Ro’i Zultan

Causal responsibility and counterfactuals.

How do people attribute responsibility in situations where the contributions of multiple agents combine to produce a joint outcome? The prevalence of over-determination in such cases makes this a difficult problem for counterfactual theories of causal responsibility. In this article, we explore a general framework for assigning responsibility in multiple agent contexts. We draw on the structural model account of actual causation (e.g., Halpern & Pearl, 2005) and its extension to responsibility judgments (Chockler & Halpern, 2004). We review the main theoretical and empirical issues that arise from this literature and propose a novel model of intuitive judgments of responsibility. This model is a function of both pivotality (whether an agent made a difference to the outcome) and criticality (how important the agent is perceived to be for the outcome, before any actions are taken). The model explains empirical results from previous studies and is supported by a new experiment that manipulates both pivotality and criticality. We also discuss possible extensions of this model to deal with a broader range of causal situations. Overall, our approach emphasizes the close interrelations between causality, counterfactuals, and responsibility attributions.

Treating Equals Unequally: Incentives in Teams, Workers' Motivation and Production Technology

The importance of fair and equal treatment of workers is at the heart of the debate in organizational management. In this regard, we study how reward schemes and production technologies affect effort provision in teams. Our experimental results demonstrate that unequal rewards can potentially increase productivity by facilitating coordination and that the effect strongly interacts with the exact shape of the production function. Taken together, our data highlight the relevance of the production function for organization construction and suggest that equal treatment of equals is neither a necessary nor a sufficient prerequisite for eliciting high performance in teams.

Finding fault: Causality and counterfactuals in group attributions

Graphical abstract Highlights ► We develop a general framework of responsibility attributions in groups. ► Three experiments show that blame varies with the relationships between agents. ► Agents are blamed more if their complement succeeds rather than their substitute. ► Blame attributions are sensitive to ways in which an agent can make a difference. ► The importance of understanding responsibility attributions in groups is discussed.

Cycles of Conditional Cooperation in a Real-Time Voluntary Contribution Mechanism

This paper provides a new way to identify conditional cooperation in a real-time version of the standard voluntary contribution mechanism. We define contribution cycles as the number of contributors a player waits for before committing to a further contribution, and use a permutation test on contribution cycles to assign a measure of conditional cooperation to each group play. The validity of the measures is tested in an experiment. We find that roughly 20% of the plays exhibit dynamics of conditional cooperation. Moreover, notwithstanding a decline in contributions, conditional cooperation is found to be stable over time.

Auction mechanisms and bidder collusion: Bribes, signals and selection

The theoretical literature on collusion in auctions suggests that the first-price mechanism can deter the formation of bidding rings. In equilibrium, collusive negotiations are either successful or are avoided altogether, hence such analysis neglects the effects of failed collusion attempts. In such contingencies, information revealed in the negotiation process is likely to affect the bidding behavior in firstprice (but not second-price) auctions. We test experimentally a setup in which collusion is possible, but negotiations often break down and information is revealed in an asymmetric way. The existing theoretical analysis of our setup predicts that the first-price mechanism deters collusion. In contrast, we find the same level of collusion in first-price and second-price auctions. Furthermore, failed collusion attempts distort the bidding behavior in the ensuing auction, leading to loss of efficiency and eliminating the revenue dominance typically observed in first-price auctions.

Timing of messages and the Aumann conjecture: a multiple-selves approach

The Aumann (In: Gabszewicz JJ, Richard JF, Wolsey L (eds) Economic decision making: games, econometrics and optimisation, 1990) conjecture states that cheap-talk messages do not necessarily help to coordinate on efficient Nash equilibria. In an experimental test of Aumann’s conjecture, Charness (Games Econ Behav 33(2):177–194, 2000) found that cheap-talk messages facilitate coordination when they precede the action, but not when they follow the action. Standard game-theoretical modeling abstracts from this timing effect, and therefore cannot account for it. To allow for a formal analysis of the timing effect, I study the sequential equilibria of the signaling game in which the sender is modeled as comprising two selves: an acting self and a signaling self. I interpret Aumann’s argument in this context to imply that all of the equilibria in this game are ‘babbling’ equilibria, in which the message conveys no information and does not affect the behavior of the receiver. Using this framework, I show that a fully communicative equilibrium exists—only if the message precedes the action but not when the message follows the action. In the latter case, no information is transmitted in any equilibrium. This result provides a game-theoretical explanation for the puzzling experimental results obtained by Charness (2000). I discuss other explanations for this timing-of-message effect and their relationship to the current analysis.

Imperfect recall and time inconsistencies: an experimental test of the absentminded driver “paradox”

Absentmindedness is a special case of imperfect recall, in which a single history includes more than one decision node in an information set. Put differently, players, after making a decision, sometimes face it again without recalling having ‘been there before’. Piccione and Rubinstein (Game Econ Behav 20(1):3–24, 1997b) have argued that absentmindedness may lead to time inconsistencies. Specifically, in certain cases, a player’s optimal strategy as calculated when called to choose an action (the action stage) deviates from the optimal strategy as calculated in a preceding planning stage, although preferences remain constant and no new information is revealed between the two stages. An alternative approach assumes that the player maximizes expected payoff in the action stage while considering his actions at other decision nodes to be immutable. With this approach, no time inconsistencies arise. The present paper explores this issue from a behavioral point of view. We elicit participants’ strategies in an experimental game of absentmindedness, separately for a planning stage and an action stage. We find systematic and robust time inconsistencies under four variations of the experiment and using ten different parameterizations of the game. We conclude that real decisions under absentmindedness without commitment are susceptible to time inconsistencies.

We sing the praise of good displays: How gamblers bet in casino roulette

Gambling frequencies on single numbers in real casino roulette were displayed in a contour map. This resulted not only in a confirmation that gamblers are subject to middle bias, but also to accessibility effects. The figure allowed us to infer the location of the roulette wheel and croupier from the gambling data, as well as infer bounds on the dimensions of the roulette table.

When Nash Equilibria Can Be Self-Enforcing: A Multiple-Selves Approach to the Aumann Conjecture

The Aumann (1990) conjecture states that cheap-talk messages do not necessarily help to coordinate on efficient Nash equilibria. I use the example provided by Aumann to study the sequential equilibria of the signaling game in which the sender is modeled as comprising two selves: an acting self and a signaling self. I formalize Aumann’s argument in this context to imply that all of the equilibria in this game are ‘babbling’ equilibria, in which the message conveys no information and does not affect the behavior of the receiver. I show that a fully information-transmitting equilibrium exists — only if the message precedes the action but not when the message follows the action. In the latter case, no information is transmitted in any equilibrium. This result is consistent with, and provides an explanation for the experimental results obtained by Charness (2000). I discuss other explanations for this timing-of-message effect and their relationship to the suggested framework.