Human ethology is the study of human behavior. Ethology as a discipline is generally thought of as a sub-category of biology, though psychological theories have been developed based on ethological ideas (e.g. sociobiology, evolutionary psychology, attachment theory, and theories about human universals such as gender differences, incest avoidance, mourning, hierarchy and pursuit of possession). The bridging between biological sciences and social sciences creates an understanding of human ethology. The International Society for Human Ethology is dedicated to advancing the study and understanding of human ethology.