Costly Signaling Theory says that although costly, altruistic acts may benefit the altruist indirectly, by establishing a ‘reputation’. By demonstrating the sincerity of one’s good intentions, costly signalling encourages others to engage in reciprocal altruism. Since a costly act shows ability and access to plentiful resources it may also give advantage as regards mate selection
For a behaviour to count as costly signalling, it must be:
- Beneficial to others
- Observable by others
- Costly to the signaller in ways that can’t be reciprocated
- Associated with some strength or fitness of the signaller
CST can be a good framework for explaining how honest communication can be evolutionarily stable despite the pervasive conflicts of interest, since it propose that responding to signals in a way that benefits the signaler is simply the best move the responder can make given the available information. Then , the logic of CST is not base don estándar conditional reciprocity.
In the case of blood donations may signal both health and generosity of the donors; and also, donors might benefit form an enhance reputation, which can lead to greater access to cooperative networks . In this sense, signaling strategies can be viewed as a means of establishing a reputation for ability or willingness to cooperate.
To read more about blood donations as signaling here is the paper “BLOOD DONATIONS AS COSTLY SIGNALS OF DONOR QUALITY”