Men are more attracted to women who want a fling, while the girls prefer men who are looking for a long-term commitment, according to new scientific research.
And how can these men and women judge whether a person is what they are looking for? By studying their faces, the research found.
A study undertaken by the Universities of Aberdeen, St Andrews and Durham found that the look of your face reveals your attitude towards relationships.
The research was carried out by analysing twentysomethings' responses to pictures of people of the opposite sex.
The 700 young people who took part in the study were shown pairs of pictures of men and women and were told to choose who was more open to short-term relationships and who was likely to be more open to long-term ones.
Participants were also asked to choose who they were more attracted to and who was more masculine or feminine.
Among the males taking part, the women who were judged more open to short flings were also judged the most attractive.
The opposite was true for the women, however, who were generally more attracted to the men they thought were more prone to having a long-term relationship.
Commenting on the study, Dr Lynda Boothroyd from the psychology department at Durham University, told the BBC: "This study shows we can make these kind of instinctive judgements for sex. We have a subconscious - not always right but reasonable - guide."
She added: "Our results suggest that although some people can judge the sexual strategy of others simply from looking at their face, people are not always sure about their judgements possibly because the cues are very subtle.
"Yet preferences for different types of face were actually quite strong. This shows that these initial impressions may be part of how we assess potential mates - or potential rivals - when we first meet them."