Skip to content

CorentinPernot/interactions

Repository files navigation

🧠 Emergence of Social Hierarchies

How can structured inequalities arise from initially equal societies?
This project explores that question through agent-based simulations inspired by:

  • 🐝 The Bonabeau model (1995) — hierarchy from local competition and memory decay
  • ⚖️ The Sadurní model (2024) — two-group rivalry with normalized prestige

We replicate, analyze, and extend these models with two original contributions:

  1. Unequal importance of winning depending on the group
  2. Internal (intra-group) competition dynamics

🔍 Models at a Glance

  • Bonabeau: agents gain/lose fitness in fights; hierarchy emerges when density is high enough
  • Sadurní: fitness is exchanged between two groups only; total fitness is conserved
  • Our extensions: add asymmetric exchange rules and intra-group competition

📊 Key Results

1. 📈 Phase transition in Bonabeau's model

Hierarchy emerges when density crosses a critical threshold


2. 👑 Determinism (η) controls hierarchy

Low η → no structure; High η → clear dominance

η = 1 (Low determinism)
➡️ No structure, random dynamics
η = 5 (Moderate determinism)
➡️ One dominant leader emerges
η = 10 (High determinism)
➡️ Temporary multi-leadership, then stability

3. ⚖️ Small group sizes increase vulnerability to hierarchy

Minority groups tend to develop stronger inequality (higher Gini coefficients)


4. ⚙️ Asymmetry in victory impact leads to unstable leadership

When the fitness exchanged depends on the winner’s group:

  • If one group loses significantly more in case of defeat, its internal dynamics become unstable.
  • In this group, leaders emerge quickly but are replaced just as fast, producing short-lived hierarchies.
    This models fragile societies, where power is volatile and leadership is constantly shifting.

5. 🔄 Intra-group competition changes how hierarchies form

Adding intra-group interactions introduces new dynamics:

  • When inter-group competition dominates, hierarchy forms through repeated external victories.
  • When intra-group rivalry dominates, strong internal stratification appears early and persists.
    This mechanism alters how hierarchies form, even if the overall inequality remains similar.

About

Interactions

Resources

Stars

Watchers

Forks

Releases

No releases published

Packages

No packages published

Contributors 2

  •  
  •