A longitudinal test of the investment model: The development (and deterioration) of satisfaction and commitment in heterosexual involvements.

A longitudinal study of heterosexual dating relationships tested investment model predictions regarding the process by which satisfaction and commitment develop (or deteriorate) over time. Increases over time in rewards led to corresponding increases in satisfaction, whereas variations in costs did not significantly affect satisfaction. Commitment increased because of increases in satisfaction, declines in the quality of available alternatives, and increases in investment size. Greater rewards also promoted increases in commitment to maintain relationships, whereas changes in costs generally had no impact on commitment. For stayers, rewards increased, costs rose slightly, satisfaction grew, alternative quality declined, investment size increased, and commitment grew, whereas for leavers the reverse occurred. Individuals whose partners ended their relationships evidenced entrapment: They showed relatively low increases in satisfaction, but their alternatives declined in quality and they continued to invest heavily in their relationships. Suggestive evidence points to the importance of changes over time in commitment in mediating stay/leave behaviors. The generalizability of these results for men and women and stayers and leavers at all stages of involvement is discussed.