Sex in relationships comes before a couple have formed a deep emotional connection, according to new research.
The new findings suggest that sexual desire plays a major role in people's capacity to form an emotional bond with a potential partner.
Psychologists, from the University of Rochester in New York and the IDC Herzliya in Israel, said that this physical intimacy could bring them closer together.
They also say that gender plays no part in trying to form an emotional connection as both men and women try to connect with potential partners when sexually aroused.
Professor Gurit Birnbaum, who led the study at IDC Herzliya, said: 'Sex may set the stage for deepening the emotional connection between strangers.'
Professor Birnbaum and his team found that sexual desire between strangers could encourage people to behave in ways that helped them to bond and connect.
'This holds true for both men and women - sex motivates human beings to connect, regardless of gender,' says Professor Birnbaum.
'Some believe that men are more likely than women to initiate relationships when sexually aroused.
'But when one focuses on more subtle relationship-initiating strategies, such as providing assistance (as proved in the study), this pattern does not hold true.
'Both men and women try to connect with potential partners when sexually aroused.'
Researchers conducted four separate studies and found that sexual desire between strangers could encourage people to behave in ways that help them to bond and connect.
In the first study, participants were introduced to a potential partner of the opposite sex who they met face-to-face.
Men and women lip-synched to pre-recorded music while sitting next to an attractive person of the opposite sex who, unbeknown to participants, was involved in the study.
They rated their desire for them and results showed the greater their attraction, the more they signalled and the more they synched with them.
The second study asked men and women to slow dance with an attractive study insider of the opposite sex and produced the same results.
In a third study, men and women were shown flashes of erotic, non-pornographic images on a screen for 30 miliseconds - which they were not aware of seeing.
They then discussed interpersonal dilemmas with a potential partner, also participating in the study while being videotaped and their behaviour was rated in terms of responsiveness and caring.
Scientists found when the 'sexual system was activated' people showed signs of caring about their potential partner's well-being - which is a way of signalling their interest in a relationship.
The final study included 50 men and 50 women - half of who watched an erotic non-pornography movie scene while the others watched a neutral video about South American rainforests.
They were then matched with an attractive study insider from the opposite sex and told to complete a verbal reasoning task.
The study insiders pretended to get stuck on the third question and ask participants for help and those who had watched the erotic movie scene proved to be more helpful than those who watched the neutral film.
Co-author Professor Harry Reis, of the University of Rochester, said: 'Although sexual urges and emotional attachments are distinct feelings, evolutionary and social processes likely have rendered humans particularly prone to becoming romantically attached to partners to whom they are sexually attracted.'
Professor Birnbaum added: 'Sexual desire may play a causally important role in the development of relationships.
'It's the magnetism that holds partners together long enough for an attachment bond to form.'
Source: The Daily Mail