The propinquity effect is the tendency for people to form friendships or romantic relationships with those whom they encounter often, forming a bond between subject and friend. Workplace interactions are frequent and this frequent interaction is often a key indicator as to why close relationships can readily form in this type of environment. In other words, relationships tend to form between those who have a high propinquity. It was first theorized by psychologists Leon Festinger, Stanley Schachter, and Kurt Back in what came to be called the "Westgate studies" conducted at MIT (1950). The typical Euler diagram used to represent the propinquity effect is shown below where U = universe, A = set A, B = set B, and S = similarity: