Multiple attitude dynamics in large populations

Abstract

1: Introduction The recent rejection of the European Constitution by the voters in France and the Netherlands (2005) instigated a debate on how this could happen in countries having a basically pro-European-Union attitude amongst the population. We hypothesise that the complexity of the constitution, along with the limited information on its potential effects, caused many people not to process the arguments in defining their vote, but rather used the position of other people, and in particular that of major politicians, to determine their position. Especially the fact that the unpopular leaders of the government strongly campaigned in favour of the constitution may have resulted in a contrasting effect on this topic, despite the population's initial pro-European attitude. Experimenting with the dynamics of attitude or opinion dynamics is not possible using laboratory studies. Field data on the contrary are too complex to identify the causalities of observed dynamical processes. Multi agent simulation provides a tool allowing experimenting with these dynamics, because large series of experiments can be performed systematically varying assumptions on how people change of opinion, and conditions of the initial opinions of the population. This has resulted in an increasing body of research on opinion dynamics using multi-agent simulation. Several researchers have worked on simulating how opinions, attitudes or voting behavior in groups emerges from locally interacting people, some working on binary opinions (e.g., Latane and Nowak 1997, Galam 1999) and some using continuous opinions, where influence is dependant on distance (using a threshold, e.g., Deffuant et al. 2001, Weisbuch et al. 2002, Deffuant et al. 2002, Hegselmann and Krause 2002). These studies mainly used attraction of opinions as a mechanism to generate opinion dynamics, and hence did not use existing behavioural theory on attitude change to formalise agent rules. More recently, researchers have started to use behavioural theory in formalising these rules, e.g. Social Judgement Theory as a formalisation of both assimilation and rejection effects (Jager & Amblard, 2005) and Self Categorisation theory in studying meta contrast effects (Salzarulo, 2004). To study the dynamics involved in attitude change, we formalise relevant social psychological theories in the architecture of agents. The field of persuasion, social influence and attitude change provided us with a rich theoretical perspective on how people change their attitudes, and the factors determining the degree and stability of these changes. In particular the Social Judgment Theory (SJT: Sherif and Hovland 1961) is 2 relevant in understanding how people assimilate or contrast their opinion after being confronted with another position. The basic idea of this theory is that a change of a person's attitude depends on the position of the persuasive message that is being received. If the advocated position is close to the initial position of the receiver, it is assumed that this position falls within the latitude of acceptance of the receiver. As a result, the receiver is likely to shift in the direction of the advocated position (assimilation). If the advocated position is distant to the initial position of the receiver, it is assumed that this position falls within the latitude of rejectance of the receiver. As a result, the receiver is likely to shift away from the advocated position (contrast). If the advocated position falls outside the border of the latitude of acceptance, but is not that distant that it crosses the border of the latitude of rejectance, it will fall within the latitude of non-commitment, and the receiver will not shift its initial position. Formalising this Social Judgement Theory in an agent-based model allowed us to study the conditions under which the attitudes in populations tend to polarize, converge, or display pluriformity (Jager & Amblard, 2005). One main result was that when the latitude of non-commitment gets small, which has been found to happen in crisis situations (O'Keefe 1990), our model produces polarization effects. However, both the experimental based laboratory studies as well as the social simulations addressed processes where only a single attitude is taken into consideration. Yet the example of the vote on the constitution indicates that often more than one attitude is taken into consideration. Many people reported to have voted against this constitution, not because of their negative attitude against this constitution, but because of their negative attitude towards the political leaders advocating a positive vote 1 . In this paper we will study to what extend processes such as congruity affect attitude dynamics in large populations.). In the work that we plan to present in this paper, we will focus on (1) two attitude dimensions rather than one, (2) cognitive effort in the processing of information, and (3) possible effects of mass-media performances of popular versus unpopular leaders. People may spend more or less cognitive effort in elaborating on the attitude position of another person. This is captured in the Elaboration Likelihood Model (ELM; Petty and Cacioppo, 1986), which discerns a central and a peripheral route to attitude change. The central route pertains to the elaboration of pure arguments in a persuasive message and/or new information. Here people are motivated and capable of processing the arguments of the message, whereas peripheral processing is more likely when people's motivation to elaborate is low, and or their cognitive processing ability is limited (i.e., complex issues). The peripheral route is concerned with the elaboration of form aspects or cues of a message such as the number of arguments, the credibility and the attractiveness of the source. The attractiveness of the source is related to similarity of attitudes. Generally, people like to have similar opinions as people they interact with (Festinger, 1954). This implies that when engaging in peripheral processing, people may compare on one attitude dimension how similar they are, and depending on that observed (dis)similarity either accept or reject the information of the other attitude dimension. In the following we will outline the formalisation of this theory in rules that apply to the agents we use. 1 Actually, also a lot of people reported to have voted in favour of the constitution because they disliked the political position of politicians advocating to vote against the constitution.