Persuasion Processes in Populations:
Agent-based Simulation Based on a Social Psychological Theory
Hans-Joachim Mosler
mosler@sozpsy.unizh.ch


     The research to be presented designed an agent-based simulation based upon the social psychological theory of the Elaboration Likelihood Model (ELM). The central statement of this theory is that a person changes his or her attitude in dependency upon the intensity of information processing, that is, dependent upon whether the person is capable of and motivated to think about a topic. If processing intensity, or elaboration likelihood, is high, the effect of the persuasion will depend on the quality of the arguments presented. If processing intensity is low, peripheral cues gain more weight (such as credibility of the information source, length and complexity of the message). In the simulation, agents function according to the rules derived from this theory. They are given varying values of the ELM model variables, and they influence each other mutually.  To validate the simulation, we investigated whether the simulated agents reacted in just the same way that real persons did in experiments that are reported in the literature.
     In order to simulate populations, 10,000 agents were assigned values for the variables in the model on the basis of frequency distributions, with mean value and standard deviation. Moreover, we constructed networks in the populations, whereby the agents belonged to groups that also had contact to other groups. In constructing networks, the number of contact persons an agent has, the size of the group, and the links among groups can all be varied.
     The variously constructed populations can now be investigated with regard to the persuasive effects of different types of information campaigns or action campaigns with multiplicators. Information campaigns function by exerting an influence on a certain percentage of agents in the population through arguments of a certain quality and through peripheral cues. Multiplicators make use of a flexible persuasion strategy, by using arguments or peripheral cues in dependency upon the processing intensity of the agents they must influence.
     The findings of the population experiments reveal that for different populations having different networks, the persuasion strategy must be chosen very carefully, if it is to succeed.