Commitment isn't just a feeling — it's the outcome of three separate forces, according to one of the most replicated frameworks in relationship science. Here is what psychologist Caryl Rusbult's investment model actually says.
Three Predictors, Not One
Rusbult's investment model (1980) breaks commitment into three independent bases:
- Satisfaction — how rewarding the relationship feels day to day, whether it's giving you what you want out of a partnership.
- Quality of alternatives — how appealing life outside the relationship looks right now, whether that's another person, or simply being single.
- Investment size — what you've put in that would be lost or hard to untangle if it ended: time, shared resources, disclosed history, a merged social circle.
Each contributes on its own. That's the model's central finding: satisfaction alone did not predict who stayed together in Rusbult's original research — alternatives and investment each added independent predictive power on top of it.
Why Split Commitment Into Three Pieces?
A single "how committed are you?" question flattens real differences. Someone with high satisfaction and low investment (a happy, new relationship) can report similar overall commitment to someone with low satisfaction and high investment (a longer relationship running mostly on shared history) — for very different reasons, with very different implications.
Rusbult's 1983 follow-up tracked real couples over time and found all three bases genuinely move month to month. Commitment, in this model, is a dynamic state, not a fixed trait someone simply has or lacks.
Why the Model Has Lasted
A 2003 meta-analysis by Le and Agnew pooled 52 studies and over 11,000 participants and confirmed all three predictors generalize across genders, cultures, and relationship types — one of the reasons the framework is still the reference point in relationship research more than four decades later.
What This Means for Reading Your Own Relationship
The practical takeaway is to resist collapsing commitment into one number. If satisfaction is low but investment is high, that's a different situation than if all three are low, even though both might "feel" similarly uncertain from the inside.
Curious how the three bases actually break down for your own relationship? Take the free Relationship Commitment Test, built on Rusbult's investment model, for a subscale-by-subscale read rather than a single vague number.
Frequently Asked Questions
Who created the investment model of commitment?
Psychologist Caryl Rusbult introduced it in 1980, then tracked couples over time in a 1983 follow-up to show the three predictors move month to month rather than sitting fixed. It has since become one of the most replicated frameworks in relationship science.
What are the three things the model measures?
Satisfaction (how rewarding the relationship feels), quality of alternatives (how appealing life outside it looks), and investment size (what you have put in that would be lost if it ended) — each contributes independently to how committed someone is.
Is commitment the same as love?
No. The model treats commitment as a decision to stay, which can be propped up by investment or a lack of alternatives even when satisfaction is not high. That is different from an emotional experience like love, and it is why the model can explain staying in a relationship that does not feel great.
Can commitment be measured with one question?
Not accurately. Because the three bases can move independently, and even cancel each other out, a single self-report question tends to flatten real differences between very different situations.