Sex File: I fantasise about another guy but never about my husband — is that normal?

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Is it normal to never have sexual fantasies about your partner? I'm still attracted to mine, but when I'm alone, I often find myself thinking about another guy who isn't even as attractive as him. My partner and I are in our 40s and have been together since our 20s. He has asked me to share my fantasies, but I can't tell him about this one.

If you are still attracted to your husband and happily having sex, your best bet is to say nothing. What you fantasise about in your own time is your own business, and there is nothing to be gained by sharing it.

No one really knows why humans have sexual fantasies, but almost everyone does. In fact, sexual fantasy is such a ubiquitous phenomenon that its absence is considered to be a defining criterion for the disorder "inhibited sexual desire". Fantasising about someone other than your husband of 20 years is not unusual either. In one 2010 study, 98% of men and 80% of women reported having fantasies about someone other than their partner in the previous two months.

Although there has been quite a lot of research into sexual fantasy, there is not much agreement on what it means or what it tells us about ourselves. In 2010 the psychoanalyst Brett Kahr surveyed the sexual fantasies of 19,000 British people, and when I interviewed him I asked him why people fantasise about people other than their sexual partners. 

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He explained, as any good psychoanalyst would, that fantasy creates an opportunity for our unconscious minds to privately and honestly examine a relationship. In contrast, the sex therapist David Schnarch takes a more pragmatic view. He argues that fantasy allows couples to experience variety without violating the grounds of monogamy. And finally, the clinical psychologist Marta Meana explains fantasy from a rather more narcissistic perspective. She believes that female sexual fantasy is a reflection of our "desire to be desired". In our fantasies, we are the central pivot. Everyone wants us and all activity gravitates around us.

One thing scientists do agree on is that sexual fantasy promotes sexual arousal. Lots of different studies have shown that more frequent fantasising is associated with more frequent orgasms, as well as greater sexual desire, arousal and satisfaction. In fact, the erotic potential of sexual fantasy is so widely recognised that sex therapists often use it in the treatment of couples with sexual dysfunctions. Although fantasy is largely unconscious, we can harness it to achieve a specific sexual goal, and that might explain why this less attractive man appears to be camping in your head. If, at some point, thinking about someone delivers a powerful orgasm, it can create a kind of Pavlovian response where that person becomes your go-to sexual trigger.

The guilt you feel about your fantasy may only add to its erotic charge. In a relatively old (1985) but nonetheless relevant study, women who experienced a lot of sexual guilt were found to experience a much higher state of arousal after watching an erotic video, whereas women who didn't feel guilty were less aroused. 

Keeping your sexual fantasies private increases their potency, so the best thing you can do is keep shtoom, lean in and enjoy.

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