To understand the origins of this seemingly irrational behaviour, we need to consider how human altruism emerged in the first place.

According to evolutionary psychology, hardwired human behaviours should have evolved to improve our survival and our ability to pass on our genes to another generation. In the case of altruism, generous acts could help us to foster good relationships within the group which, over time, help to build social capital and status. 

Reputation is “positional” – if one person rises, the others fall. This can create a strong sense of competition, which means that we’re always alert to the possibility that other people are getting ahead of us, even if they are achieving their status through altruism. We’ll be especially resentful if we think that the other person was only looking for those reputational benefits, rather than acting out of a genuine interest in others, since it may suggest a cunning and manipulative personality more generally.

Altruistic behaviour can make us walk a metaphorical tightrope. We need to balance our generosity perfectly, so that we are seen as cooperative and good, without arousing the suspicion that we are acting solely for the status.

If there’s no good evidence to suggest that their acts of generosity are self-serving, we may choose to give them the benefit of the doubt, knowing that our uncharitable intuitions may be fuelled by our own fears of losing status. 

Ultimately, the only fool-proof way to avoid do-gooder derogation may be to do your best deeds in complete secret. And if others happen to discover the truth, despite your attempts to hide it – well, the good reputation that follows is simply a bonus.