we might have a whole different life if we'd just happened to live on a different hall in college

[yoss_arian]

http://psych-your-mind.blogspot.co.il/2011/08/my-favorite-unromantic-theories-of-love.

1. The mere exposure effect, discovered by Robert Zajonc (1968), refers to our tendency to like things that are familiar to us - that is, those things and people that we are exposed to most often. The mere exposure effect helps to explain propinquity, the idea that one of the main determinants of interpersonal attraction is physical proximity. In one famous series of studies conducted by Leon Festinger and others (1950), the development of friendships in an apartment complex was directly related to the distance between apartments - people were more likely to become friends with neighbors who lived even just slightly closer, and those who they happened to pass more often on the way down the stairs or to the mailbox. While there may be some degree of randomness and luck in the attachments we form, this doesn't mean that relationships based on proximity are any less genuine and meaningful. But it does suggest that we might have a whole different life if we'd just happened to live on a different hall in college.
2. 
   The commitment equation. How committed are you to your partner? Research suggests that it depends on three main factors: 1) how invested you are in the relationship (i.e., what you've sacrificed/ costs of leaving the relationship), 2) how much you get out of the relationship, and 3) whether there are attractive alternatives. Caryl Rusbult developed the Investment Model by studying college students' relationship trajectories - in statistical analyses, these three variables emerged as the strongest unique predictors of commitment. Here is the equation:
   Commitment = investment + (rewards - costs) - attractive alternatives
   The investment model helps to explain why people might stay in an abusive or unhappy relationship - there may be children involved, financial dependence, or a lack of external social support. It may also explain why people who have too many attractive alternatives available sometimes have trouble settling down.