling is discrepancies in sexual desire.
Past research has shown that, in long-term relationships, one of the partners will consistently want more sex than the other partner, and that this can create considerable tension and frustration for both. Previous studies have also shown that partners who significantly differ in their level of sexual desire report lower levels of both relationship and sexual satisfaction compared with those whose libidos are more evenly matched. This is known as the mismatch effect .
More generally speaking, research shows that couples are happier when they’re similar to each other over a wide spectrum of values, including personality traits and personal preferences as well as political and religious beliefs. So, it only seems reasonable that couples should be happier if their levels of sexual desire are closely matched. However, the observation that some couples still report high levels of relationship and sexual satisfaction despite differences in libido led University of Toronto psychologist James Kim and colleagues to question the validity of the mismatch effect.
Measuring the Mismatch Effect of Differences in Sexual Desire
Sexual desire mismatch is typically measured by calculating what are known as difference scores. For example, a husband and wife each indicate their level of sexual desire on a scale from 0 to 5 in response to the question, “How often do you want to have sex?” In this case, 0 would mean “less than once a month” and 5 would mean “every day.” If Andrew wants sex twice a week (4) and Bianca wants it once a week (3), then their difference score is 1 — that is, 4 minus 3.
Prior research shows that couples with wide gaps in sexual desire (“twice a week” versus “once a month”) report lower sexual and relationship satisfaction than those with narrower gaps (“twice a week” versus “once a week”). However, Kim and colleagues argue, this emphasis on absolute differences ignores an important finding in relationship science — specifically, the observation that couples that have sex frequently are more satisfied with their relationship and their sex life compared to those who have sex less often.
Kim and colleagues asked whether the so-called mismatch effect was due to absolute differences in sexual desire, or if it was really just a matter of how often they had sex. Consider a second couple, Caleb and Danielle. Caleb indicates that he wants sex twice a month (2), while Danielle wants it once a month (1). Their difference score is 1 (2 minus 1), the same as Andrew and Bianca’s above.
These two couples both have the same degree of difference in sexual desire. However, their frequency of sexual activity is quite different, with Andrew and Bianca doing it once or twice a week, while Caleb and Danielle do it only once or twice a month.
According to the mismatch effect, we would expect both couples to report similar levels of sexual and relationship satisfaction. Based on sexual frequency, however, we would expect Andrew and Bianca to be happier with their sex life and relationship than Caleb and Danielle. Kim and colleagues pitted these two competing hypotheses against each other in a study of 366 mixed-sex couples.
Differences in Desire or Frequency of Sex?
For this study, each member of the couple indicated their level of sexual desire. The researchers then calculated a difference score for each couple, as is typically done in studies of the mismatch effect. The participants also reported their sexual and relationship satisfaction.
After they had collected their data, the researchers looked at both differences in sexual desire and frequency of sexual activity to see which better predicted sexual and relationship satisfaction. The results challenge the received wisdom on this topic.
First, Kim and colleagues found that couples that are matched in sexual desire are not necessarily more satisfied, sexually or relationally, than those who are mismatched. This result seems to directly refute previous findings of a mismatch effect. Instead, the data from this study showed that couples are more satisfied when both partners exhibit high levels of sexual desire, even if they're mismatched.
Thus, in the examples above, we would expect Andrew and Bianca to report higher levels of sexual and relationship satisfaction than Caleb and Danielle. Even though both couples have the same degree of sexual desire mismatch, the first couple has sex more frequently than the second couple.
Dealing with Discrepancies in Sexual Desire
This finding has important implications for couples counseling. When couples seek help for differences in sexual desire, counselors often encourage them to find a compromise frequency somewhere between the two. However, the results of this study suggest it may be better to help couples overcome low libido rather than settle for an unsatisfying compromise.
Although low sexual desire can have many causes, it’s frequently due to tensions within a relationship. If Caleb and Danielle can resolve the issues dampening their libidos, they’ll likely be happier in their relationship, and may want to have sex more often as well.
And why are Andrew and Bianca so happy with their relationship despite their mismatch in sexual desire? Andrew may not be getting as much sex as he’d like, but he’s getting enough. Likewise, Bianca is willing to have sex with Andrew even when she’s not in the mood, simply because she enjoys making him happy.
A 2016 study by psychologist Amy Muise and colleagues found that relationship satisfaction increases with sexual frequency up to once a week, but not more than that. This suggests that when couples have sex frequently, around once a week or so, differences in sexual desire are likely to be less important.
Rather, it's when couples have sex less than once a week that sexual desire discrepancy becomes an issue, especially for the partner with higher libido. Thus, it’s more important for low-frequency couples to examine the issues dampening their sexual desire rather than focusing on the differences between them.
[With minor changes this article is reprinted from the May 12, 2021 edition of Psychology Today.]