Proposed explanations for altruistic behavior include biological altruism and reciprocal altruism. The phenotype of altruism relies on recognition of the altruistic behavior by itself. Despite this evidence for empathy-induced altruistic motivation, egoistic explanations may still be possible. Acts which may initially appear to be altruistic CSR may have ulterior motives. Groups with predominantly altruistic members survive better than groups with predominantly selfish members. Manumission was not always charitable or altruistic. "I wish I could believe that his motives were altruistic," wrote Rule. There is debate over whether the alarm calling of prairie dogs is selfish or altruistic. Sympathy can lead to, and be the cause of prosocial and altruistic behaviour. Thus the Cyrenaics believed in the hedonistic value of social obligation and altruistic behavior. Some private donors may seek remuneration although others donate for altruistic reasons. Thus the Cyrenaics believed in the hedonistic value of social obligation and altruistic behaviour. The observed study would then have sadness as less intense than more salient altruistic motivation. Evolutionary game theory has helped to explain the basis of altruistic behaviours in Darwinian evolution. They are useful because they explain the presence or absence of altruistic behavior between individuals.