RESUMO

Critical thinking and skepticism are fundamental mechanisms that one may use to prevent the spreading of rumors, fake news, and misinformation. We consider a simple model in which agents without previous contact with the rumor, being skeptically oriented, may convince spreaders to stop their activity or, once exposed to the rumor, decide not to propagate it as a consequence, for example, of fact checking. We extend a previous, mean-field analysis of the combined effect of these two mechanisms, active and passive skepticism, to include spatial correlations. This can be done either analytically, through the pair approximation, or simulating an agent-based version on diverse networks. Our results show that while in mean field there is no coexistence between spreaders and susceptibles (although, depending on the parameters, there may be bistability depending on the initial conditions), when spatial correlations are included, because of the protective effect of the isolation provided by removed agents, coexistence is possible.

RESUMO

Innovation and evolution are two processes of paramount relevance for social and biological systems. In general, the former allows the introduction of elements of novelty, while the latter is responsible for the motion of a system in its phase space. Often, these processes are strongly related, since an innovation can trigger the evolution, and the latter can provide the optimal conditions for the emergence of innovations. Both processes can be studied by using the framework of evolutionary game theory, where evolution constitutes an intrinsic mechanism. At the same time, the concept of innovation requires an opportune mathematical representation. Notably, innovation can be modeled as a strategy, or it can constitute the underlying mechanism that allows agents to change strategy. Here, we analyze the second case, investigating the behavior of a heterogeneous population, composed of imitative and innovative agents. Imitative agents change strategy only by imitating that of their neighbors, whereas innovative ones change strategy without the need for a copying source. The proposed model is analyzed by means of analytical calculations and numerical simulations in different topologies. Remarkably, results indicate that the mixing of mechanisms can be detrimental to cooperation near phase transitions. In those regions, the spatial reciprocity from imitative mechanisms is destroyed by innovative agents, leading to the downfall of cooperation. Our investigation sheds some light on the complex dynamics emerging from the heterogeneity of strategy revision methods, highlighting the role of innovation in evolutionary games.

Assuntos

RESUMO

Feed restriction (FR) has been recognized as the major experimental assay able to retard aging and degeneration diseases, although the effects of dietary manipulation at Central Nervous System (CNS) superior functions as learning and memory remain controversial. The aim of the present study was to evaluate the FR effects in CNS superior functions focusing in learning and memory in rodent models. Male Wistar rats were divided into three groups (n = 9/group) according to dietary conditions: ad libitum (AL) with unlimited access to standard rat diet (22 percent of protein, 8 percent fiber, 4 percent fat, 10 percent minerals, 1.4 percent Calcium, 0.8 percent Phosphorus); FR30 and FR60 groups were fed with 70 percent and 40 percent, respectively, of total rat diet offered to the AL group for 15 weeks. The animals FR30 and FR60 showed significant increase of learning performance in Y maze compared to animals fed ad libitum. The FR30 group, in memory task, also showed strong preference to the correct arm in Y maze at the first trials and greater rightness probability, in relation to the AL and FR60 groups. The AL group had significantly higher exploratory activity at the open field test than both FR groups. These findings implicate the FR on modulation of CNS functions as learning, suggesting, also, a possible anxiogenic-like effect of stress caused by FR.

Assuntos