What concept focuses on equal investment in a relationship from both parties?

The concept that emphasizes equal investment in a relationship from both parties is equity. Equity theory suggests that for a relationship to be healthy and sustainable, both individuals should perceive that their contributions, such as time, effort, and resources, are balanced or fair in relation to what they receive in return. This notion of balance fosters satisfaction and commitment, as each person feels valued and respected for their investment.

In the context of relationships, equity involves both parties striving to maintain fairness, which can lead to better communication and support. When one partner feels they are giving more than the other, it can lead to feelings of resentment and dissatisfaction. Thus, equity is crucial for maintaining harmony and longevity in relationships.