propinquity effect
the tendency of individuals to form close relationships with people they repeatedly encounter. That is, the more often one comes into contact with another person, the more likely it is that one will form a friendship or romantic relationship with that person. For example, next-door neighbors often are friends with one another, as are classmates and coworkers, respectively. The propinquity effect possibly is related to the mere-exposure effect. [first theorized in 1950 by U.S. psychologists Leon Festinger and Stanley Schachter and Austrian-born U.S. sociologist Kurt Wolfgang Back (1920–1999), following a study of students living in the Westgate Apartments at the Massachusetts Institute of Technology]