“In social psychology, propinquity (from Latin propinquitas, nearness) is one of the main factors leading to interpersonal attraction. It refers to the physical or psychological proximity between people. Two people living on the same floor of a building, for example, have a higher propinquity than those living on different floors. Propinquity can mean physical proximity, a kinship between people, or a similarity in nature between things. Propinquity is also one of the factors, set out by Jeremy Bentham, used to measure the amount of (utilitarian) pleasure in a method known as felicific calculus.
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. In other words, relationships tend to be formed between those who have a high propinquity. It was first theorized by psychologists Leon Festinger, Stanley Schachter, Kurt Lewin 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:
The sets are basically any relevant subject matter about a person, persons, or non-persons, depending on the context. Propinquity can be more than just physical distance. Residents of an apartment building living near a stairway, for example, tend to have more friends from other floors than others. The propinquity effect is usually explained by the mere exposure effect, which holds that the more exposure a stimulus gets, the more likeable it becomes.