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Humans have evolved to use intense sexual pleasure, especially orgasm, to control our partners, according to new research.

The research into sexual pleasure and orgasms also examines why women orgasm less consistently than men and asks if orgasms are one of nature's ways of ensuring reproductive success.

Dr Diana Fleischman, a psychologist at the University of Portsmouth, says that orgasm and intense sexual pleasure are such strong forms of positive reinforcement and reward that they can motivate and change our behaviour. Evolution, she says, has trained us into using orgasm and high sexual arousal as currencies. She said:

"All animals engage in behaviour that has positive consequences and learn to associate reward with the stimuli that go with it, eventually finding those stimuli rewarding in their own right. Orgasm and sexual pleasure are intensely fulfilling and when people experience sexual pleasure with another person they start to be rewarded by that person, their form, their smell, their voice etc. Their partner becomes a reward in their own right and ultimately this gives people leverage in relationships.

"Evolution has crafted this desire to reinforce others into making our lives easier through various means, including through sexual pleasure. This means that by withholding the reward, by being curt or delivering the silent treatment will be more painful. When it's in our interest, such as making up after a fight, we are rewarding again."

Positive reinforcement or reward, she says, is much more likely to shape behaviour than punishment. "Think about how we often use tasty, high calorie food as a reward. Food, warmth, sleep and sexual pleasure are all examples of physical rewards that give us pleasure, make us feel good and can cause behavioural changes. Sex is incredibly powerful – when it comes to physical pleasure it doesn't get much better than an orgasm."

Dr Fleischman argues that sexual behaviour is most pleasurable when it fulfils a need. Orgasm can be a signal of devotion to your partner and can improve bonding between parents, and because the human sex drive is not strongly linked to fertility, may have developed to reinforce between two people.

"Rewarding someone with sexual pleasure or orgasm and having someone like you more, could help build a foundation for people in relationships caring for children. Feelings of pleasure and well-being could lead to more positive associations and would make them more likely to forgive one another for errors or indiscretions that would, in the case of a less reinforced pair bond, cause one or both to abandon the relationship.

"A man's pleasure at sexual contact with the mother of his children may prevent him from allocating his effort or resources to other mating opportunities or other children, and for a woman, continued sexual pleasure with the father of her children could prevent her from abandoning a relationship that is provisioning and securing her offspring and could act as a reassuring signal of paternity to her mate."

The research also examines if adaptive behaviour may explain why women experience less consistent orgasms than men, suggesting that there are fewer biological drivers. "For men, sexual behaviour has low potential costs compared with great potential reproductive benefits. However, women can reproduce only once a year and their parental investment is higher as they carry a child for nine months. We should expect evolution to be more selective about the sort of sexual behaviour that should be reinforced with extreme pleasure.

"Yet while women don't need orgasm to conceive, the fact that they do have orgasms is evidence that they serve a purpose. It could be that because orgasm is variable in women that it may be more reinforcing than it is for men.

Dr Fleischman's research, an evolutionary behaviourist perspective on orgasm, is published in the journal Socioaffective Neuroscience and Psychology.