Investment Model

Determinants of Dependence and Commitment

The Investment Model is based on the principles of interdependence theory, which argues that dependence is a central structural property of relationships—a property that is particularly relevant to understanding persistence. Dependence describes the extent to which a person literally “needs” a given relationship or relies uniquely on the relationship for attaining desired outcomes. How do people become dependent? Interdependence theory identifies two main processes through which dependence grows. First, people become more dependent to the extent that they experience high satisfaction. Satisfaction level describes the degree to which an individual experiences positive versus negative affect as a result of involvement. Satisfaction grows to the extent that a relationship gratifies the individual's most important needs (e.g., companionship, intimacy, sexuality, and belongingness), as well as to the extent that obtained outcomes exceed comparison level or the individual's generalized expectations regarding the quality of a relationship (i.e., expectations based on previous experience or social comparison). Dependence is also influenced by the quality of available alternatives. Quality of alternatives describes the perceived desirability of the best available alternative to a relationship. Quality of alternatives increases to the extent that a person's most important needs could be fulfilled independent of the current relationship (e.g., by a specific alternative partner, the general field of eligible others, or on one's own).

Thus, interdependence theory suggests that dependence is greater when an individual wants to persist in a given relationship (satisfaction is high) and when he or she has no choice but to persist (alternatives are poor). The Investment Model extends these claims in two respects. First, the model suggests that satisfaction and alternatives do not fully explain dependence. If dependence were based merely on the satisfactions derived from a current relationship in comparison to those anticipated elsewhere, few relationships would endure. Many relationships survive periods during which they are not satisfying, even when attractive alternatives are available. The Investment Model therefore asserts that a third factor explains persistence. Investment size describes the magnitude and importance of the resources that become attached to a relationship—resources that would decline in value or be lost if the relationship were to end. People may invest directly or indirectly: Direct investments are those resources that are put directly into a relationship, such as time, self-disclosure, and emotional energy. Indirect investments occur when initially extraneous resources become inextricably connected to the relationship, such as children, mutual friends, or shared possessions. Both types of investments enhance dependence by increasing the costs of ending a relationship—to abandon a relationship is to sacrifice invested resources.

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