What’s Wrong with Social Simulations?

Abstract

/. IntroductionIn this paper I will try to answer the question: Why is the epistemic value of so many social simulations questionable? Under 'social simulations' I understand computer simulations of human interaction as they are studied in the social sciences. The reason why I consider the epistemic value of many social simulations as questionable is that many simulation studies cannot give an answer to the most salient question that any scientific study should be ready to answer: How do we know it's true? or, if specifically directed to simulation studies: How do we know that the simulation correctly simulates the phenomenon that it simulates? Answering this question requires some kind of empirical validation of the simulation. The requirement of empirical validation is in line with the widely accepted notion that science is demarcated from nonscience by its empirical testability or fal- sifiability. Many simulation studies, however, do not offer any suggestion about how they could possibly be validated empirically.A frequent reply by simulation scientists is that no simulation of empirical phenomena was intended, but that the simulation only serves a purpose. Then, however, another equally salient question should be answered: Why should we care about the results? It is my strong impression that many social simulation studies cannot answer either this or the first question. In the social sciences it is hard to find useful examples of the use of computers for purely theoretical purposes. In any case, the social sciences are empirical sciences. Therefore, social simulations should contribute either directly or indirectly to our understanding of social phenomena in the empirical world.There exist many different types of simulations but I will restrict myself to agent-based and game theoretical simulations. I do not make a sharp difference between models and simulations. For the purpose of this paper I identify computer simulations just with programmed models. Most of my criticism of the practice of these simulation types can probably be generalized to other types of simulations or models in the social sciences and maybe also to some instances of the simulation practice in the natural sciences, but it would lead us too far afield to discuss these connections here.In order to bring my point home, I rely on the survey by Heath, Hill, and Ciarallo (2009) on agent-based modeling practice for a general overview, and on two example cases that I examine in detail. I start by discussing the survey which reveals that in an important subfield of social simulations, namely, agent-based simulations, empirical validation is commonly lacking. After that I first discuss Thomas Schelling's wellknown neighborhood segregation model. This is a model that I do not consider as being devoid of epistemic value. For, unlike most social simulations, it can be empirically falsified. The discussion of the particular features that make this model scientifically valuable will help us to understand why the simulation models discussed in the following fail to be so. The simulation models that I discuss in the following section are simulations in the tradition of Robert Axelrod's Evolution of Cooperation (Axelrod 1984). Although the modeling tradition initiated by Axelrod has delivered hardly any tenable and empirically applicable results, it still continues to thrive today.Finally, the question remains why scientists continue to produce such an abundance of simulation studies that fail to be empirically applicable. In my opinion the failure to produce useful results has a lot to do with the positivist attitude prevailing in this field of the social sciences. This attitude includes the dogmatic belief in the superiority of the methods of natural sciences like physics in any area of science.2. Simulation Without Validation in Agent-Based ModelsIn this section I give my interpretation of a survey by Heath, Hill, and Ciarallo (2009) on agent-based-simulations. …