TUE 4:00 PM Plenary Accumulation and Control in Systems


Full Report: The Tuesday afternoon plenary session consisted of three presentations. The session provided an in-depth view on current issues of understanding and controlling complex systems. The session took place in Ballroom II and around two hundred people attended. The session chair was Peter Milling from Mannheim University, Germany.


The first presenter was John Sterman from MIT, who presented a paper that he wrote with his colleagues Matthew Cronin and Cleotilde Gonzalez: Why Don’t Well-Educated Adults Understand Accumulation? A Challenge to Researchers, Educators, and Citizens. The authors show that even well-educated and intelligent individuals make systematic errors when it comes to understanding the effects of stock and flow structures, what they call “stock-flow failure”. Sterman and colleagues excluded a wide range of alternative explanations for their findings, such as misinterpretation of graphs, missing context, a lack of motivation, or restrictions of cognitive capacity, to come to the conclusion that "stock-flow failure is a robust phenomenon that appears to be rooted in failure to appreciate the most basic principles of accumulation”. In other words, the stock-flow failure is an inherent characteristic of the human cognitive system. After the presentation, a variety of interesting comments were discussed, for instance, whether having experience in a big number of similar tasks would improve performance, and that in human evolution there was no need to understand accumulation, so that just in the last 50 years people have to deal with complex systems in which the consideration of stock and flow structures becomes crucial.


The second presentation was given by Eva Jensen from the Swedish National Defence College. She reported on work titled Does System Dynamics or Control Theory Help You to Strike a Balance?. Her paper is about an experiment in which participants had to control a simple predator/prey model. Jensen compared two groups of subjects: some with mathematical or system dynamics background and some with a typical social sciences background. Although it seemed that system dynamicists did better understanding the underlying structure and the concept of equilibrium, they did not achieve better playing performance. This result leads to the question of how systemic knowledge can be transferred into controlling skills. In the subsequent discussion, questions like the relationship between IQ and performance, a complexity index for dynamic tasks, or sequence effects in the experiment were considered.


The third paper presented in this session is named Regulatory Impact Assessment for the Transportation Sector – Case Study Germany. The presenter was Grit Walther from Braunschweig Technical University; the paper is co-authored by Grischa Meyer, Thomas Spengler, and Jörg Wansart. In contrast to the other two papers, which are more academic and research orientated from their outset, this study is about an application of system dynamics in a business setting. Nevertheless, it deals from a more practical perspective with the same basic issue of the human ability to understand accumulation processes. Walther and her colleagues study the impact of different legal measures on CO2 reduction and related economic consequences in the automotive industry. They provide a “decision testing cockpit” for policy makers to evaluate different emission reduction policies. After the presentation, questions and answers addressed issues like the role of mass transportation and the appropriateness of industry sponsorship for modeling projects.


Andreas Größler


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