Final answer:
Alex's behavior of donating blood with the hope that others will do the same is an example of reciprocal altruism, a form of prosocial behavior that relies on mutual exchanges for future benefits, rather than selfless actions.
Step-by-step explanation:
Alex's regular donations of blood, hoping others would reciprocate in his time of need, can be best explained by the concept of reciprocal altruism. This form of prosocial behavior is based on the notion that individuals participate in a cooperative act, with the expectation of eventually receiving similar benefits. It differs from pure altruism, which is characterized by selfless helping without expectation of personal gain, and is grounded in empathy towards others. Reciprocal altruism involves a mutual give-and-take and is often found in societies where individuals repeatedly encounter each other, which allows for this cooperative nature to develop and for 'cheaters' to be recognized and penalized.
Kin selection is another factor in altruistic behavior, particularly when the recipient is a close relative, as this could indirectly foster the propagation of shared genes. However, in cases like Alex's, where the individuals benefiting from the blood donation are not likely to be close relatives, reciprocal altruism is a likelier explanation than kin selection.