Emergence in Artificial Societies Evolving Communication and Cooperation in a Sugarscape world by Pieter Buzing

Plan What are ‘artificial societies’? Sugarscape Our goal: communication and cooperation Our model: VUScape Setup Results Conclusions

Artificial Society? Multi agent system –2 levels: autonomous parts, behaviour of whole –AS: more control over agents and world Artificial life –emergent behaviour –AS: important role for individual Agent based simulation –AS: no “problem to solve”, like optimization Social modeling –interactions of agents; effects individual goals on population

Sugarscape Epstein & Axtell, 1996 Torus shaped world: 50 x 50 cells Sugar resources [0 - 4] Agents looking for food Evolution

Sugarscape Agent “Internals” Age [ ] Vision [1 - 6] Sugar Amount [0 - inf] Metabolism [1 - 4] Gender [m/f] Agent Actions Die Move Harvest Metabolise Reproduce

Sugarscape Reproduction rule Agent has gender: male or female Metabolism and vision are genetic! Parents: X Child:,, or Child inherits half of parents’ sugar

Sugarscape Agents will tend to move towards sugarhills Agents with high vision are better off Agents with low metabolism are better off

Our Goal Individual: –limited harvesting capabilities (maxSugarHarvest) –ability to talk and listen Emergent behaviour: –cooperation –communication “If cooperation is needed then talking is beneficial and communication will emerge”

VUScape Had to implement own testbed: VUScape Model is highly based on SugarScape The major changes: –Sugar randomly distributed; multi-agent cells –talkPref [0 - 1] and listenPref [0 - 1] genes –Talk actions and Listen actions –MaxSugarHarvest value: cooperation threshold

VUScape: random landscape Instead of 2 sugar hills a random distribution 2,500 sugar units are spread across 2,500 cells 30% population drop; but still viable world (because it is harder to find food?)

VUScape: limited vision range Vision range set to 1 instead of gene range [1-6] Evolution of vision is not the aim of our project local info from vision, global from communication Short-sighted agents face a tough environment

VUScape: multiple agents Cooperation scheme requires multi-agent cells Higher population size is now possible

VUScape: re-seed sugar Agents find food, wait there until it regenerates We need agents that are constantly searching Explorativeness is increased by reseeding sugar after consumption

VUScape: sex recovery period To avoid possible birth explosions we implement a sex recovery period Recovery period of 5 yields pop decrease of 11% Flattens the age distribution

Step 1: in need of help IF localAmount > maxSugarHarvest THEN inNeedOfHelp

Step 2: talking IF inNeedOfHelp AND rand < talkPref THEN communicate to others on x and y axis: –cell coordinates and sugar value

Step 3: listening IF rand < listenPref THEN listen to others on x and y axis

Step 4: cooperating Use obtained information in movement decision. Two agents can conquer any pile! Cooperation is beneficial for both parties. Communicative agents have an advantage?

Setup Stepwise increase cooperative pressure and monitor the communicative gene values. Experiment A: no communication –Talk and listen genes disabled Experiment B: with communication –Talk and listen genes initiated between 0 and 1 If communication is beneficial then an increase of talk and listen values is expected.

Results: no communication

Results: with communication

Results: listenPref

Results: talkPref

Conclusion Communication makes society more viable High talking and listening preferences give agents a selective advantage Higher cooperative pressure induces communication Future work: other topologies, communication protocols