Rusbult's Investment Model

Rusbult et al (2011) suggested that commitment is an important factor in relationships, referring to the intention or desire to continue the relationship (believing it to have a future).

Commitment is affected by these factors:
- Satisfaction and comparison with alternatives.
- Investment size.
- Satisfaction vs. Commitment.
- Relationship maintenance mechanisms.

This is similar to the ideas of social exchange theory.

In relationships, each partner considers the rewards and costs (comparison level = CL), and satisfaction will be high if there is seen to be profit from the relationship. 

If a partner does not consider that they will get more profit elsewhere, the relationship is more likely to continue.

However, satisfaction by itself will not be enough to determine the continuation of a relationship.

Investment refers to the extent and importance of the resources associated with the relationship.

If the relationship ends, this investment is lost.

There are two types: intrinsic investments and extrinsic investments.

• Intrinsic Investments are resources such as money and possessions which are put into a relationship by the individual partners. They also include things like energy, emotion, and self-disclosures.
• Extrinsic Investments are factors brought by the relationship, such as a house, car, mutual friends, and children. They also include shared memories.

If the size of investment increases, along with the sense of satisfaction being seen as acceptable, each partner's commitment to the relationship will be stronger.

According to the theory, commitment is more important than satisfaction.

This can explain why people who are dissatisfied still continue with a relationship.

It is because they do not want the investments they have put in to go to waste, so they will work hard to try to increase satisfaction and repair the relationship.

Each partner puts in work to promote and maintain a relationship, and will put their partner's interest first, forgiving any serious transgressions from the partner.

Cognitive strategies are also used to maintain a relationship, for example, thinking in an unrealistically positive way about the partner, and being negative about other people's relationships (so making a negative comparison with alternatives).

+ Le and Agnew (2003) found that in 52 studies with 11,000 participants, satisfaction, comparison with alternatives, and investment size all predicted relationship commitment. Where commitment was greatest, relationships were longer-lasting. This was true across different cultures and in homosexual, as well as heterosexual, relationships, strongly supporting the theory.

+ The theory can be used to explain why people stay in abusive relationships, where the abused partner clearly cannot be satisfied. There is evidence suggesting female victims of domestic abuse who stayed with their partner were more likely to report having invested a great deal in the relationship, supporting the prediction of the theory.

- Investment may have been oversimplified in the theory. This is because, in the early stages of a relationship, little investment is made by either partner, but this does not mean the relationship does not last. Therefore, investment may need to be extended to include factors such as future planning. This measn that original explanation may be incomplete.