The principle of proximity is the tendency for people to form social relationships with individuals who are physically closer to them. Proximity means how close an object or person is physically to you. Someone sitting next to you on a bench is closer in proximity than a person sitting three rows away. The principle of proximity shows that individuals are more likely to form social relationships with people who are closer in proximity to them. You are much more likely to befriend your neighbor or coworker because you are exposed to them more so than a person who lives further away or who works at another place. People who are around each other more are more likely to develop a social relationship.

What is it about a neighbourhood that makes a difference in the lives of youth? One answer is the neighbours. According to Wilson, living in neighbourhoods with many poor families cuts off youth from mainstream society and leads to violence and delinquency. Other research emphasizes the benefits of having neighbours with high socioeconomic status for promoting prosocial outcomes and positive educational attainments. Other demographic features of a neighbourhood thought to be important include racial or ethnic homogeneity or heterogeneity, stability (the frequency with which people move in and out), family or household types (e.g., the prevalence of single-parent families), and density, or population.

Imagine you meet someone for the first time and discover you have a lot in common. You cheer for the same sports team, enjoy watching the same TV shows, and even love the same restaurants. With so much in common, chances are that you'd be attracted to this person. Similarity, or a match of personal aspects with those of another person, is one of the most powerful forces behind attraction and the creation of close relationships. As the old saying goes, and as you have likely experienced for yourself, birds of a feather do flock together.

Concerning the classical question of whether "birds of a feather flock together" or "opposites attract," there is consistent evidence in support of similarity, but very little evidence supporting opposites. However, significant similarity may reduce attraction. To what extent, then, does similarity between lovers enhance or inhibit romance?

I propose that whether a person will conform to or seek distinctiveness from others in a particular consumption situation is contingent on the absence or presence of one's prior positive interaction with the group. I also suggest that this effect will occur in a public context, that is, when an individual's choice is visible to other group members. The results of experiment supported these propositions.

In these two studies, we examined whether the inferences people make about likable and dislikable targets align with the predictions of balance theory. We hypothesized that people exhibit a liking-similarity effect by perceiving greater similarity with a likable person than a dislikable person. To test this hypothesis, we manipulated the likability of a target person and then assessed participants’ perceptions of similarity to that target person. In both studies, people rated likable others as more similar to themselves than dislikable others across a variety of domains (e.g., attitudes, personality characteristics, behaviors). In Study 2, individual differences in self-concept clarity, self-esteem, and preference for consistency moderated the liking-similarity effect.

Reciprocity of liking (also known as reciprocity of attraction and reciprocal liking) describes the tendency for individuals to think positively of others who express positive regard for them. Essentially, we like people who say that they like us. Individuals are more likely to like someone who expresses that they like them. When you learn that someone has expressed liking us we are more likely to have positive feelings for that person. This doesn't work all the time though. Research has shown that people who don't like themselves (have low self esteem) don't like people who like them. Another example in which reciprocity of liking backfires can be with false flattery or 'brown-nosing'. If a person feels as if someone likes them falsely and is expressing it for ulterior motives then they are more likely to dislike that person.

Social exchange theory proposes that social behavior is the result of an exchange process. The purpose of this exchange is to maximize benefits and minimize costs. According to this theory, people weigh the potential benefits and risks of social relationships. When the risks outweigh the rewards, people will terminate or abandon that relationship.

In social psychology and sociology, the idea that social change and stability represent a process of cost-benefit analyses between parties. Social exchange theory is kind of like the mathematical and logical side of a relationship. We add and subtract points for the following: how much effort are we putting into the relationship versus how much effort our companion is contributing, what we feel we deserve in a relationship and how likely is it that we could find a better relationship.

The norm of reciprocity, sometimes referred to as the rule of reciprocity, is a social norm where if someone does something for you, you then feel obligated to return the favor. One area where this norm is commonly employed is in the field of marketing. Marketers utilize a broad range of strategies to convince consumers to make purchases. Some are straightforward such as sales, coupons, and special promotions.