The protocols and practices of dating, and the terms used to describe it, vary considerably from country to country. The most common idea is two people trying out a relationship and exploring whether they are compatible by going out together in public as a couple. Historically though, in most societies, and during much of human history, marriages were arranged by parents and older relatives with the goal not being love but legacy and "economic stability and political alliances," according to anthropologists. Social rules regarding dating vary considerably according to variables such as country, social class, religion, age, sexual orientation and gender. Behavior patterns are generally unwritten and constantly changing.The average duration of courtship varies considerably throughout the world. Furthermore, there is vast individual variation between couples. It is the result of the productive processing of interior and exterior realities. Bodily and mental qualities and traits constitute a person's inner reality; the circumstances of the social and physical environment embody the external reality. Reality processing is productive because human beings actively grapple with their lives and attempt to cope with the attendant. Two people who are in an intimate relationship with one another are often called a couple, especially if the members of that couple have placed some degree of permanency to their relationship. These couples often provide the emotional security that is necessary for them to accomplish other tasks, particularly forms of labor or work.