The Basic Concepts of Self-Expansion Theory
Self-expansion theory is a motivational theory advanced by Arthur Aron and Elaine Aron in 1986, which holds that human beings possess a fundamental self-expansion motivation, a drive to enlarge their own capacities, perspectives, resources, and identity. The central insight of the theory is that in intimate relationships people undergo a process of including the other in the self, abbreviated as IOS. A partner's knowledge, experiences, viewpoints, social network, and material resources come to be experienced as though they were one's own. This is not offered as a metaphor. It is a phenomenon that actually occurs at the cognitive level, and the overlapping of the cognitive representations of self and other has been confirmed experimentally. In studies by Aron and colleagues, reaction times shortened when participants processed a partner's characteristics as characteristics of the self.
Self-Expansion and the Revitalization of a Relationship
Self-expansion theory offers a single framework that explains both the powerful attraction of early romance and the sense of staleness that settles over long relationships. Early on, a relationship with a new partner brings rapid self-expansion. The partner's worldview, interests, circle of friends, and knowledge are taken into the self all at once, and the sensation of the self expanding quickly produces intense excitement and happiness. Once the relationship stabilizes, however, the opportunities for new self-expansion available from the partner diminish, and the rate of expansion falls off. This is one source of the staleness couples come to feel. In experimental studies by Aron and colleagues, couples who took on novel and challenging activities together, such as a new sport, travel, or learning something unfamiliar, showed reactivated self-expansion and improved relationship satisfaction. What matters is that the activity be both novel and challenging; activities that are merely pleasant have a weaker effect.
Applying Self-Expansion to Compatibility Assessment
Self-expansion theory has several practical implications for reading where a relationship is headed. First, whether a partner constitutes a source of self-expansion for oneself affects both the initial attraction and long-term relationship satisfaction. A partner who holds knowledge, experiences, and perspectives different from one's own supplies greater opportunity for self-expansion, a point that agrees in part with the complementarity hypothesis. Second, high openness is associated with the strength of the self-expansion motive and predicts a tendency to pursue novel experiences together. Couples in which both partners are high in openness find it natural to share activities that expand the self. Third, agreement on the pace of self-expansion matters. Where one partner seeks rapid growth while the other prefers stability, the mismatch in the desired rate of growth generates friction that has little to do with either person's goodwill. The easy mistake is to read a long list of shared hobbies as a long list of expansion opportunities. Doing together what both partners already do well adds little to either self. What works is entering something unfamiliar to both of them and staying visibly bad at it for a while. The caveat about pace applies here as well: bringing a new challenge to every weekend, to someone for whom once a month is plenty, produces depletion rather than expansion.