Agent-based Social Simulation
Bruce Edmonds, Manchester Metropolitan University
Agent-Based Simulation allows the explicit representation and exploration of the complex relationship between individual behaviour and society – the Micro-Macro link. It does it by representing the states and actions of each relevant social actor within a complex computer simulation.
In this technique social actors (people, firms, parts of the environment, etc.) are each represented by separate entities (called ‘agents’) within the simulation. The interaction between the social actors are modelled as messages between the agents. The entities are given behavioural schemata in the form of sets of inter-related rules and each agent has its own individual characteristics (e.g. memory, habits etc.). When the whole simulation is set going all these rules are repeatedly evaluated in parallel, so the effects of each rule will depend upon the past outcomes of rules, resulting in a complex sequence of interactions between the agents.
The technique allows for a precise but relatively rich representation of the complex interaction of social actors over time. The results in terms of the outcomes at both individual and societal levels are then inspectable. The approach provides concrete examples of the results of all this interaction in terms of specific simulation traces. It thus establishes the plausibility of micro-macro explanations and allows the “in vitro” exploration of the possibilities.
This technique can be used in a very detailed and specific manner, enabling the coherent integration of various kinds of evidence (e.g. narrative, time-series, survey, SNA) within a sort-of dynamic computational description. This use contrasts markedly with the reductive modelling of Neo-classical economics, allowing the simultaneous emergence of unpredictable social phenomena and the top-down constraint of individual action from norms and institutions. However their very complexity can make the simulations themselves difficult to understand completely and their level of detail can make validation challenging.
Experts/centres in the UK
- Bruce Edmonds, Ruth Meyer, Centre for Policy Modelling, Manchester Metropolitan University
- Nigel Gilbert, Centre for Research in Social Simulation (CRESS), University of Surrey
- Mark Birkin, School of Geography, University of Leeds
- Nick Gotts and Gary Polhill, Macaulay Land Use Research Institute
Some relevant projects
- The Social Complexity of Immigration and Diversity (SCID) - a 5-year collaboration between the Institute for Social Change (UoM), the Centre for Policy Modelling (MMU) and the Department of Theoretical Physics (UoM)
- The EMIL project - simulating the two-way dynamics of norm innovation, an EU FP6 project. Also available is the EMIL final report
- Freshwater Integrated Resource Management with Agents (FIRMA) - an EU 5FP project applying agent-based simulation and integrated assessment to issues in the management of fresh-water resources. Also available is the FIRMA model final report
- Gilbert, N. and Troitzsch, K. G. (2005) Simulation for the Social Scientist. Open University
- Edmonds, B., Hernandez, C. and Troitzsch, K. G. (eds.) (2007) Social Simulation: Technologies, Advances and New Discoveries, IGI publications.
Resources on the web
- The Journal of Artificial Societies and Social Simulation
- The European Social Simulation Association (ESSA)
- NetLogo (A free, well documented and relatively accessible computer system for individual simulation with a big library of examples)
- Open ABM, a portal for agent based simulation
- The National e-Infrastructure for Social Simulation
- Agent-based modelling course website (includes a complete introductory course on the method)