Tutorial: Group Stability

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Welcome to the Group Stability Tutorial

Note: in order to run the dynamic simulations referred to in this tutorial, go here, to the Java Applet version. You will be directed to download the latest version of the Java plug-in.

This tutorial is adapted from the paper, "A Theory of Group Stability", by Kathleen Carley, published in The American Sociological Review (1991, Volume 56, June: 331-354). In this paper, Carley outlines a mathematical model of information sharing. This model is used to investigate factors that influence the stability of groups and populations. This tutorial is intended to serve as an aid to the paper and will demonstrate several key results that Carley presents as well as some new findings. Keep in mind throughout the tutorial that the models used are probabilistic and so results will vary with each execution.

Users that wish to further investigate such "Group Stability Societies" can create and observe them themselves using the Group Stability Wizard, which can be run at the end of the tutorial.



  1. The Carley Model of Information Sharing
    1. Connections in the Carley Model
    2. A Simple Example
    3. Information Flow in the Carley Model
  2. Observing a Society
    1. Cultural Homogeneity
    2. Homogeneity Increases with Time
  3. Observations of a Single Group Society
    1. Effect of Agent Preference
    2. Effect of Number of Facts
  4. Observations of a Two-Group Society
    1. What Happens to a Minority in a Society?
    2. Interaction Probabilities Through Time I
    3. Interaction Probabilities Through Time II
    4. Effect of Minority Size on Group Endurance
    5. Some Discussion on the Meaning of Endurance
    6. Minority Culture and Group Endurance
    7. Agent Similarity Preference and Group Endurance
    8. Support from the Real World
  5. Conclusions
  6. Technical Appendix

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