A new scientific review into the apparently inevitable decline of sexual desire, and arousal, in response to 'partner familiarity', has just been published from the University of British Columbia.
Academics Heather Morton and Dr Boris Gorzalka examined the impact of a new partner on sexual arousal and desire, and whether there is a difference between men and women in this respect.
The review reports a recent British survey which found women recorded an average of eight opposite sex sexual partners over their lifetime, while men reported 12. But the survey also found 22% of women and 14% of men reported having only one sexual partner in their lifetime.
Heather Morton and Dr Boris Gorzalka report that when asked about fantasising about someone other than their current sexual partner in the past two months, 98% of men and 80% of women reported having had such a fantasy.
Research like this suggests that a large proportion of men and women may experience a desire to engage in sexual activity with novel partners; however, this appears to be more common in men.
The new analysis of this research is entitled, Role of Partner Novelty in Sexual Functioning: A Review, and was inspired partly by the finding that preference by males towards novel females has also been found in nonhuman primates, such as chimpanzees and rhesus monkeys, and indeed across the animal kingdom. Male fruit flies preferentially court novel females over familiar females.
Heather Morton and Dr Boris Gorzalka report evidence from laboratory studies where an erotic film is shown repetitively, it is then followed by a different erotic clip, while physiological and subjective sexual arousal are measured throughout.
Generally speaking men's sexual arousal declines when shown the same erotic stimuli over and over again, but is rekindled when new erotic stimuli is introduced. Whether the same consistent results are found for women by similar experiments is a more mixed picture, and there have been fewer studies .
For example, men were found in one study to have a greater increase in sexual arousal in response to different actors engaging in the same erotic activity, whereas women had a greater increase in sexual arousal to the same actors engaging in different activities.
This new overview of all this research is published in the Journal of Sex & Marital Therapy, and contends that evolutionary theory predicts genetic success is based upon producing the maximum number of descendants.
Yet in most modern societies, the authors argue, men and women are no longer aiming to produce the maximum number of offspring possible. However, modern humans have inherited the genes and biological predispositions that led to our ancestors fulfilling this goal of evolution.
Arousal and desire would have evolved to promote the most successful mating strategy. So if having a novel sexual partner produced the greatest number of offspring who survive to procreate, then sexual desire and arousal should be greatest in these situations.
'The good genes hypothesis' proposes that men could be categorised in terms of mating strategies. 'Cads' specialise in short-term mating, these men have high genetic quality which they promote to women by being highly competitive, dominant, and brave. 'Dads' in contrast adopt a long-term mating strategy, where they compensate for their genetic quality with their potential to invest in their offspring by showing compassion, kindness, and industriousness.
The 'good genes' theory contends it is most beneficial for women to engage in long-term relationships with 'dads' in order to provide the most care for their offspring; however, if the opportunity presents itself, short-term affairs with 'cads' may provide them with offspring of better genetic quality.
Studies find that when women are given descriptions of a man who is competitive, dominant, and brave (cads), and one who is compassionate, romantic, and industrious (dads); they are more likely to select the latter for long-term relationships and the former for short-term relationships.
Heather Morton and Dr Boris Gorzalka contend that extramarital affairs are perhaps another strand of evidence for there being a 'natural' desire for novel partners.
They report that various studies find that between 23% and 29% men and 12% and 23% women, have had sex outside of a supposedly monogamous relationship. If affairs are driven by a desire for partner novelty, then familiarity with one's current partner increases the risk of infidelity, and indeed one study found that that each month in a relationship increased the risk of an affair by 2%.
If novelty does increase sexual desire and arousal, then those engaging in affairs should find sexual activity to be more frequent and pleasurable with their new partner, argue Heather Morton and Dr Boris Gorzalka. One study they quote found that 86% of respondents reported that their extramarital sexual relations were 'somewhat' or 'very' satisfying.
Yet if research also finds that only 38% of females and 25% of men reported quality of sex during the marriage as low, is there hope that long term couples can rescue their sex life? The right strategy will probably arise from an understanding of why 'familiarity breeds contempt'.
Heather Morton and Boris Gorzalka report other research finds that married women identified overfamiliarity as a primary contributing factor to declines in sexual desire, in fact some women felt certain that their desire would return in response to a new partner. This finding is further supported by another study which found that women who reported an absence of sexual yearning towards their partners, continued to experience strong sexual desire towards other men.
Studies also find that men in long-term relationships reveal that they view sexual boredom as an inevitable feature of all sexually exclusive relationships, rationalizing it as the price one must pay for long-term companionship. When asked what they believed were the underlying causes of their sexual boredom, men's most frequent responses involved over-familiarity, whereas women most regularly suggested complacency.
However in a study of 346 college students, less than 1% denied wanting to settle down with one mutually exclusive sexual partner, and when asked to select their ideal mating arrangement, both men and women overwhelmingly preferred strict monogamy to risk free casual extramarital sex.
Heather Morton and Dr Boris Gorzalka conclude that the vast majority of people do appear ultimately to want long-term relationships.
The conundrum appears to be that while this arrangement produces many practical benefits, it almost certainly will not (according to evolutionary theory) deliver maximal levels of sexual arousal and desire.
Our experience as therapists working with sexual and relationship problems is that extra-marital affairs for women are as if the women fall in love with themselves again. They feel that they are sexually noticed. This erotic attention is lacking from their marriage partners who eventually primarily see their female partners as mothers to their children. This identity is something to which these women also very much subscribe themselves.
Maybe if we and our partners could learn to see ourselves differently within our long term relationships, this could help rekindle desire?