Psychology

According to several authors Bion’s contribution has been a landmark in
thought and conceptualization of the unconscious functioning of human be-
ings in groups. In this paper we provide a mathematical model of group
behavior in which the members, depending on individual parameters, may
behave sharing to different degrees what is in Bion’s theory a common ba-
sic assumption. We discuss a formalization which combines both individual
characteristics and group dynamics. The state of each individual depends on
both the group state and each individual’s valency for the basic assumption.
By this formalization it is possible to analyze the group dynamics as
the result of the individual dynamics of the members and prove that, under
some conditions, each individual reproduces the group dynamics in a different
scale. In particular, we provide an example in which the chaotic behavior
that the group may exhibit is reflected in each member of the group. In this
case we are able to provide examples under which the nonlinear dynamics of
the group becomes chaotic.

A discrete-time dynamical system is proposed to model a class of binary choice games with externalities as those described by . In order to analyze some oscillatory time patterns and problems of equilibrium selection that were not considered in the qualitative analysis given by Schelling, we introduce an explicit adjustment mechanism. We perform a global dynamic analysis that allows us to explain the transition toward nonconnected basins of attraction when several coexisting attractors are present. This gives a formal explanation of some overshooting effects in social systems and of the consequent cyclic behaviors qualitatively described in . Moreover, we show how the occurrence of a global bifurcation may lead to the explanation of situations of path dependence and the creation of thresholds observed in real life situations of collective choices, leading to extreme forms of irreversible departure from an equilibrium and uncertainty about the long run evolution of the some social systems.

In this paper we discuss strategies concerning the implementation of an agent-based simulation of complex phenomena. The model we consider accounts for population decomposition and interaction in industrial districts. The approach we follow is twofold: on one hand, we implement progressively more complex models using different approaches (vertical multiple implementations); on the other hand, we replicate the agent-based simulation with different implementations using jESOF, JAS and plain C++ (horizontal multiple implementations). By using both different implementation approaches and a multiple implementation strategy, we highlight the benefits that arise when the same model is implemented on radically different simulation environments, comparing the advantages of multiple modeling implementations. Our findings provide some important suggestions in terms of model validation, showing how models of complex systems tend to be extremely sensitive to implementation details. Finally we point out how statistical techniques may be necessary when comparing different platform implementations of a single model. analyzes some common key features in the literature on geographical clusters, and in particular, on industrial districts [1] . She identifies, among the others, both "a dense network of inter-firm relationships, in which the firms cooperate and compete at the same time" and "a dense network of social relationships, based mainly on face to face contact, which is strictly inter-connected with the system of economic relationships." The first aspect is one we consider in our approach. In fact, starting from the definition given by where "industrial districts can be conceived as complex systems characterized by a network of interactions amongst heterogeneous, localized, functionally integrated and complementary firms," we introduce and model the role of workers interacting with firms.

This paper considers a model of industrial districts where different populations interact symbiotically. The approach consists in the parallel implementation of the model with jESOF, JAS and plain C++. We consider a district decomposition where two populations, workers and firms, cooperate while behaving independently. We can find interesting effects both in terms of worker localization consequences and of the dynamic complexity of the model, with policy resistance aspects. Those effects are stressed by comparing the dynamics of both the populations when they are independent one from each other and when they co-evolve.

Cournot oligopolies are the most frequently discussed economic models in the literature of mathematical economics. This research area was originated by Cournot , and based on his pioneering work, many scientists have introduced and examined the different variants of the classical Cournot model. A comprehensive summary of earlier works is given in and their multiproduct extensions and some applications are presented in . The most frequently discussed extensions are singleproduct models with product differentiation, multi-product oligopolies, labormanaged and rent-seeking games. The existence and uniqueness of the equilibria was the central research issue in the earlier years, and later the attention of scientists has been turned to the dynamic variants of these models. The asymptotic behavior of dynamic oligopolies became the main focus, first in the linear case and later nonlinearities have been introduced into the models. In most studies the total profits or the profits per labor units were the payoff functions of the firms, and no cooperation among the firms was assumed. In the noncooperative case the Nash-equilibrium is the solution of the static game and in most cases it is the steady state of the dynamic extensions. The equilibrium is a strategy vector such that no firm can improve its own payoff by unilaterally diverting from the equilibrium. However, the firms might be able to increase their payoffs by simultaneously moving away from the equilibrium, as it is well known in the case of prisoners' dilemma. Any simultaneous move of the firms requires some level of coordination, so some kind of cooperative effort has to be assumed. The cooperation of the firms may take many different forms, including information sharing, side payments, profit sharing, shareholding interlocks to mention a few. introduced the concept of partial cooperation, when each firm's payoff function is the sum of its own profit and certain proportions of the profits of its competitors. Chiarella and Szidarovszky (2005) examined dynamic oligopolies with partially cooperating firms under continuous time scales, their main focus was the loss of stability in the case of information delay. One common way to achieve partial cooperation is by cross shareholding.

Two different ways to model the diffusion of alternative choices within a population of individuals in the presence of social externalities are known in the literature. While Galam's model of rumors spreading considers a majority rule for interactions in several groups, Schelling considers individuals interacting in one large group, with payoff functions that describe how collective choices influence individual preferences. We incorporate these two approaches into a unified general discrete-time dynamic model for studying individual interactions in variously sized groups. We first illustrate how the two original models can be obtained as particular cases of the more general model we propose, then we show how several other situations can be analyzed. The model we propose goes beyond a theoretical exercise as it allows modeling situations which are relevant in economic and social systems. We consider also other aspects such as the propensity to switch choices and the behavioral momentum, and show how they may affect the dynamics of the whole population.

This paper introduces and analyzes a model of supervised work group where subordinates decide how to exert their effort in complementary tasks while the supervisors decide incentives. Incentives may be a combination of individual and group-based ones. The optimality of incentives is analyzed when considering two different cost functions for subordinates. The two cost functions describe different individual motivations; comparing the resulting effort allocations and production optimality, we can relate them to different organizational theories. Our results provide a measure of how motivation among subordinates may affect production and incentives. Furthermore, the optimal incentives schemes are examined in terms of Adams' equity theory.

In this paper we present a new framework to analyze the behavior of evolutionary 2 × 2 symmetric games. The proposed approach enanbles us to predict the dynamics of the system using the parameters of the game matrix above, without dealing with the concepts of Nash equilibria and evolutionary stable strategies. The predictions are in complete accordance with those that can be made with these latter concepts. Simulations have been performed on populations with spatial structures, and show a good agreement with the model's predictions. We also analyze the dynamics of a particular system, showing how effectively the framework applies to it.

Finite neighborhood repeated games with large number of players are examined. Each agent has the choice between two actions and its payoff depends on the number of other players with the same choice. We first showed that the number of different types of games is finite and then we derived tight upper bounds for the number of game types in the general case and also with monotonic and linear payoff functions. The different game types are identified by equivalence classes generated by canonical forms, and in the linear case a system of linear inequalities is derived that characterizes all games being equivalent to any given game. Numerical examples illustrate the theoretical results. Both bounded and unbounded examples are shown.

With the help of a simple Cournot model we show that a minority stake in a competitor, when internalized by its holder, decreases the equilibrium output of both firms and also of their competitors and raises operating profits for all of them; the anti-competitive effect is greater, the greater the stake. Furthermore, we show that holding a minority stake increases the likelihood of collusion for all firms. We test the validity of our model by performing an event study on a sample of same-industry acquisitions of minority stakes in large, listed American firms. Consistent with our predictions, we find that at the announcement of the transaction the shares of the target earn significantly positive extra returns and so does the industry average. JEL: L11, L12

Empirical evidence, and theoretical results have shown that, in an industry, higher concentration index indicates higher price-cost margin. In order to detect collusive behaviour the antitrust authorities often monitor the Herfindahl-Hirschman Index. We consider N-firm oligopolies where a group of firms partially cooperate with each other, and monitor the Herfindahl-Hirschman Index as well. After suspecting that the authorities might notice the violation of antitrust regulations, they stop their cooperation. The group will not cooperate again until the Index moves back to the legal domain. This flip-flop dynamical model is formulated, the equilibria are determined, and the asymptotic properties of the system are examined.

In this paper we consider a model where agents interact participating to projects in order to maximize their profit. We integrate the results of two human subjects experiments with the results of artificial agent simulations. A relevant feature emerging from the social dynamics of the human societies we analyzed is the aggregation in a single connected network of interacting individuals where some subjects play a social leader role. With our agent based simulation model we aim to identify some of the factors leading to the emergence of this aggregation phenomenon. In particular, the presence of both a behavioral rule allowing the agents to improve their projects and leaders acting as vehicles of mutual acquaintances seems to be extremely important.

Several recent contributions formalize and analyze binary choices games with externalities as those described by Schelling. Nevertheless, in the real world choices are not always binary, and players have often to decide among more than two alternatives. These kinds of interactions are examined in game theory where, starting from the well known rock-paper-scissor game, several other kinds of strategic interactions involving more than two choices are examined. In this paper we investigate how the dynamics evolve introducing one more option in binary choice games with externalities. The dynamics we obtain are always in a stable regime, that is, the structurally stable dynamics are only attracting cycles, but of any possible positive integer as period. We show that, depending on the structure of the game, the dynamics can be quite di¤erent from those existing when considering binary choices. The bifurcation structure, due to border 1 collisions, is explained, showing the existence of so-called big-bang bifurcation points.

In this paper we consider a model where agents interact participating to projects in order to maximize their profit. We integrate the results of two human subjects experiments with the results of artificial agent simulations. A relevant feature emerging from the social dynamics of the human societies we analyzed is the aggregation in a single connected network of interacting individuals where some subjects play a social leader role. With our agent based simulation model we aim to identify some of the factors leading to the emergence of this aggregation phenomenon. In particular, the presence of both a behavioral rule allowing the agents to improve their projects and leaders acting as vehicles of mutual acquaintances seems to be extremely important.