A micro-sociological theory, which links self attitudes, or identities, to the role relationships and role-related behavior of individuals.” (Andreassi & Desrochers)
“According to Hogg, Terry, and White (1995), identity theory ‘is principally a microsociological theory that sets out to explain individuals’ role-related behaviors’ (p. 255). It ‘explains social behavior in terms of the reciprocal relations between self and society. It is strongly associated with the symbolic interactionist view that society affects social behavior through its influence on self (Mead, 1934; also see Blumer, 1969), and was developed in part in order to translate the central tenets of symbolic interactionism into an empirically testable set of propositions (Stryker, 1980, 1987; Stryker and Serpe, 1982)'” (p. 256). (Desrochers).

As defined by Andreassi, Desrochers & Thompson in Identity Theory, a Sloan Work and Family Encyclopedia entry. Retrieved  from the Sloan Work and Family Research Network website: As defined by Desrochers citing Hogg, Terry & White: Hogg, M., Terry, D. & White, K. (1995). A tale of two theories: A critical comparison of identity theory with social identity theory. Social Psychology Quarterly, 58, 255-269.