Interdependence theory is a social exchange theory that states that interpersonal relationships are defined through interpersonal interdependence, which is "the process by which interacting people influence one another's experiences"[1](Van Lange & Balliet, 2014, p. 65). The most basic principle of the theory is encapsulated in the equation I = ƒ[A, B, S], which says that all interpersonal interactions (I) are a function (ƒ) of the given situation (S), plus the actions and characteristics of the individuals (A & B) in the interaction.[2][3] The theory's four basic assumptions are 1) The Principle of Structure, 2) The Principle of Transformation, 3) The Principle of Interaction, and 4) The Principle of Adaption.[2][3]