Some group memberships are based on sharing a category membership (e.g., women), while others are based on attraction to fellow group members (e.g., groups based on friendships). Based on this distinction, in 1994 Deborah Prentice, Dale Miller, and Jenifer Lightdale identified two primary types of groups to which people may belong. This typology allows researchers to make predictions of how behaviors differ between the two types of groups. Common-identity groups comprise members who share a social category and are attracted to the group as a whole as well as its overarching identity. More specifically, members of common-identity groups are attracted to the group's norms, goals, activities, and other defining features. In contrast, common-bond groups comprise members who are attracted to one another as individuals.