Every Friday on the blog, I answer people’s questions about sex, love, and relationships. This week’s question comes from a female reader whose boyfriend seems to lose sexual interest in women shortly after sleeping with them. The couple is no longer having sex and she wants to know what, if anything, they can do to save their relationship.

My boyfriend and I have been dating a little over 5 months and we have been experiencing problems sexually. Shortly after we started having sex, he was no longer interested in having sex on a regular basis. At first, I was confused and thought it was me but he had explained to me that he's always had this problem. He loses interest immediately after he has had sex with a girl no matter how attractive they are. He gets bored and needs the variety. He's spent the last 10 + years in short term flings and non-committed relationships surfing the web and picking up girls. On an average week, he would sleep with 4-5 different girls. We have now been in a monogamous relationship for 5 months and it has been incredibly hard. We never have sex and I'm starting to feel like we're just best friends. We love each and want to fix this but we don't know how. We just recently went to see a therapist who said he's has never heard of this and didn't know how or if he could help. I'm hoping your expertise and knowledge can point us in the right direction.

Thanks for sharing your experiences and submitting this thoughtful question. Your boyfriend sounds like a walking demonstration of what scientists have termed the “Coolidge Effect,” or the idea that men’s waning sexual interest can be reawakened by variety in partners. This phenomenon got its name from a popular anecdote about a visit that President Coolidge and his wife made to a chicken farm. The story goes something like this:

“Mrs. Coolidge, observing the vigor with which one particularly prominent rooster covered hen after hen, asked the guide to make certain that the President took note of the rooster’s behavior. When President Coolidge got to the hen yard, the rooster was pointed out and his exploits recounted by the guide, who added that Mrs. Coolidge had requested that the President be made aware of the rooster’s prowess. The president reflected for a moment and replied, ‘Tell Mrs. Coolidge that there is more than one hen.’” [1]

The Coolidge Effect has been documented in various animal species, but the classic demonstration came from a study of male rats. This study found that when a male rat was placed inside a cage with several female rats that were “in heat” (i.e., near ovulation), he would mate with all of them until he appeared to be sexually exhausted. However, when a new female was introduced to the cage, the male often experienced an immediately renewed interest in sex and would start mating with the new female [2]. The Coolidge Effect has also been documented to some degree in human men. For instance, in one study, male participants were either exposed to constant or varied sexual stimuli while their level of physical arousal was assessed by a device that records changes in penile circumference [3]. The men who were repeatedly exposed to the same stimuli showed less arousal over time (i.e., they demonstrated habituation); in contrast, exposure to varied stimuli was linked to maintaining higher levels of arousal.

It is important to note that a similar, but somewhat less pronounced pattern also occurs among females. For instance, research on female hamsters has found that after mating with one male hamster until exhaustion, they demonstrate renewed interest in sex when a new male is introduced to the cage [4]. Also, research on human females has found that, just like men, they show some degree of habituation to repeated presentations of the same erotic stimulus [5].

All of this research tells us that losing sexual interest in the same partner over time and being excited by variety is not particularly unusual and may actually be normative. That said, most humans do not appear to lose sexual interest quite as quickly as your boyfriend, although he’s certainly not the only person I have heard of who loses sexual interest almost immediately. Also, I should say that not everyone loses sexual interest in the same person, and some people are capable of maintaining high levels of passion for the same partner for years. Human sexuality is incredibly diverse, and nothing is ever true 100% of the time.

So what can you do to keep your relationship going? One possibility would be to consider having an “open” or nonmonogamous relationship. There are many couples who are able to maintain satisfying relationships while permitting one another to have outside sexual involvements. Of course, I don't know whether nonmonogamy would restore your boyfriend's sexual interest in you, so that may not be the ideal solution. Also, nonmonogamy isn’t the right move for all couples, because different types of relationships work for different people. You and your partner need to decide what’s right for your relationship and figure out how important it is for you to have an active sex life together.

If the two of you want to maintain monogamy, an alternative possibility would be to try incorporating more novelty into both your relationship and sex life, because novelty can breed sexual excitement by facilitating the release of pleasurable brain chemicals. In fact, research has found that the long-term couples who report having the most intense feelings for each other are those who engage in the most new and exciting activities together [6]. In other words, there may be other ways of stimulating that same level of sexual excitement that your partner receives from sexual variety by bringing more novelty into your relationship in other ways. Trying new things and sharing new experiences could potentially reignite the passion you two once felt together.

On another note, you might also want to consider getting a new sex therapist, because I suspect that your boyfriend could potentially have an issue with sexual compulsivity that may need to be addressed. It is not common to see a decade-long pattern of behavior in which a person is constantly searching for partners online and is having at least five new partners per week. It might be worth having him talk to someone about this, especially if he is at all distressed about this behavior or feels that it is out of control.

Last but not least, none of the above should be taken to mean that there is anything wrong with you or that the solution in this case means that you need to do all of the work or that you are the only one who needs to compromise. Your partner needs to accept an equal degree of responsibility and put in just as much effort if you want this relationship to work.

For past Sex Question Friday posts, see here. Want to learn more about The Psychology of Human Sexuality? Click here for a complete list of articles or like the Facebook page to get articles delivered to your newsfeed.

[1] Hatfield, E., & Walster, G. W. (1978). A new look at love. Lanham, MD: University Press of America.

[2] Wilson, J. R., Kuehn, R. E., & Beach, F. A. (1963). Modification in the sexual behavior of male rats produced by changing the stimulus female. Journal of Comparative and Physiological Psychology, 56, 636.

[3] O'Donohue, W. T., & Geer, J. H. (1985). The habituation of sexual arousal. Archives of Sexual Behavior, 14, 233-246.

[4] Lester, G. L., & Gorzalka, B. B. (1988). Effect of novel and familiar mating partners on the duration of sexual receptivity in the female hamster. Behavioral and Neural Biology, 49, 398-405.

[5] Kelley, K., & Musialowski, D. (1986). Repeated exposure to sexually explicit stimuli: Novelty, sex, and sexual attitudes. Archives of Sexual Behavior, 15, 487-498.

[6] O’Leary, K. D., Acevedo, B. P., Aron, A., Huddy, L., & Mashek, D. (2012). Is long-term love more than a rare phenomenon? If so, what are its correlates? Social Psychological and Personality Science, 3, 241-249.

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