A new study shows that refusing to sleep with a partner on the first date could be one of the keys to making a successful match.
Researchers used a mathematical model to show that more reliable men were willing to wait longer before having sex for the first time.
By contrast, less suitable men were not as likely to continue dating.
Professor Robert Seymour, from University College London (UCL), who created the model, said: "Longer courtship is a way for the female to acquire information about the male. "By delaying mating, the female is able to reduce the chance that she will mate with a bad male.
"A male's willingness to court for a long time is a signal that he is likely to be a good male.
"Long courtship is a price paid for increasing the chance that mating, if it occurs, will be a harmonious match which benefits both sexes. This may help to explain the commonly held belief that a woman is best advised not to sleep with a man on a first date."
Refusing to have sex on the first date increases the chance of finding a good man.