The professor who believes she's found the secret to sexual attraction in long-term relationships

Telegraph

25-05-2025

Gurit Birnbaum loves sex. So fascinated is she by everything to do with human sexuality that she got a PhD in the subject, from Bar-Ilan University in Israel, nearly 30 years ago. Now she is professor of psychology at Reichman University, and a world-leading expert on sexual behaviour.
'When I was getting my PhD, in my early 20s, I was discovering the joys of sex,' Prof Birnbaum says. 'In the course of my research I found that sex can be a source of joy and excitement for some people, like me, but a source of agony and even boredom for others. I was quite shocked to find that not everyone enjoys sex as much as I do.'
The differences are often most stark inside of long-term relationships, Prof Birnbaum has found. Some couples feel just as attracted to each other decades down the line as they did in the first days of their courtship, and have just as much sex, too, her research has found. For most however, desire declines over time, and frequency of sex with it. Women are especially likely to lose sexual attraction to their partners over the years.
'Humans make sex so complicated,' Prof Birnbaum says, but it's actually pretty straightforward. Sex 'plays an important part in how we form relationships with potential partners, and in holding those relationships together,' she explains. Although 'for some people, sex is not related to how they function within the relationship,' for the majority of us, 'the health of a couple's sex life reflects the health of their relationship as a whole'.
The good news is that our sex lives are not unchangeable, even after years of dissatisfaction. In fact, they can be improved easily, Prof Birnbaum says. Here is what she knows about why desire wanes in long-term relationships, and how to keep enjoying sex well into old age – without having an affair.
We risk breaking up when boredom sets in
Most couples look back fondly on their first months or years together, remembering it as a time when feelings were strong and desire for each other was high.
'When you meet someone new that you want to have sex with, it often feels like a visceral, animal reaction,' she says. Those feelings serve an important evolutionary purpose: 'It's actually a cue that indicates to you at the gut level that this person might be a potential good match for you as a partner, and leads you to find out whether that person might be compatible with you, in that you have similar in hobbies or interests,' Prof Birnbaum explains.
Over time, as we get used to our partners, we don't feel the same desperate need to have sex with them. On the one hand, this allows for a more intimate, stable connection to develop between two people. But at the same time, familiarity makes our partners seem less desirable, a change happens in almost all relationships. The honeymoon phase is a very real phenomenon: on average, those naturally high feelings of desire last for a year to two and a half years, Prof Birnbaum's research reveals, after which maintaining a vibrant sex life is much harder. Yet sex 'preserves connections that are emotionally satisfying,' and a lack thereof 'leaves the ones that don't meet our needs vulnerable to a breakup', says Prof Birnbaum. So finding a remedy can be crucial.
'Novelty is crucial to instigating sexual desire,' says Prof Birnbaum, 'and that doesn't have to mean sex toys and roleplay. Foreplay in this sense starts outside the bedroom.' Going on dates and making time for each other only becomes more crucial as a relationship ages. 'Doing things together means that you keep getting to know your partner and see them in different lights. Talk about new topics with each other, do new and exciting things together, learn new things together, try to observe your partner under different circumstances and in the different roles they take on throughout their lives, that you don't typically see. You will likely discover that your partner isn't this boring person you've already learnt everything about after all, and that there's still more you can learn about them and be excited about.'
It's vital to also have your own life. 'It's important to have friends of your own and hobbies of your own so that you don't feel fully enmeshed. Often this helps to boost desire as it maintains the distinction between you and your partner, meaning that they remain someone you want to chase after.'
Not all desire is the same
At the beginning of a relationship, we typically experience 'spontaneous' desire, Prof Birnbaum says – the sort that 'drives the feeling that you can't get your hands off of each other'. But later on in relationships, 'responsive' desire takes over. 'This means that you have to be committed to the process, accept sexual advances from your partner or initiate sex before you're aroused in the way that you used to be, and really pay attention to what's working to get you or your partner in the mood. In this way, you may feel desire for your partner, get into the mood, and enjoy the sexual interaction, even if you were not
there in the first place.'
Key here is a couple's willingness to foster responsive desire for each other, rather than hoping to bring back the exact same drive from their early relationship. This plays a key part in Prof Birnbaum's 'relationship development model' of sexual desire. 'It's not only a lack of desire itself, but also an apathy to the situation and a reluctance to do the work and meet each others' needs that leads to relationship breakdown,' she explains.
The couples who manage to keep their sex lives thriving for decades are the ones who 'respond to each other's needs, sexually and outside of the bedroom too,' Prof Birnbaum says. 'They're more attuned to what the other needs, and even if one of them doesn't want to have sex, they find a way to navigate the discomfort and find other ways to address the needs that sex can meet – for closeness, intimacy and physical touch.'
Prof Birnbaum recommends that couples start trying to initiate this kind of desire an hour before they'd like to have sex: 'People like to feel courted because it makes them feel wanted.'
Affairs are contagious
If you've ever suspected that infidelity can catch, based on the behaviour of people in your own social groups, then you're right, at least according to Prof Birnbaum. 'Social behaviours can be contagious,' she says. 'It all depends on what's seen as normal within your social groups. If you see one of your friends cheat on their partner, then you're more likely to think that it's acceptable and not that bad, and to behave that way yourself.'
We're all vulnerable to this, says Prof Birnbaum, but some more than others. 'Being intoxicated is one example of what makes someone more likely to cheat, but we are also much less likely to resist temptation if we aren't getting enough emotional resources from within our relationships,' she explains. 'People may cheat on their partners even if they are happy with them, however. It's the balance between the magnitude of temptations, whether you are too depleted to control your urges, and the circumstances that will determine how you will resolve the conflict between desire for others – which we all have – and the wish to maintain your current relationship.'
'When you meet someone new that you're attracted to, there's an internal conflict between maintaining the relationship and coping with the temptation,' she says. 'Personal differences like high levels of narcissistic traits, or feeling insecure, can impact whether cheating happens, as well as how valuable your relationship is to you.'
Building a relationship that's invulnerable to infidelity is very difficult. But often, 'people just don't consider the negative consequences of their actions when they're in the midst of a strong attraction,' says Prof Birnbaum.
'In one of our studies, we asked people to take their partner's perspective when faced with advances from an attractive person, and we found that doing so made them less likely to cooperate with the flirtatious interaction, because their partner and the potential impact on them was on their mind, and they could empathise with the pain that their partner might potentially feel.'
Women and men are different
Women are much more likely than men to lose desire for sex altogether. Hormonal changes around the menopause can influence this, but there's more to it than that, Prof Birnbaum says. 'Women tend to be more attuned to their partner's behaviour, both positive and negative, so the relational context is likely to affect them more strongly when it comes to whether or not they want sex and whether they enjoy it,' she says.
In the worst cases, where a couple are consistently in conflict, this can cause women to 'shut their sexual systems down entirely,' says Prof Birnbaum. 'When a woman's partner behaves destructively and is frequently critical, she will be likely to express that by backing away from her partner sexually, consciously or unconsciously. If her partner doesn't satisfy her emotional needs, or she feels that they aren't invested enough, then they'll just shut their sexual system.'
This is also true when there's a perceived power imbalance, a belief that one person has more power than the other: 'it's a way of asserting yourself and taking back some control,' says Prof Birnbaum, and again it's not always conscious. Then there's the fact that 'many women feel that they get more work in terms of raising the kids and doing chores, on top of working, so naturally they're too exhausted for sex'.
The remedy for this – aside from addressing the root causes – is improving your 'sexual communal strength', as Prof Birnbaum calls it. This is shorthand for 'the motivation you have to meet your partner's sexual needs, while still valuing your own needs, and seeing that this is reciprocated by your partner'. Research suggests that couples who have high sexual communal strength are happier in their relationships overall, regardless of how much sex they have, 'because they engaged in sex for positive, relationship-oriented reasons like fostering intimacy and connection'. This helps to improve the overall relationship 'climate', says Prof Birnbaum.
It's also crucial not to say things to your partner that you can't take back. 'Even in the midst of a heated argument, you have to choose your words carefully and not say things that are going to hurt your partner and stay in their head for months,' Prof Birnbaum says. 'Women especially can find that this makes them very averse to sex.'