Creation of edges

Why do people form relationships / edges?

• Psychological explanations
• Strategic explanations
• Exposure explanations

Psychological explanations

We are comfortable with people like us

• Homophily
  • People who are like each other are more likely to become friends

We want our relationships to be in balance

• Balance theory
  • The enemy of my enemy is my friend
  • The friend of my enemy is my enemy

Strategic explanations

We want to be in relationships that help us

• Social exchange theory
  • Do the benefits of relationship outweigh the costs?
  • What resources does each node have and need?
• Social capital
  • People seek to make relationships with powerful others
  • People seek to obtain powerful positions in the network

Exposure explanations

We become friends with our friends’ friends

• Triadic closure / transitivity

Focus of Activity

• Partially a pushback against other explanations
  • People choose or are forced into foci (clubs, neighborhoods, classes, etc.)
  • Ties are often a function of activities, not dyadic choices