Giangiacomo Bravo

Trust and Partner Selection in Social Networks: An Experimentally Grounded Model

This article investigates the importance of the endogenous selection of partners for trust and cooperation in market exchange situations, where there is information asymmetry between investors and trustees. We created an experimental-data driven agent-based model where the endogenous link between interaction outcome and social structure formation was examined starting from heterogeneous agent behaviour. By testing various social structure configurations, we showed that dynamic networks lead to more cooperation when agents can create more links and reduce exploitation opportunities by free riders. Furthermore, we found that the endogenous network formation was more important for cooperation than the type of network. Our results cast serious doubt about the static view of network structures on cooperation and can provide new insights into market efficiency.

Cultural Commons: A New Perspective on the Production and Evolution of Cultures

This compelling book offers a fresh and novel approach to study cultural and artistic expression from the perspective of ‘the commons’. It demonstrates how identifying cultures as shared resources is useful in eliciting the main factors and social dilemmas affecting the production and evolution of cultural expression.

Pillars of Trust: An Experimental Study on Reputation and Its Effects

This paper presents the results of laboratory experiments on the relevance of reputation for trust and cooperation in social interaction. We have extended a repeated investment game by adding new treatments where reputation is taken more explicitly into account than before. We then compared treatments where the investor and the trustee rate each other and treatments where the investor and the trustee were rated by a third party. The results showed that: (i) third party reputation positively affects cooperation by encapsulating trust; (ii) certain differences in the reputation mechanism can generate different cooperation outcomes. These results have interesting implications for the recent sociological debate on the normative pillars of markets.

Exit, Punishment and Rewards in Commons Dilemmas: An Experimental Study

Commons dilemmas are interaction situations where a common good is provided or exploited by a group of individuals so that optimal collective outcomes clash with private interests. Although in these situations, social norms and institutions exist that might help individuals to cooperate, little is known about the interaction effects between positive and negative incentives and exit options by individuals. We performed a modified public good game experiment to examine the effect of exit, rewards and punishment, as well as the interplay between exit and rewards and punishment. We found that punishment had a stronger effect than rewards on cooperation if considered by itself, whereas rewards had a stronger effect when combined with voluntary participation. This can be explained in terms of the ‘framing effect’, i.e., as the combination of exit and rewards might induce people to attach higher expected payoffs to cooperative strategies and expect better behaviour from others.

Hidden connections: Network effects on editorial decisions in four computer science journals

Abstract This paper aims to examine the influence of authors’ reputation on editorial bias in scholarly journals. By looking at eight years of editorial decisions in four computer science journals, including 7179 observations on 2913 submissions, we reconstructed author/referee-submission networks. For each submission, we looked at reviewer scores and estimated the reputation of submission authors by means of their network degree. By training a Bayesian network, we estimated the potential effect of scientist reputation on editorial decisions. Results showed that more reputed authors were less likely to be rejected by editors when they submitted papers receiving negative reviews. Although these four journals were comparable for scope and areas, we found certain journal specificities in their editorial process. Our findings suggest ways to examine the editorial process in relatively similar journals without recurring to in-depth individual data, which are rarely available from scholarly journals.

Large-scale effects of migration and conflict in pre-agricultural groups: Insights from a dynamic model

The debate on the causes of conflict in human societies has deep roots. In particular, the extent of conflict in hunter-gatherer groups remains unclear. Some authors suggest that large-scale violence only arose with the spreading of agriculture and the building of complex societies. To shed light on this issue, we developed a model based on operatorial techniques simulating population-resource dynamics within a two-dimensional lattice, with humans and natural resources interacting in each cell of the lattice. The model outcomes under different conditions were compared with recently available demographic data for prehistoric South America. Only under conditions that include migration among cells and conflict was the model able to consistently reproduce the empirical data at a continental scale. We argue that the interplay between resource competition, migration, and conflict drove the population dynamics of South America after the colonization phase and before the introduction of agriculture. The relation between population and resources indeed emerged as a key factor leading to migration and conflict once the carrying capacity of the environment has been reached.

Global food security and food riots – an agent-based modelling approach

Due to negative consequences of climate change for agriculture and food production shocks affecting different areas of the world, the past two decades saw the conditions of global food security increasingly worsen. This has resulted in negative consequences for the world economy, partly causing international food price spikes and social upheavals. In this paper we present statistical findings along with a preliminary version of an original agent-based model called the Dawe Global Security Model that simulates the global food market and the political fragility of countries. The model simulates the effects of food insecurity on international food prices and how these, coupled with national political fragility and international food trade can, in turn, increase the probability of food riots in countries. The agents in the model are the 213 countries of the world whose characteristics reflect empirical data and the international trade of food is also simulated based on real trade partnerships and data. The model has been informed, calibrated and validated using real data and the results of these procedures are presented in the paper. To further test the model we also present the model’s forecasts for the near future in terms of food prices and incidence of food riots. The Dawe Global Security Model can be used to test scenarios on the evolution of shocks to global food production and analyse consequences for food riots. Further developments of the model can include national responses to food crises to investigate how countries can influence the spread of global food crises.

Self-organization in the commons: An empirically-tested model

A appropriate bottom-up rule system can support the sustainability of common-pool resources such as forests and fisheries. The process that leads to the developments of such institutional settings requires the considerations of multiple social, physical, and institutional factors over long time horizons. In this paper, we present the SONICOM model as a general exploratory model of CPR systems. The model can be configured to represent different CPR systems in order to explore what kind of institutional settings result in stable systems, i.e. situations where the resource and the appropriators are in a state of well-being. We use a large-N-dataset of CPR management institutions to validate the model. The results show numerous correlations between various parameters of the system such as rule compliance, social influence and resource growth rate which help explaining the process of institutional emergence as well as unveiling the conditions under which systems are stable.

Intermediaries in Trust: Indirect Reciprocity, Incentives, and Norms

Any trust situation involves a certain amount of risk for trustors that trustees could abuse. In some cases, intermediaries exist who play a crucial role in the exchange by providing reputational information. To examine under what conditions intermediary opinion could have a positive impact on cooperation, we designed two experiments based on a modified version of the investment game where intermediaries rated the behaviour of trustees under various incentive schemes and different role structures. We found that intermediaries can increase trust if there is room for indirect reciprocity between the involved parties. We also found that the effect of monetary incentives and social norms cannot be clearly separable in these situations. If properly designed, monetary incentives for intermediaries can have a positive effect. On the one hand, when intermediary rewards are aligned with the trustor’s interest, investments and returns tend to increase. On the other hand, fixed monetary incentives perform less than any other incentive schemes and endogenous social norms in ensuring trust and fairness. These findings should make us reconsider the mantra of incentivization of social and public conventional policy.

Are two resources really better than one? Some unexpected results of the availability of substitutes

The possibility of exploiting multiple resources is usually regarded as positive from both the economic and the environmental point of view. However, resource switching may also lead to unsustainable growth and, ultimately, to an equilibrium condition which is worse than the one that could have been achieved with a single resource. We developed a dynamic model where users exploit multiple resources and have different levels of preference among them. In this setting, exploiting multiple resources leads to worse outcomes in both economic and ecological terms than the single resource case under a wide range of parameter configurations. Our arguments are illustrated using two empirical situations, namely oil drilling in the North Sea and whale hunting in the Antarctic.