Penélope Hernández

On the complexity of coordination

Many results on repeated games played by finite automata rely on the complexity of the exact implementation of a coordinated play of length n. For a large proportion of sequences, this complexity appears to be no less than n. We study the complexity of a coordinated play when allowing for a few mismatches. We prove the existence of a constant C such that if (m ln m)/n ≥ C, for almost any sequence of length n, there exists an automaton of size m that achieves a coordination ratio close to 1 with it. Moreover, we show that one can take any constant C such that C > e|X| ln |X|, where |X| is the size of the alphabet from which the sequence is drawn. Our result contrasts with Neyman (1997) that shows that when (m ln m)/n is close to 0, for almost no sequence of length n there exists an automaton of size m that achieves a coordination ratio significantly larger 1/|X| with it.

Heterogeneous network games: Conflicting preferences

In many economic situations, a player pursues coordination or anti-coordination with her neighbors on a network, but she also has intrinsic preferences among the available options. We here introduce a model which allows to analyze this issue by means of a simple framework in which players endowed with an idiosyncratic identity interact on a social network through strategic complements or substitutes. We classify the possible types of Nash equilibria under complete information, finding two thresholds for switching action that relate to the two-player setup of the games. This structure of equilibria is considerably reduced when turning to incomplete information, in a setup in which players only know the distribution of the number of neighbors of the network. For high degrees of heterogeneity in the population the equilibria is such that every player can choose her preferred action, whereas if one of the identities is in the minority frustration ensues.

A formal model based on Game Theory for the analysis of cooperation in distributed service discovery

New systems can be designed, developed, and managed as societies of agents that interact with each other by offering and providing services. These systems can be viewed as complex networks where nodes are bounded rational agents. In order to deal with complex goals, they require cooperation of the other agents to be able to locate the required services. The aim of this paper is formally and empirically analyze under which circumstances cooperation emerges in decentralized search of services. We propose a repeated game model that formalizes the interactions among agents in a search process where agents are free to choose between cooperate or not in the process. Agents make decisions based on the cost of their actions and the expected reward if they participate forwarding queries in a search process that ends successfully. We propose a strategy that is based on random-walks, and we study under what conditions the strategy is a Nash equilibrium. We performed several experiments in order to evaluate the model and the strategy and to analyze which network structures are more appropriate to promote cooperation.

Are social and entrepreneurial attitudes compatible?: A behavioral and self‐perceptional analysis

Purpose – The aim of this paper is to analyze the compatibility between entrepreneurial and social attitudes. Specifically, we analyze if subjects with a more developed economic entrepreneurial attitude exhibit a less social attitude. Design/methodology/approach – Our methodology integrates an economic experimental approach with a standard entrepreneurial intention questionnaire to analyze the interaction between entrepreneurial and social self-perceptions and behavior. Findings – There is empirical evidence that experimental entrepreneurial behavior (characterized by detecting an opportunity and accepting risk to take an economic advantage from it in laboratory experiments) reduces the incentive for social behavior. However, this effect does not appear if just self-perceptions instead of experimental behaviors are considered. Research limitations/implications – The social attitude of entrepreneurs may be overestimated in those empirical research studies based only on data obtained from entrepreneurs’ answers to hypothetical questions in a survey. Originality/value - To the best of our knowledge, this is the first paper presenting a laboratory experiment to represent the key features of entrepreneurial behavior instead of a case-control analysis to set differences in the experimental behavior of sub-samples of subjects defined in terms of their entrepreneurial motivation or experience.

Sequential versus Simultaneous Schelling Models: Experimental Evidence

This article shows the results of experiments where subjects play the Schelling’s spatial proximity model. Two types of experiments are conducted: one in which choices are made sequentially and a variation of the first where the decision making is simultaneous. The results of the sequential experiments are identical to Schelling’s prediction: subjects finish in a segregated equilibrium. Likewise, in the variant of the simultaneous decision experiment, the same result is reached: segregation. Subjects’ heterogeneity generates a series of focal points in the first round. To locate themselves, subjects use these focal points immediately, and as a result, the segregation takes place again. Furthermore, simultaneous experiments with commuting costs allow us to conclude that introducing positive moving costs does not affect segregation.

Hierarchy is Detrimental for Human Cooperation

Studies of animal behavior consistently demonstrate that the social environment impacts cooperation, yet the effect of social dynamics has been largely excluded from studies of human cooperation. Here, we introduce a novel approach inspired by nonhuman primate research to address how social hierarchies impact human cooperation. Participants competed to earn hierarchy positions and then could cooperate with another individual in the hierarchy by investing in a common effort. Cooperation was achieved if the combined investments exceeded a threshold, and the higher ranked individual distributed the spoils unless control was contested by the partner. Compared to a condition lacking hierarchy, cooperation declined in the presence of a hierarchy due to a decrease in investment by lower ranked individuals. Furthermore, hierarchy was detrimental to cooperation regardless of whether it was earned or arbitrary. These findings mirror results from nonhuman primates and demonstrate that hierarchies are detrimental to cooperation. However, these results deviate from nonhuman primate findings by demonstrating that human behavior is responsive to changing hierarchical structures and suggests partnership dynamics that may improve cooperation. This work introduces a controlled way to investigate the social influences on human behavior, and demonstrates the evolutionary continuity of human behavior with other primate species.

Guanxi, performance and innovation in entrepreneurial service projects

This paper analyzes the role played by two dimensions of entrepreneurs’ private social capital in the survival, growth and innovativeness of entrepreneurial service ventures: local size and preferential attachment degree. We build a bi-dimensional measure of social capital based on network models and a methodology to estimate this measure for any group of entrepreneurs. Based on a survey of service entrepreneurs who launched their business in the city of Shanghai, we show that roles played by each dimension are quite different. A large local size of the network increases the chances of survival of the new venture. However, the chance to become a dynamic venture is only related to entrepreneurs’ preferential attachment degree. This finding has relevant political and managerial implications.

Bounded Computational Capacity Equilibrium

A celebrated result of Abreu and Rubinstein (1988) states that in repeated games, when the players are restricted to playing strategies that can be implemented by finite automata and they have lexicographic preferences, the set of equilibrium payoffs is a strict subset of the set of feasible and individually rational payoffs. In this paper we explore the limitations of this result. We prove that if memory size is costly and players can use mixed automata, then a folk theorem obtains and the set of equilibrium payoffs is once again the set of feasible and individually rational payoffs. Our result emphasizes the role of memory cost and of mixing when players have bounded computational power.

Pragmatic languages with universal grammars

This paper constructs the equilibrium for a specific code that can be seen as a “universal grammar” in a class of common interest Sender–Receiver games where players communicate through a noisy channel. We propose a Senderʼs signaling strategy which does not depend on either the game payoffs or the initial probability distribution. The Receiverʼs strategy partitions the set of possible sequences into subsets, with a single action assignment to each of them. The Senderʼs signaling strategy is a Nash equilibrium, i.e. when the Receiver responds best to the Senderʼs strategy, the Sender has no incentive to deviate. An example shows that a tie-breaking decoding is crucial for the block-coding strategy to be an equilibrium. Efficiency is analyzed by comparing how close ex-ante expected payoffs are to those of noiseless communication. Moreover, we study how long communication should be to achieve a given payoff-approximation.

Modeling Local Social Migrations: A Cellular Automata Approach

In local social migrations, agents move from their initial location looking for a better local social environment. Social migrations processes do not change the number of social agents of a given type (i.e., the empirical distribution of the population) but their spatial location. Although cellular automata seems to appear as a natural approach to model of social migrations, the evolution of the configuration through a cellular automata might induce a new configuration wherein the number of agents of each type might be actually modified. This article provides a characterization of these cellular automata rules such that for any initial empirical distribution, the evolution of the configuration through a cellular automata of such class induces a new configuration with the same empirical distribution as the initial one, as required to model local social migrations. A class of sequences is defined in order to establish a sufficient condition to maintain this invariance property.