Relationship studies are one of the most important aspects of psychology. Indeed, not only do relationships influence people's actions, but they also occupy most of their thoughts, speeches, and concerns (Cardwell & Flanagan, 2003). It is widely recognized that a relationship is defined as a “regular social encounter over a period of time” (Argyle & Henderson, cited in Willerton, 2010). A valid example from Willerton is that when we are not dealing with our own personal relationships, we are always discussing celebrity relationships and looking for depictions of relationships in books and movies. The three main aspects of the study of relationships can be broken down into the formation, maintenance, and breakdown of relationships. This essay will mainly deal with the first two aspects, namely relationship formation and relationship maintenance. Theories regarding the formation and maintenance of relationships will be described for further evaluation, especially when trying to relate them to this era, which may not be similar to the era when these theories were introduced . In relationship formation, the theories discussed will be sociobiological theory and the reinforcement/affect model, also known as reward/need satisfaction theory. In relationship maintenance, theories such as social exchange theory and equity theory will be explored and evaluated in more detail. Sociobiological theory is based on the idea that when women and men are looking for their mate, a characteristic they would seek out because that is who they would have the best reproductive success with, particularly in producing viable offspring which is the basis of evolution (Cox, 2001). The main idea behind this......middle of article......theory offers an evolutionary explanation of relationship formation that focuses on sexual relationships and gene survival. The other theory, which is the reinforcement/affect model, describes why a person would want to form a relationship, limiting the focus to the rewards a person would get from forming that relationship. Economic theories, particularly social exchange theory, predict the possibility of maintaining a relationship through the evaluation of costs and rewards, while equity theory emphasizes the fairness of effort and relationship outcomes (Cox, 2001). However, these theories, like most psychological theories, only take into account the majority and do not take into account individual differences. Further research and improvement on these theories should be conducted as some have been considered obsolete, such as equity theory..