Truls Pedersen

Agents Homogeneous: A Procedurally Anonymous Semantics Characterizing the Homogeneous Fragment of ATL

In many multi-agent scenarios we encounter homogeneous groups of agents; agents that have the same actions available, and for which the system does not care who performs a given action, but only cares about how many agents perform it. Sometimes homogeneity is a descriptive fact, arising from a lack of interest in agents’ identity, or the fact that we are simply unable to distinguish between them. Other times, it is a normative requirement, for instance in the context of voting, where we do not want the outcome to depend on who voted for what, only on how many votes each candidate receives. Another important notion is anonymity, which also often arise in multi-agent scenarios, either because we do not know an agent’s identity, or else because the systems comes with an explicit commitment to ensure that this information is kept secret. Clearly, the two notions are closely related, and in this paper we explore the relationship that exists between them within the framework of Alternating-time Temporal Logic. We add an homogeneity axiom to this logic, and proceed to show that the resulting logic, which we dub hatl, is sound and complete with respect to a class of structures that are both homogeneous and procedurally anonymous, meaning that no information whatsoever needs to be maintained about the actions of individual agents.

Reasoning about reasons behind preferences using modal logic

Preferences play a crucial role in the theory of rationality, and therefore also to computational social choice and artificial intelligence. In formal models it is usually assumed that preferences are primitive objects, and little concern is devoted to the question of how they are formed or where they come from. Recent work in rational choice theory challenges this assumption, however, and aims to give more internal structure to the notion of a preference. The focus so far has been on modeling faculties of individual agents, such as their mood, mindset, and motivating reasons. In this paper we contribute to this development by developing a modal logic for reasoning about preferences that depend on a set of motivationally salient properties. The main result is a translation showing how reasoning in this logic can be captured by reasoning in a standard modal logic (KT with universal modality). It follows that reasoning systems and algorithms developed for modal logic (with universal modality) can be employed for reasoning about reason-based preferences. We then discuss how the approach can be generalised to the multi-agent case, and allows us to reason about agents who disagree because they are motivated by different factors, and who might be able to reach consensus simply by changing their perspective.

Concurrent Game Structures with Roles

In the following paper we present a new semantics for the well-known strategic logic ATL. It is based on adding roles to concurrent game structures, that is at every state, each agent belongs to exactly one role, and the role specifies what actions are available to him at that state. We show advantages of the new semantics, provide motivating examples based on sensor networks, and analyze model checking complexity.

Reasonably rational: reasoning about reasons behind preferences using modal logic

Reasoning about preferences is a fundamental component of rationality, and therefore central in AI and computational social choice. Most logic-based frameworks for representing and reasoning about preferences assume that preferences are arbitrarily given, typically as a ranking of a set of alternatives or using utilities, with little concern about how preferences are formed or where they come from. Recent work in rational choice theory, however, has devoted attention to giving more internal structure to the notion of rationality, focusing more on the faculties of individual agents, such as their mood, mindset, and motivating reasons. In this paper we develop a modal logic for reasoning about preferences that depend on a set of motivationally salient properties, based on recent work on reasons behind preferences by Dietrich and List. The main result is that we show how the problem of reasoning in this logic can be translated to reasoning in a standard modal logic (KT with universal modality), and consequently that reasoning systems and algorithms developed for modal logic (with universal modality) can be employed for reasoning about reason-based preferences.

Female Voices in the News: Structural Conditions of Gender Representations in Norwegian Newspapers:

The article presents a hybrid analysis combining manual content analysis of 9,131 sources in 5,544 news stories across 75 publications, with computational gender recognition producing 551,102 names from 320,228 articles across 125 newspapers. The article investigates the significance of structural features for the presence of women in the news. Results show female sources are only equal to men as ordinary citizens and children, and only in lifestyle content. Among the structural features examined, only local distribution and a circulation less than 5,000 exhibit improvements in female representation. Ownership, distribution frequency, market position, and direct press support had little or no effect.

Formal Models of Conflicting Social Influence.

Social influence is the process in which an agent is under pressure to form her opinion on an issue based on the opinions expresses by her peers. An obvious reaction to social influence is to change ones opinions to conform to the pressure. The study of formal models of social influence has been drawing attention in the literature. A comparatively under-explored aspect of social influence is its role as an instrument of social network change. Agents with an eclectic milieu of peers might find themselves under conflicting social pressures. In this case to conform to social influence by changing one’s beliefs is no longer an option and the agent may seek to distance herself from some of her peers to relieve the pressure. We build a formal model of social influence that allows us to study social influence as a source of conflict and an instrument of network change. Within our framework different models of social influence can be defined but also compared to each other.

Arguably Argumentative: A Formal Approach to the Argumentative Theory of Reason

We propose a formal approach to the argumentative theory of reason, combining argumentation theory and modal logic in a novel way. We show that the resulting framework can be used to model important mechanisms identified by the theory, including how confirmation bias and other problematic modes of reasoning may in fact serve an important argumentative purpose that can give rise to classically sound conclusions through the process of social deliberation. We go on to suggest that the argumentative theory is based on an understanding of intelligent reasoning and rationality that sees these notions as irreducibly social, and that the argumentative theory itself provides a possible starting point in the search for new theoretical foundations based on this understanding. Moreover, we suggest that formal logic can aid in the investigation of foundational issues, and we sketch the development of an axiomatic approach to the study of rational deliberation.