Research

Representative publications

Courses

Vita and Publications
 

Carol and Michael Lowenstein Term Professor

Professor of Philosophy and Legal Studies

Director: Philosophy, Politics, and Economics Program

tel: 215-898-5820
fax: 215-898-5576
office: 466 Logan Hall
email: cb36@sas.upenn.edu

Research Areas:

• Decision and Game Theory
• Social and Political Philosophy
• Behavioral Ethics
• Cognitive Science

My work has focused on several areas: the logical foundations of game theory, applications of game-theoretic and evolutionary models to distributed AI, and more recently - social norms and impersonal trust.

1. The nature and dynamics of social norms. I am interested in understanding how norms emerge and become stable, why an established norm may suddenly be abandoned, how is it possible that inefficient or unpopular norms survive, and what motivates people to obey norms. In order to answer some of these questions, I have combined evolutionary and game-theoretic tools with models of decision making drawn from cognitive and social psychology.  For example, I am developing a theory of context-dependent preferences that explains the observed variability in norm compliance and can be tested in experimental games that involve prosocial norms of fairness and reciprocity. 

The emergence of norms can be modeled in several ways, depending upon the type of norm that is investigated.  I have been interested in how unpopular descriptive norms such as "bad" fashions and fads may emerge as the result of negative informational cascades when agents are in the grip of 'pluralistic ignorance'.  Often what we call a social norm is a stable behavioral disposition that is supported by a variety of strategies.  Impersonal trust, for example, can evolve as a stable disposition in a population of conditionally "nice" agents.  A surprising result of this evolutionary model is that what we take to be unconditional moral norms can only survive in populations of conditional choosers. 

To study the decay of norms, I have focused on corruption phenomena, showing how and why systemic corruption can disappear rather suddenly, and under which circumstances corruption cycles may occur.

2. The logical foundations of game theory. In my past work I have analyzed the consequences of relaxing the 'common knowledge' assumption in several classes of games. My contributions include axiomatic models of players' theory of the game and the proof that -- in a large class of games -- a player's theory of the game is consistent only if the player's knowledge is limited. An important consequence of assuming bounded knowledge is that it allows for more intuitive solutions to familiar games such as the finitely repeated prisoner's dilemma or the chain-store paradox. I have also been interested in devising mechanical procedures (algorithms) that allow players to compute solutions for games of perfect and imperfect information. Devising such procedures is particularly important for AI applications, since interacting software agents have to be programmed to play a variety of 'games'.

3. Applications to distributed AI. Web agents are pieces of software that search the Internet for information, and then filter and process the retrieved information for their users. Image a large population of Web agents that send queries to various sites. An agent may adopt one of several strategies: it may send one query and wait for an answer, it may send a number of queries in succession, or it may send queries to all the relevant sites. If all agents adopt the latter strategy, however, the system is likely to jam. If agents 'cooperate',the outcome will be better for all. I am working with a group of computer scientists, game theorists and logicians to simulate different environments and strategy combinations to establish whether and under which conditions cooperation can evolve.

The Grammar of Society: the Nature and Dynamics of Social Norms, Cambridge University Press, 2006

The book examines social norms, such as fairness, cooperation, and reciprocity, in an effort to understand their nature and dynamics, generated expectations and evolution and change. Drawing on intellectual traditions and methods, including those of social psychology, experimental economics and evolutionary game theory, the book provides an integrated account of how social norms emerge and why and when we follow them. Examining the existence and survival of inefficient norms, the book demonstrates how norms evolve in ways that depend upon the psychological dispositions of the individual and how such dispositions may impair social efficiency.

Contents

1. The rule we live by; 2. Habits of the mind; 3. A taste for fairness; 4. Covenants without sword; 5. Informational cascades and unpopular norms; 6. The evolution of a fairness norm.

Rationality and Coordination, Cambridge University Press, 1993; Second edition, 1997. Italian edition, Feltrinelli, 1998

The book explores how individual actions coordinate to produce unintended social consequences. In the past this phenomenon has been explained as the outcome of rational, self-interested individual behaviour. I show that this is in no way a satisfying explanation. I discuss how much knowledge is needed by agents in order to coordinate successfully. If the answer is unbounded knowledge, then a whole variety of paradoxes arise. If the answer is very little knowledge, then there seems hardly any possibility of attaining coordination. The solution to coordination and cooperation is for agents to learn about each other. I conclude that rationality must be supplemented by models of learning and by an evolutionary account of how social order (i.e. spontaneous coordinated behaviour) can persist.

Contents

1. Rationality and predictability; 2. Equilibrium; 3. Epistemic rationality; 4. Self-fulfilling theories; 5. Paradoxes of rationality; 6. Learning and norms: the case of cooperation.

The Logic of Strategy, C. Bicchieri, R. Jeffrey and B. Skyrms (eds.), Oxford University Press, 1999

Edited by three leading figures in the field, this exciting volume presents cutting-edge work in decision theory by a distinguished international roster of contributors. These mostly unpublished papers address a host of crucial areas in the contemporary philosophical, study of rationality and knowledge. Topics include causal versus evidential decision theory, game theory, backwards induction, bounded rationality, counterfactual reasoning in games and in general analyses of the famous common knowledge assumptions in game theory and evaluations of the normal versus extensive form formulations of complex decision problems.

The Dynamics of Norms, C. Bicchieri, R. Jeffrey and B. Skyrms (eds.), cambridge University Press, 1997

In the social sciences norms are sometimes taken to play a key explanatory role. Yet norms differ from group to group, from society to society, and from species to species. How are norms formed and how do they change? This 'state-of-the-art' collection of essays presents some of the best contemporary research into the dynamic processes underlying the formation, maintenance, metamorphosis, and dissolution of norms. The volume combines formal modelling with more traditional analysis, and considers biological and cultural evolution, individual learning, and rational deliberation. In filling a significant gap in the current literature this volume will be of particular interest to economists, political scientists, and sociologists, in addition to philosophers of the social sciences.

Knowledge, Belief, and Strategic Interaction, C. Bicchieri and M.L. dalla Chiara (eds.), Cambridge University Press 1992

In recent years there has been a great deal of interaction among game theorists, philosophers, and logicians in certain foundational problems concerning rationality, the formalization of knowledge and practical reasoning, and models of learning and deliberation. This unique volume brings together the work of some of the preeminent figures in their respective disciplines, all of whom are engaged in research at the forefront of their fields. Together they offer a conspectus of the interaction of game theory, logic, and epistemology in the formal models of knowledge, belief, deliberation, and learning and in the relationship between Bayesian decision theory and game theory, as well as between bounded rationality and computational complexity.