Overview
This lecture introduces threshold models of collective behavior, examining how individuals' decisions depend on the actions of others and applying these models to social phenomena such as riots, innovation, and voting.
Threshold Models of Collective Behavior
- Threshold models analyze situations where actors choose between two alternatives based on the actions of others.
- An individual's "threshold" is the number or proportion of others who must act before they personally take action.
- The model explains that net benefits exceed net costs for an individual only once their threshold is met.
- The overall outcome can be calculated using the distribution of individual thresholds in a group.
Equilibrium and Stability
- The "equilibrium" number reflects the final distribution of choices in the population.
- Stability analysis tests how equilibrium is affected by changes in threshold distributions.
- Small differences in threshold distributions can lead to very different collective outcomes, even in similar groups.
Cautions and Inferences
- Groups with similar average preferences may have very different collective behaviors due to variance in threshold distributions.
- It is unsafe to infer individual motivations from aggregate outcomes or to assume actions are driven by group norms.
Applications
- Threshold models are applicable to riots, diffusion of innovations and rumors, strikes, voting, and migration.
Measurement and Verification
- The lecture addresses challenges in measuring, falsifying, and verifying threshold models in empirical research.
Key Terms & Definitions
- Threshold — The number or proportion of others required to act before an individual will decide to act.
- Equilibrium — The stable state where the distribution of decisions in the group no longer changes.
Action Items / Next Steps
- Review examples of threshold applications in social phenomena.
- Prepare to discuss how changes in threshold distributions could affect group behavior.