The Investment Model of Relationship Commitment
Rusbult's Investment Model explains commitment through three independent factors: satisfaction (rewards minus costs relative to comparison level), quality of alternatives (perceived attractiveness of options outside the relationship), and investment size (resources that would be lost if the relationship ended). Together, these factors explain approximately 60-70% of commitment variance across cultures and relationship types.
The model illuminates why people stay in unsatisfying relationships through sunk cost psychology, where accumulated investments create structural barriers to leaving. It also explains domestic violence persistence through deliberate reduction of alternatives, economic dependency creation, and intermittent reinforcement patterns. Big Five traits influence sensitivity to each factor: conscientiousness strengthens investment-based commitment, neuroticism creates unstable alternative evaluations, and extraversion increases alternative awareness.
Healthy commitment is primarily satisfaction-driven, with investment and alternatives playing supporting roles. Practical applications include maintaining reward-cost balance through continuous positive investment, cultivating active choice awareness rather than taking partners for granted, and ensuring relationship investments are joy-producing rather than purely sacrificial.