Why are reviews always coming back in batches? Send out (say) three papers spread out nicely over a couple of months, and you’ll get the reviews almost at the same time… Well, surely the always bit wouldn’t hold up any empirical test, but it’s striking how randomness plays from time to time (or is it striking that it still feels striking even if we actually know what randomness can look like?).
Railsback & Grimm wrote an excellent introduction to agent-based models. It is quite accessible and can easily be used to teach ABM in the social sciences. I did miss some of the bits that make the current standard choice in the social sciences (Gilbert & Troitzsch) such a good book, like on the nature of modelling in general, or on the advantages of ABM. In this sense, chapter 19 in R&G should come much earlier in the book. Jumping in with an example, as they do, has some advantages, but in my view they’re holding back too much.
Interestingly, at the very end of the book, they seem to undersell ABM. Not that I expect ABM to revolutionize the way social sciences is done, but they don’t mention the advantages for students to learn ABM: While everyone talks mechanism these days, ABM forces students to go beyond mere talk.
Why should we bother with agent-based models? Epstein lists 16 reasons why agent-based models might be worth it; Edmund Chattoe-Brown is a bit more modest with three: combining qualitative and quantitative approaches, transcending linear notions of cause and effect, and building distinctive theories.
Here I want to add another reason: building an agent-based model forces you to think more carefully about the involved mechanisms. Take the following example. A common — usually implicit — model of attitudes towards foreigners assumes that a larger number of foreigners leads to more feelings of threat which lead to more negative attitudes. We can throw this into a regression analysis; it’s all about finding positive correlations. We can ask a few individuals to reflect on the relationship in (in-depth) interviews. But what kind of association should we expect? How much more does more threat actually mean? What is a lot of foreigners? We could go with logical models, as Rein Taagepera suggests, or we could sit down and try to write something in NetLogo — it really forces us to think about what mechanisms are at work, and how we should specify them. Often it also makes us realize how little we know…
Chattoe-Brown, Edmund. 2013. “Why Sociology Should Use Agent Based Modelling.” Sociological Research Online.
Epstein, Joshua M. 2008. “Why Model?” Journal of Artificial Societies and Social Simulation 11(412).
Taagepera, R. 2008. Making Social Sciences More Scientific: The Need for Predictive Models. Oxford: Oxford University Press.
Some things take time; but I have finally made available the full NetLogo code of an agent-based model that simulates different levels of political participation. In the process, I have attempted to use the ODD protocol to describe the simulation. Further description about my implementation of Milbrath’s model of political participation here, here, and here.
The simulation tackles the different levels of political participation to which individuals can be involved in politics: anything between being apathetic and uninterested in politics to holding a political office. It follows Milbrath’s description of the processes and mechanisms as closely as feasible, and results in a realistic dynamic equilibrium. Only one “ladder” of political participation is used, and apparently this works well enough. So yes, I can grow it…
Milbrath, L. 1960. “Predispositions toward Political Contention.” Western Political Quarterly XIII:5–18.
Milbrath, L. 1965. Political Participation: How and Why Do People Get Involved in Politics? Chicago: Rand McNally College Publishing Company.
Milbrath, L., and M. Goel. 1977. Political Participation: How and Why Do People Get Involved in Politics? Boston: Rand McNally College Publishing Company.
Ruedin, Didier. 2007. “Testing Milbrath’s 1965 Framework of Political Participation: Institutions and Social Capital.” Contemporary Issues and Ideas in Social Sciences 3(3).
Ruedin, Didier. 2011. “The Role of Social Capital in the Political Participation of Immigrants: Evidence from Agent-Based Modelling.” SFM Discussion Paper 27.