Social exchange theory states that humans weigh each relationship and interaction with another human on a reward cost scale without realizing it. If the interaction was satisfactory, then that person or relationship is looked upon favorably. When there are positive interactions that produce good reward/cost calculations, the relationship is likely to be more satisfying. But if an interaction was unsatisfactory, then the relationship will be evaluated for its costs compared to its rewards or benefits. People try to predict the outcome of an interaction before it takes place. Coming from a scientific standpoint, Altman and Taylor were able to assign letters as mathematical representations of costs and rewards. They also borrowed the concepts from Thibaut and Kelley's in order to describe the relation of costs and rewards of relationships. Thibaut and Kelley's key concepts of relational outcome, relational satisfaction, and relational stability serve as the foundation of Irwin and Taylor's rewards minus costs, comparison level, and comparison level of alternatives.