Aggression between conspecifics in a group typically involves access to resources and breeding opportunities. One of its most common functions is to establish a dominance hierarchy. This occurs in many species by aggressive encounters between contending males when they are first together in a common environment. Usually the more aggressive animals become the more dominant. In test situations, most of the conspecific aggression ceases about 24 hours after the group of animals is brought together. Aggression has been defined from this viewpoint as "behavior which is intended to increase the social dominance of the organism relative to the dominance position of other organisms". Losing confrontations may be called social defeat, and winning or losing is associated with a range of practical and psychological consequences.