Parochial altruism is a concept in social psychology, evolutionary biology, and anthropology that describes altruism towards an in-group, often accompanied by hostility towards an out-group.[1] It is a combination of altruism, defined as behavior done for the benefit of others without direct effect on the self, and parochialism, which refers to having a limited viewpoint. Together, these concepts create parochial altruism, or altruism which is limited in scope to one's in-group. Parochial altruism is closely related to the concepts of in-group favoritism and out-group discrimination.[2] Research has suggested that parochial altruism may have evolved in humans to promote high levels of in-group cooperation, which is advantageous for group survival.[3][4] Parochial altruism is often evoked to explain social behaviors within and between groups, such as why people are cooperative within their social groups and why they may be aggressive towards other social groups.