THE NORM-INFORMATION-DISTANCE MODEL - A STOCHASTIC APPROACH TO PREFERENCE CHANGE IN GROUP-INTERACTION

The Norm-Information-Distance (NID) model is a formalized description of the process of change in collective judgment tasks. The model is de rived in two steps. First, the probability that an individual within a group will change opinion is expressed as a function of relative subg roup size for the new choice, the informational attractiveness of that choice, and the number of alternatives intermediate between the origi nal and the new opinion, which we label distance. Second, these indivi dual transition probabilities are merged into a matrix of group conste llation transition probabilities. The result is a stationary Markov pr ocess that predicts group constellation changes period-for-period duri ng an experimental deliberation. The NID model is tested against data from Stasser and Davis (1981) to successfully show its ability to appr oximate the opinion change process in a two-response case. It is furth er tested against a multiple-response case using 225 male law and econ omics students at the University of Freiburg, Germany, Subjects were i nstructed to determine an appropriate sentence in a mock jury case. Th e NID model was applied to these data in several ways and was able to predict change in choice probabilities at any point during the process . Normative influence as measured by faction size appears to explain m ore of choice change than does informational attractiveness. Informati onal influence seems to work conditionally in the sense that it relate s to only those alternatives that are presently held by at least one g roup member. The NID model has a high degree of flexibility and is exp ected to be useful in a variety of tasks and situations, in addition t o those described in this article.