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All-pay auctions, a common mechanism for various human and agent interactions, suffers (like many other mechanisms) from the possibility of players' failure to participate in the auction. The authors model such failures and fully characterize equilibrium for this class of games, presenting a symmetric equilibrium and showing that under some conditions the equilibrium is unique. They also reveal various properties of the equilibrium, such as the lack of influence of the most-likely-to-participate player on the behavior of the other players. The authors perform this analysis with two scenarios: the sum-profit model, in which the auctioneer obtains the sum of all submitted bids, and the max-profit model of crowdsourcing contests, in which the auctioneer can only use the best submissions and thus obtains only the winning bid. Finally, the authors examine various methods of influencing the probability of participation such as the effects of misreporting one's own probability of participating and how influencing another player's participation chances changes a player's strategy. [ABSTRACT FROM PUBLISHER]

As we saw in the first part of this short series, a mechanism design problem involves engineering the rules of a game so that, if participants then behave rationally in the game (by choosing strategies that maximize their expected utility, for example), then the result will satisfy some desired property. So far, however, we have said nothing about what these desirable properties might be, or what mechanisms might achieve them. Here, we will dig into these two issues in a little more detail. [ABSTRACT FROM AUTHOR]

We consider an automated agent that needs to coordinate with a human partner when communication between them is not possible or is undesirable ( tacit coordination games). Specifically, we examine situations where an agent and human attempt to coordinate their choices among several alternatives with equivalent utilities. We use machine learning algorithms to help the agent predict human choices in these tacit coordination domains. Experiments have shown that humans are often able to coordinate with one another in communication-free games, by using focal points, 'prominent' solutions to coordination problems. We integrate focal point rules into the machine learning process, by transforming raw domain data into a new hypothesis space. We present extensive empirical results from three different tacit coordination domains. The Focal Point Learning approach results in classifiers with a 40-80% higher correct classification rate, and shorter training time, than when using regular classifiers, and a 35% higher correct classification rate than classical focal point techniques without learning. In addition, the integration of focal points into learning algorithms results in agents that are more robust to changes in the environment. We also present several results describing various biases that might arise in Focal Point based coordination. [ABSTRACT FROM AUTHOR]

Multi-agent decision problems, in which independent agents have to agree on a joint plan of action or allocation of resources, are central to artificial intelligence. In such situations, agents' individual preferences over available alternatives may vary, and may try to reconcile these differences by voting. We consider scenarios where voters cannot coordinate their actions, but are allowed to change their vote after observing the current outcome, as is often the case both in offline committees and in online voting. Specifically, we are interested in identifying conditions under which such iterative voting processes are guaranteed to converge to a Nash equilibrium state—that is, under which this process is acyclic. We classify convergence results based on the underlying assumptions about the agent scheduler (the order in which the agents take their actions) and the action scheduler (the actions available to the agents at each step). By so doing, we position iterative voting models within the general framework of acyclic games and game forms. In more detail, our main technical results provide a complete picture of conditions for acyclicity in several variations of Plurality voting. In particular, we show that (a) under the traditional lexicographic tie-breaking, the game converges from any state and for any order of agents, under a weak restriction on voters' actions; and that (b) Plurality with randomized tie-breaking is not guaranteed to converge under arbitrary agent schedulers, but there is always some path of better replies from any initial state of the game to a Nash equilibrium. We thus show a first separation between order-free acyclicity and weak acyclicity of game forms, thereby settling an open question from [7] . In addition, we refute another conjecture of Kukushkin regarding strongly acyclic voting rules, by proving the existence of strongly acyclic separable game forms. [ABSTRACT FROM AUTHOR]

Abstract: We consider a simple model of cooperation among agents called Coalitional Skill Games (CSGs). This is a restricted form of coalitional games, where each agent has a set of skills that are required to complete various tasks. Each task requires a set of skills in order to be completed, and a coalition can accomplish the task only if the coalitionʼs agents cover the set of required skills for the task. The gain for a coalition depends only on the subset of tasks it can complete. We consider the computational complexity of several problems in CSGs, such as testing if an agent is a dummy or veto agent, computing the core and core-related solution concepts, and computing power indices such as the Shapley value and Banzhaf power index. [Copyright &y& Elsevier]

Abstract: The strategyproof classification problem deals with a setting where a decision maker must classify a set of input points with binary labels, while minimizing the expected error. The labels of the input points are reported by self-interested agents, who might lie in order to obtain a classifier that more closely matches their own labels, thereby creating a bias in the data; this motivates the design of truthful mechanisms that discourage false reports. In this paper we give strategyproof mechanisms for the classification problem in two restricted settings: (i) there are only two classifiers, and (ii) all agents are interested in a shared set of input points. We show that these plausible assumptions lead to strong positive results. In particular, we demonstrate that variations of a random dictator mechanism, that are truthful, can guarantee approximately optimal outcomes with respect to any family of classifiers. Moreover, these results are tight in the sense that they match the best possible approximation ratio that can be guaranteed by any truthful mechanism. We further show how our mechanisms can be used for learning classifiers from sampled data, and provide PAC-style generalization bounds on their expected error. Interestingly, our results can be applied to problems in the context of various fields beyond classification, including facility location and judgment aggregation. [Copyright &y& Elsevier]

Abstract: As autonomous agents proliferate in the real world, both in software and robotic settings, they will increasingly need to band together for cooperative activities with previously unfamiliar teammates. In such ad hoc team settings, team strategies cannot be developed a priori. Rather, an agent must be prepared to cooperate with many types of teammates: it must collaborate without pre-coordination. This article defines two aspects of collaboration in two-player teams, involving either simultaneous or sequential decision making. In both cases, the ad hoc agent is more knowledgeable of the environment, and attempts to influence the behavior of its teammate such that they will attain the optimal possible joint utility. [Copyright &y& Elsevier]