propinquity:
The law of propinquity states that the greater the physical (or psychological) proximity between people, the greater the chance that they will form friendships or romantic relationships.
The theory was first crafted by psychologists Leon Festinger, Stanley Schachter, and Kurt Back in what came to be called the Westgate studies conducted at MIT.
In the study, the strongest friendships developed between students who lived next to each other on the same floor, or between students who lived on different floors, if one of those students lived near the stairways.
In non-scientific terms, the Westgate Studies found that the frequency of contact between students was a strong indicator of future friendship formation. [copyblogger]
The word itself simply means close proximity.
Noted in this 9 Chickweed Lane comic.
