Arguing to motivate decisions

Abstract

Decision makers often have to make difficult trade-offs in situations where multiple aspects matter that are different by nature. For example, in a crisis scenario with a big fire in a factory, trade-offs may have to be made between the safety of the victims and personnel, and the effects on the environment. When making a complex decision, argumentation plays an important role. This thesis addresses the main research question of how a computer can use argumentation to support a person in making a complex decision. To accomplish this, the thesis focuses on answering the following two research questions: (1) how can a computer argue about why a person should prefer one decision to another, and (2) how can a computer effectively support a person in this process. Decision theory literature describes methods to decompose what a person values into general areas of concern, intermediate objectives, and specific evaluation criteria. Although expressive, the quantitative nature complicates their use in supporting complex decisions in a natural way. Argumentation literature describes methods to make decisions. Although arguing is natural, these methods cannot be used to justify preferences between decisions in more complex situations. The thesis proposes a model designed to support evaluating decisions from different perspectives, determining what perspectives should be considered, and how important these perspectives should be. This model combines decision theory with argumentation theory. In my model, value is seen from a perspective and decisions are compared from the perspectives the decision maker cares about. To understand what the decision maker cares about, his perspective is decomposed into perspectives representing the general areas of concern that he has (i.e., the values that he holds). These general areas of concern are further decomposed into intermediate objectives and specific evaluation criteria. In this way, abstract values are made concrete, which enables the computer to compare decisions on these criteria. Given an understanding of the perspectives the decision maker cares about, the computer can then use a number of argumentation schemes to justify why the decision maker should prefer one decision to another. Moreover, several argumentation schemes are proposed to justify why one argument for a decision is stronger than another. In this way, the computer can reason about what the decision maker should do. Dialogues are used to support the decision maker in a natural way. Using a dialogue, the decision maker can put forward a counterargument when he disagrees with an argument of the computer. To accomplish this, an existing dialogue system is extended such that the computer and decision maker can not only exchange arguments, but also argue about the strength of these arguments. While exchanging arguments, the computer learns more about what the decision maker values and can use this information to advance more persuasive arguments. Finally,a method is proposed that use my value model to select the most persuasive argument in the dialogue.