Communicating the cost of your altruism makes you cool—competitive altruism and sexual selection in a real-life charity situation

Maintaining a good reputation is crucial for humans. Altruism, e.g. charity, may serve as a costly signal that enhances reputation based on the real or communicated cost. Fundraising via charity running triggers competitive altruism when potential donors donate in reaction to the reputation increase of the fundraiser. Using real-life data of marathonists and half-marathonists (388 runners) and their 9281 donors, the present research focuses on how the communicated cost and goal of a charity run affected the potential donors. We analysed the introductory texts of the runners presented online according to the cost and the social benefit of the fundraising communicated by them. We have shown that emphasizing more the subjective cost of running and the social benefit of the goal, or writing a longer text, attracted more donors and, even though the average amount of donation per donor did not increase, still lead to a greater amount of donations collected overall by the fundraiser. It was also shown that a higher communicated subjective cost resulted in a higher ratio of opposite-sex donors, both in the case of male and female runners, suggesting that the communication of the cost of an altruistic act might be the object of sexual selection. Significance statement A good reputation is crucial for humans, as a reputable person enjoys several benefits. One way to maintain a good reputation is to be altruistic, e.g. doing charity. A seemingly high cost and a socially accepted goal may result in a higher reputation. Using data from a charity running community we demonstrate that fundraisers who emphasize their subjective cost (how difficult to run), and emphasize the good goal of the charity, attract more donors, and even though the average amount of each donation does not increase, a higher number of donors results in a greater amount of donations collected overall. Talking about the difficulties of the charity run results in a higher ratio of opposite-sex donors. Our results may be helpful to plan more successful charity events or to make a human community more altruistic and cooperative in general.