Rusbult’s investment model explains why romantic relationships continue or end by focusing on commitment. Commitment depends on how satisfying the relationship is, how good the alternatives seem, and how much has already been invested.

Core idea

Rusbult argued that the key factor in relationship stability is commitment. A person who is highly committed is more likely to stay in the relationship, protect it, and work through problems. According to the model, commitment is shaped by three main influences:

Path diagram of Rusbult’s traditional investment model showing commitment as the outcome predicted by satisfaction, investment size, and perceived quality of alternatives. It provides a visual summary of the model’s causal logic (three inputs → commitment), which is useful for AO1 description and quick recall. Source

• satisfaction

• comparison with alternatives

• investment

The model is useful because it explains why people do not always leave relationships simply because they are unhappy. A person may remain if the alternatives are poor or if too much has been invested to walk away easily.

The main components

Commitment

Commitment is the intention and desire to maintain a relationship over time. In the model, it is the most direct predictor of whether a relationship will continue.

When commitment is high, people are more likely to:

• think of the relationship as long term

• make sacrifices for their partner

• tolerate occasional difficulties

• try to solve conflicts rather than leave

Commitment is therefore the outcome of the other three factors rather than a completely separate starting point.

Satisfaction

Satisfaction refers to how positively a person evaluates the relationship. A relationship is satisfying when it brings rewards and meets important needs.

Sources of satisfaction may include:

• emotional support

• affection and intimacy

• companionship

• shared goals

• enjoyment and security

Low satisfaction is more likely when the relationship involves repeated conflict, stress, disappointment, or unmet expectations. In Rusbult’s model, greater satisfaction usually leads to stronger commitment.

Comparison with alternatives

Comparison with alternatives means judging whether the available alternatives to the current relationship seem better or worse.

These alternatives do not have to mean another romantic partner. They can include:

• being single

• spending more time with friends or family

• focusing on education or work

• a different lifestyle outside the relationship

If the alternatives seem unattractive, commitment may stay high even if the relationship is not perfect. If the alternatives seem more rewarding than the current relationship, commitment is likely to weaken.

Investment

Investment refers to the resources that a person has already put into a relationship and would lose if it ended.

Investments can include:

• time

• emotional energy

• shared experiences

• mutual friends

• joint possessions

• shared plans for the future

The more someone has invested, the harder it can feel to leave. This means that investment can keep commitment high even when satisfaction drops for a period of time.

How the model explains relationship maintenance

The model suggests that high satisfaction, low-quality alternatives, and high investment combine to produce strong commitment.

Strong commitment then increases the likelihood that the relationship will continue.

This helps explain several common patterns in romantic relationships:

• Some people stay because the relationship is rewarding and enjoyable.

• Some stay mainly because there do not seem to be better alternatives.

• Some stay because leaving would involve losing too much that has already been built up.

The model also shows that these factors can change over time. For example:

• satisfaction may rise or fall as the relationship develops

• alternatives may become more or less appealing

• investment often increases over time as partners share more of their lives

Because of this, commitment is not fixed. It is constantly influenced by changing experiences and circumstances.

Research support

Research has generally supported Rusbult’s model. In studies of romantic couples, satisfaction and investment are usually positively linked with commitment, while attractive alternatives are negatively linked with commitment.

Rusbult’s own research found that people who reported higher satisfaction and greater investment, and who saw fewer appealing alternatives, tended to show stronger commitment. This commitment then helped predict whether the relationship would last.

Later research has also supported the model across different samples of couples. This gives the model good predictive validity, because it can help predict relationship persistence rather than only describe it after the fact.

Evaluation

Strengths

A major strength is that the model explains why people sometimes remain in relationships that are not fully satisfying. This is important because real relationships are not maintained by happiness alone.

Another strength is that the model is clear and testable. The variables of satisfaction, alternatives, investment, and commitment can all be measured, which makes empirical research possible. Support from studies increases confidence in the model.

The model is also practically useful. If commitment falls, it may be because satisfaction has decreased, alternatives have become more attractive, or investment has weakened.

Limitations

One limitation is that the model may describe relationship stability better than it explains the deeper emotional causes of change. It tells us which factors predict commitment, but it is less detailed about why satisfaction or alternatives shift in the first place.

Another issue is that much of the research relies on self-report measures. Participants may not always describe their relationships accurately, especially if they want to present them positively or are unsure of their own motives.

The model can also seem too focused on gradual decision-making. In some cases, relationships end suddenly because of major events, and these endings may not reflect a careful weighing of satisfaction, alternatives, and investment.

Finally, the importance of investment and alternatives may vary across social and cultural contexts. This means the model may not apply in exactly the same way to every couple.