New research suggests men treat online giving as a "competitive enterprise," and will donate four times more money to an attractive female fundraiser if another male is also contributing.

The researchers believe this tendency is a subconscious part of human psychology that is a product of evolution, Cell Press reported.

"People are really generous and are right, a lot of the time, to say that their motives for giving to charity are altruistic, not self-serving," said Nichola Raihani of UCL (University College London). "This does not, however, preclude these motives from having evolved to benefit the donor in some way."

The team of researchers looked into the hypothesis that males respond competitively to generosity bids offered by other men in the presence of attractive women. To test this idea, they looked at an online fundraising platform in which people host their own fundraising pages complete with photos and bios. Donations are also posted along with the name of the donor.

"This creates a potential tournament in which donors may compete by responding to how much others have given," said Sarah Smith of the University of Bristol. 

Past research has shown existing donations on a page act as an "anchor" for those looking to donate. This suggests seeing a large or small donation could influence how much a potential donor decides to give. This new study aimed to determine if the gender and attractiveness of the fundraiser would also have an influence.

"We don't think that males are seeing large donations from other males to attractive female fundraisers, and then thinking 'Yeah, I'll give more than him because she will find me more attractive then.' In fact, I think that is quite unlikely," Raihani said. "I think it is more likely that humans have an evolved psychology that motivates us to behave in ways that would have been, on average, adaptive in our evolutionary past--and may still be nowadays also."

The findings also have implications for improving the success of fundraising campaigns; the attractiveness of females was largely based on their facial expressions, and smiling proved to boost their effect on males. It could also be helpful to show large donations early in a campaign.

"Large donations can elicit other large donations, so fundraisers might raise more if they get their most generous friends or family to donate early in the appeal," Raihani concluded.

The findings were published in a recent edition of the journal Current Biology.