Opinion Dynamics and Collective Decisions: Procedures, Behavior, and Systems Dynamics

• Applicant: Privatdozent Dr. Jan Lorenz
• Subject Area: Political Science
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265108307

Of democracy we expect that it enables us to utilize collective intelligence such that our collective decisions build and enhance social welfare, and such that we accept their distributive and normative consequences. Collective decisions shall aggregate our individual preferences and judgments, but the trilemma of democracy is that any procedure, which aggregates non-dichotomous choices, must violate at least one democratic principle: respect of majority, openness to pluralism, or collective rationality. From a positivist perspective instead, individuals dynamically form and change their preferences and judgments through discussion and deliberation. The trilemma would be solved if these opinion dynamics lead to consensus, but sometimes it that opinion dynamics produces the opposite: persistent polarized opinion landscapes. Most collective decisions and many political discussions focus on discrete choices as for people or proposals. This is surprising as the underlying individual judgments and preferences at stake are typically of a gradual nature. Many decisions have choice sets which are naturally continuous as the budget plans, the minimal income, a tax rates, or the assessment of a price, probability, or risk. In contrast to most political models, the project focusses on decision procedures where participants can make choices from a continuum. Decision procedures and deliberation in a continuum of opinion create opportunities for compromising and gradual adjustments. They will be formalized as a rational-choice model of continuous opinion dynamics and collective decision, where participants have individual, epistemic and social preferences. Based on the model, group decision experiments shall help to understand humans' and groups' behavior in such games of simultaneous bargaining, truth-finding, and coordination. This shall deliver arguments how to best solve the democratic trilemma in a specific situation. Evidence shall be found when it is good to foster and when to avoid deliberation.In large groups, opinion dynamics naturally goes beyond the scope of the individual and consequently phenomena as consensus, bipolarization, fragmentation or extremism might also be the result of self-driven macroscopic systems dynamics. Such macroscopic phenomena are quantified in the project by analysis of opinion landscapes extracted from social surveys and rating data from the Internet. Their evolution is explored by agent-based simulation models which are systematically analyzed by methods of the physics of complex socio-economic systems. This delivers an understanding of the hidden driving forces of opinion dynamics and how they prevent or foster convergence to consensus.Alongside the project, policy recommendations shall be derived for possible procedures of deliberation and the aggregation of decisions about predictions, taxation and budgeting.

• DFG Programme: Research Grants