The Self-Expansion Model of Motivation and Cognition in Close Relationships

Abstract This chapter surveys the self-expansion model as it relates to romantic, familial, and other close relationships. First, we discuss how the model can be expressed as two related but unique fundamental principles relevant to relationships: (1) there is a basic motivation to expand one's potential efficacy, and (2) one way people seek such expansion is through close relationships in which the other's resources, perspectives, and identities are to some extent "included in the self." Focusing on the motivational principle, we explore its foundations; its relation to other major relationship models; and how self-expansion research has been applied to initial attraction, "falling in love," shared self-expanding activities, partner support for own expansion, infidelity, and dissolution, as well as, briefly, to nonrelationship contexts. In the second half, we focus on the principle of inclusion of other in the self. We explore its foundations; measurement techniques such as the well-known Inclusion of Other in the Self (IOS) Scale, as well as other explicit and implicit approaches; the predictors of inclusion; the effects of inclusion; and, briefly, applications of the inclusion principle beyond personal relationships. Having discussed these two fundamental principles, we consider future directions and the model's broader relation to developmental, evolutionary, and classic philosophical perspectives.