Dr Peter Sozou and Professor Robert Seymour from University College London (UCL) have developed a mathematical model that shows how expensive but worthless gifts may help facilitate courtship.
Reporting in the journal Proceedings of the Royal Society of London B they analysed the function of a courtship gift and what the characteristics of a 'good' gift are.
They show that gifts can act as a signal of a man's intention. Offering an expensive gift may signal a long-term commitment but the man must be wary of being exploited by a gold-digger who intends to dump him once she gets the gift.
By modelling courtship as a sequential game, they show that an extravagant gift, which is costly to the man but worthless to the woman, may solve the problem.
A costly gift signals the man has long-term intentions but by being worthless to the woman, gold-diggers are deterred.
The researchers also show that a modified form of the model may apply to species where males do not help to raise the young.
Dr Peter Sozou, of UCL's Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, says:
"Gift-giving by males is a feature of human courtship and mating systems in a number of species. Females invest more resources than males in offspring and so must take care to pick the best partner possible, something that's not always easy to gauge from general cues such as appearance.
"In humans, a girl wants a guy who is attractive to her and will help raise their children. The worst pay-off, reproductively, is if she hooks up with an unattractive male who, literary, leaves her holding the baby.
"Guys are less likely to offer expensive gifts to females they don't have a long-term interest in. And girls won't be impressed by cheap gifts. By offering expensive but worthless gif
Contact: Judith H Moore
University College London