The emergence of norms of cooperation in stag hunt games with production

In this paper we study a two agents asymmetric stag hunt game. The model has an infinity of strict, Pareto rankable Nash equilibria. The equilibrium selection problem is solved by appealing to the stochastic stability concept put forward by Young (1993). We prove two main results. When the action sets are numerable in.nite sets, then for any value of the distributive parameter we can expect the emergence of a norm involving less than maximal cooperation. When instead the action sets are finite sets of a particular type (in the sense that each agent can choose his maximum optimal effort and fractions of this), then for some value of the distributive parameter we can expect the emergence of a norm involving maximal cooperation

Egalitarianism. An evolutionary perspective

Two parties bargaining over a pie, the size of which is determined by their previous investment decisions. Investment costs are heterogeneous. The bargaining rule is sensitive to investment behavior. Two games are studied which differ for the considered sociopolitical structure: communal property in one case and private property in the other. We hereby show that in both games when a unique stochastically stable outcome exists a norm of investment and a norm of surplus division must coevolve. While the investment norm always supports the efficient investment profile, the surplus division norm may differ among these games depending on the size of investment cost gap. Under private property only the egalitarian surplus division evolves. Under communal property instead two different surplus division norms may evolve: the egalitarian one and an inegalitarian norm. We show that no cap to payoffs inequality emerges under private property while an inequality payoff cap endogenously evolves under communal property. The games have been proposed to explain the social norms used in modern hunter-gatherer societies

A remark on the experimental evidence from tacit coordination games

This paper proposes an interpretation of the experimental evidence on tacit coordination games involving randomly matched players provided by Van Huyck, Battalio and Beil (1990), based on the notion of stochastic stability. When the model is calibrated with the parameters chosen in the experiment, it predicts that every strict Nash equilibrium is stochastically stable; therefore, in the long run we should not observe the emergence of any particular pattern of behavior, as suggested by the experimental evidence. The model is also compatible with the experimental evidence provided by Goeree and Holt (2005)

On the coevolution of social norms in primitive societies

Two parties bargaining over a pie, the size of which is determined by their previous investment decisions. The bargaining rule is sensitive to investment behavior. Two games are considered. In both, bargaining proceeds according to the Nash Demand Game when a symmetric investments profile is observed. When, on the other hand, an asymmetric investments profile is observed, we assume that bargaining proceeds according to the Ultimatum Game in one case and according to a Dictator Game in the other. We hereby show that in both games when a unique stochastically stable outcome exists it supports an homogeneous behavior in the whole population both at the investment stage and at the distribution stage. A norm of investment and a norm of division must therefore coevolve in the two games, supporting both the efficient investment profile and the egalitarian distribution of the surplus, respectively. The two games differ depending on the conditions needed for the two norms to coevolve. The games are proposed to explain the social norms used in modern hunter-gatherer societies

On the co-evolution of investment and bargaining norms

Two parties bargaining over a pie, the size of which is determined by their previous investment decisions. The bargaining rule is sensitive to investment behavior. Two games are considered. In both, bargaining proceeds according to the Nash Demand Game when a symmetric investments profile is observed. When, on the other hand, an asymmetric investments profile is observed, we assume that bargaining proceeds according to the Ultimatum Game in one case and according to a Dictator Game in the other. We hereby show that in both games when a unique stochastically stable outcome exists it supports an homogeneous behavior in the whole population both at the investment stage and at the distribution stage. A norm of investment and a norm of division must therefore coevolve in the two games, supporting both the efficient investment profile and the egalitarian distribution of the surplus, respectively. The two games differ depending on the conditions needed for the two norms to coevolve. The games are proposed to explain the social norms used in modern hunter-gatherer societies

Glioblastoma multiforme: a multidisciplinary approach to overcome chemoresistance and find new therapeutic strategies

Objectives: Glioblastoma multiforme is the most frequent malignant brain tumor. Patients die within 15 months after diagnosis. The failure of current therapies is ascribed to a subpopulation of cells with stem-like properties, called glioma stem cells (GSCs). The aim of this study is to develop new effective therapies. Moreover, we want to better characterize the orthotopic xenograft model established by GSCs injection into NOD/SCID mice. Materials and methods: We tested Temolomide and Valproic acid treatments, alone and in combination, on seven GSC lines by MTT assay and we sequenced p53. Moreover, we characterized our xenograft model investigating the expression of stemness and differentiation markers by immunohistochemistry on FFPE tissues and by immunofluorescence on the correspondent cell line. Finally, we performed aCGH on the DNA extracted from the cell line and from FFPE tissues. Results: GSCs were resistant to Temozolomide and slightly sensitive to Valproic acid. The two drugs exerted a synergistic effect when combined performing a pre-conditioning with Valproic acid. Furthermore, several cell lines carry p53 mutations. IF and IHC showed a perfect correspondence for stemness markers expression, but discordant data for the others. aCGH analysis evidenced numerous alterations specific for the ex vivo sample, suggesting the presence of an in vivo clonal selection. Discussion: This work shows the importance of murine microenvironment in GSCs phenotype in vivo and suggests the possibility to use our combined treatment for therapeutic purposes. Conclusions: Orthotopic models from GSCs and in vitro grown cell lines represent good models for the development of GSC-targeted therapies

On the Co-Evolution of Investment and Bargaining Norms

Two parties bargaining over a pie, the size of which is determined by their previous investment decisions. The bargaining rule is sensitive to investment behavior. Two games are considered. In both, bargaining proceeds according to the Nash Demand Game when a symmetric investments profile is observed. When, on the other hand, an asymmetric investments profile is observed, we assume that bargaining proceeds according to the Ultimatum Game in one case and according to a Dictator Game in the other. We hereby show that in both games when a unique stochastically stable outcome exists it supports an homogeneous behavior in the whole population both at the investment stage and at the distribution stage. A norm of investment and a norm of division must therefore coevolve in the two games, supporting both the efficient investment profile and the egalitarian distribution of the surplus, respectively. The two games differ depending on the conditions needed for the two norms to coevolve. The games are proposed to explain the social norms used in modern hunter-gatherer societies

Adaptive Expectations Coordination in an Economy with Heterogeneous Agents

In this paper I study expectations coordination on the stationary state in a one-dimensional economy. I allow for two sources of heterogeneity: the first concerns the "fundamentals", the second concerns the adaptive learning rules. Specifically, I consider heterogeneous adaptive learning algorithm within a class of constant gain learning algorithm, where the parameter of gain differ across agents. We show that the interaction of these two sources of heterogeneity create difficulty to coordination. Our first result says that the condition for convergence of dynamics with learning in an economy with heterogeneity is equivalent to the condition for convergence in an economy with identical agents if and only if the partial derivative of the temporary equilibrium map with respect to agents' expectations are all of the same sign. Our second results say that when the signs of these partial derivatives are different across agents, there exist some regions in the parameters space in which convergence of dynamics with learning obtains under a kind of "corridor of stability". This means that, given the reaction coefficient of type 2 agents, coordination on the stationary state obtains if and only if the reaction coefficient of type 1 agents is neither too small nor too large. We give two examples concerning a cobweb and an overlapping generations economy.