Orgasms are an evolutionary currency that encourages us to have sex with the people who can meet our sexual and social reproductive needs, psychologists say.
Many things about a partner contribute to their attractiveness, and one of them is the orgasms you (might) have with each other.
The intensity of pleasure that orgasms bring makes them particularly strong evolutionary driver of behaviour towards a partner, psychologist Diana Fleischman of at the University of Portsmouth argues in a paper published in the journal Socioaffective Neuroscience and Psychology.
Orgasms can be thought of a "currency", which influences people to behave in certain ways when courting.
"The idea is that pleasure and bliss states are the currency with which evolution programmes us to do the things it wants us to do," Fleischman told IBTimes UK. "We in turn can use that in turn to influence other people."
Fleischman compares orgasm with a partner to clicker-training a dog. The orgasm gets associated with the partner's body, smell, voice and so on. "When you're in the initial stages of courtship with someone, they learn to associate sexual pleasure with you and then you yourself become rewarding as a stimulus."
Orgasms are not the only currency
However, orgasms are one of many factors that act as drivers of courtship behaviours, Fleischman says. Experiences other than sex and orgasm can lead to positive associations. Even looking at someone you find attractive can act as a reward, she says, citing a paper in which male monkeys would pay to see a picture of a female monkeys' backsides.
"If someone's used to eating delicious meals with you or having interesting experiences with you or getting drunk with you, they can also associate you with certain kinds of reward states. I'm saying that orgasm is a specifically intensely rewarding version of this reward state."
Rare, precious and variable
Orgasms as a currency are more valuable to women than men, Fleischman says. "They're more rare, more precious and more variable."
"Women's orgasms are like a slot machine: you can do the same thing many times but you never know when the reward is going to come," she continues. For men, on the other hand, orgasms are not so hard to come by. For men it's more like pressing a button: "You press it and you get a treat," she says.
The evolutionary basis for this is that for men if there is an ambiguous situation with a partner – you're not sure if they are the best genetic match or not – then it's a good evolutionary strategy to have an orgasm anyway and not worry too much about it.
"For men in an ambiguous condition, this is the best thing to do, because they are more likely to be reproductively successful in that context."
Whereas for women, if the partner is not ideal, it may be better not to have sex, as you risk a big investment of time and energy into having a child that may not be as healthy as if you'd chosen another mate.
"So for women sexual behaviour is not always adaptive, and so the reinforcement should be more selective to the kind of sexual behaviour that's more adaptive," Fleischman says.