On Monotonic and Nonmonotonic Effects of Arguments in Public Interest Communication

In a previous work we introduced a vector-based extension of value-based argumentation for public interest communication aimed to provide an articulated model of the impact of a communication campaign on a set of target audiences. The proposed model was monotonic, intuitively meaning that adding arguments to a campaign and enlarging the set of the values they cover cannot decrease the effectiveness of the campaign itself. As this property does not always hold in practice, in this paper we extend the model in order to encompass nonmonotonic effects both at the level of quantitative measures of campaign impact and of the acceptability of the campaign arguments with respect to a standard argumentation semantics. In both cases, we identify some sufficient conditions for monotonicity and provide a preliminary discussion about their relevance and applicability in practice.