"Social Behavior is an exchange of goods, material goods, but also non-material ones, such as the symbols of approval or prestige. Persons that give much to others try to get much from them, and persons that get much from others are under pressure to give much to them." (Homans 1958:606). Social behavior as exchange means that a plurality of individuals, each postulated to behave according to the stated behavioral principles, form a system of interaction. Social approval is the basic reward that people can give to one another. In much greater detail, he developed this approach in his book "Social Behavior: Its Elementary Forms" (1961, revised 1974). Homans gives an example of this type of social behavior below: