1,720,965 research outputs found
Endogenous Diffusion in Social Networks. Two Cases: Infectious Diseases and Sharing of Knowledge
No full textComplex phenomena arising from the interaction of ``elemental'' pieces have been first studied in physics and biology, where such constitutive particles were given deterministic rules for their behavior. In that context it was already clear that even critical outcomes can result on the aggregate level in situations where agents' behaviors are ``mechanic'' and ``simple''.
In recent years, inspired by real-world phenomena, economics and other social sciences have also started to play a role in this very wide strand of research. On the one hand, by introducing degrees of rationality in agents' behaviors and, on the other hand, by allowing heterogeneity in their interactions and responses to endogenous and exogenous stimuli.
This kind of reasoning has proven itself of particular success when applied in the context of social networks. Research on such intrinsically complex objects blossomed naturally within the realm of sociology, however it was only with the advent of the Internet, with the availability of large databases and the application of mathematical techniques from statistical physics that the field has really started its golden period of prosperity.
In this dissertation we contribute to this strand of literature by focusing on diffusive mechanisms that naturally emerge in the context of social networks. The first example is provided by the contagion of diseases channeled through social contacts, with possible straightforward applications to the cases of diffusion of opinions or of bad habits. The second example under study is that of knowledge diffusion (sharing?), which is not only typical of the academic world but also of innovation-seeking environments, such as that of research-and-development firms, where a collaboration network is constituted by the individuals.
A common feature of these cases is the fact that economic agents can endogenously and dynamically adapt by changing their (local) network of contacts or their response. In both examples, though, the impact of a single agent's action can reverberate through the whole system via its contacts (and its contacts' contacts, and so on). In the context of social networks, then, it becomes particularly challenging to understand how local features (behaviors or inclinations) may propagate, amplify or dissolute when embedded in the whole environment. One crucial difference with other approaches lies exactly in the fact that ``local'' neighborhoods can indeed be very different from one another and, moreover, very different from the global situation, which is the outcome at an aggregate level.
This dissertation is structured as follows. The first chapter describes a model of diffusion of a disease between two different locations, where the agents are able to respond and adapt to this menace. A peculiarity of our model is the possibility of agents of deciding where (i.e. with whom) to interact, in the attempt of avoiding contagion while still obtaining the benefits coming from the interactions with other healthy agents. The analytical results show that such individual-level behaviors have crucially different outcomes depending on the ``world'' these agents are living in: in particular, the two globally different systems considered (one, ``globalized'', where connections between the locations are allowed and the other, ``autarkic'', where they are forbidden) exhibit crucially different resistance to exogenous shocks in the infection rate. Further research in this field is still needed, as this model is one of the few attempts in the economics literature at trying to embed rational and responsive agents in a dynamical model of diffusion on networks. Applications to systemic risk and systemic resistance can benefit from this kind of research as well as analyses of mechanisms where is prevalent the interplay between local versus global forces.
The second chapter deals with a classic dilemma in the economics and business literature, that of exploration versus exploitation, and links it to the achievement of results, i.e. to the notion of performance. Specifically, we follow individual scientists throughout their careers and use their co-authorship and citation networks to map their ``knowledge space'', in order to measure their propensity to explore, both in terms of new topics and of new collaborations. Econometric results shows that the relationship between exploration and performance tends to exhibit an inverted-U shape, hence supporting the theory that a ``sweet'' spot where performance is maximized might exist, at least at an individual level.
Further research on this topic is still necessary, for example to understand in depth the relationship existing (if any) between forms of ``social exploration'' (i.e. exploration in terms of collaborations and social contacts) and ``scientific exploration'' (i.e. in terms of changes of the subjects studied or fields of expertise). Moreover, the results and techniques developed here can not only be directly applied to bibliometrics studies, but can also be fundamental to give the right incentives (and, possibly, funding) to encourage long-term innovation-seeking behaviors.
The third chapter tackles the same research question, but from a different viewpoint: what is the outcome of that analysis when the production units are ``aggregated'' at the level of (departments of) universities? At this aggregate level, it turns out that, in contrast to what seen in the previous chapter, a U-shaped curve characterizes the relationship between performance and exploration. Moreover, this relationship is also complicated by the effects of resources and size of each university. This complication can be seen as evidence of how, at this level, the interplay between economies of scale and economies of scope can generate an overall complex behavior. In this case too, then, the individual-level and the aggregate-level analysis exhibit once again very different outcomes: this underlines even more the complexity that comes out from the interactions in systems composed by different layers and levels
La percezione del rischio al tempo dell’Infodemia: La risposta dei cittadini alle misure di contenimento
No full textLe misure di contenimento per l’epidemia di Coronavirus sono accettate e seguite in maniera differente dai cittadini. Mostriamo il perché ciò avviene con l’ausilio di un semplice modello di diffusione di percezioni ed opinioni in una rete sociale stilizzata. Infine, mostriamo che i dati del Ministero dell’Interno confermano che l’adeguarsi alle nuove normative e policy avviene, ma necessita di tempo
A Note on Matricial Ways to Compute Burt’s Structural Holes
Full text linkIn this note, I derive simple formulas based on the adjacency matrix of a network to compute measures associated with Ronald S. Burt’s structural holes (effective size, redundancy, local constraint, and constraint), together with the measure called improved structural holes introduced in 2017. This can help to see these measures within a unified computation framework because they can all be expressed in matricial form. These formulas can also be used to define naïve algorithms based on matrix operations for their computation. Such naïve algorithms can be used for small- and medium-sized networks, where exploiting the sparsity of the matrices and efficient triangle listing techniques are not necessary
Efficiency and Stability in a Process of Teams Formation
Full text linkMotivated by data on coauthorships in scientific publications, we analyze a
team formation process that generalizes matching models and network formation
models, allowing for overlapping teams of heterogeneous size. We apply
different notions of stability: myopic team-wise stability, which extends to
our setup the concept of pair-wise stability, coalitional stability, where
agents are perfectly rational and able to coordinate, and stochastic stability,
where agents are myopic and errors occur with vanishing probability. We find
that, in many cases, coalitional stability in no way refines myopic team-wise
stability, while stochastically stable states are feasible states that maximize
the overall number of activities performed by teams.Comment: 44 page
No-vaxxers are different in public good games
Full text linkIn September 2021 we conducted a survey to 1482 people in Italy, when the vaccination campaign against Covid19 was going on. In the first part of the survey we run three simple tests on players’ behavior in standard tasks with monetary incentives to measure their risk attitudes, willingness to contribute to a public good in an experimental game, and their beliefs about others’ behavior. In the second part, we asked respondents if they were vaccinated and, if not, for what reason. We classified as no-vaxxers those (around [Formula: see text] of the sample) who did not yet start the vaccination process and declared that they intended not to do it in the future. We find that no-vaxxers contribute less to the public good in the experimental game because they trust others less to do so. from the three tests we extrapolated a classification based on the benchmark of rationality and other-regarding preferences for each respondent, and we found that in this respect no-vaxxers do not differ from the rest of the population
Enhancing Institutional Trust: Evidence from an Experimental Study with Adolescents in Italy
No full textThis study presents a quantitative analysis of a randomized survey experiment with Italian high school students (N = 1,433). It aims to evaluate trust levels in various institutions-healthcare, education, politics, judiciary, and defense-and identify determinants influencing trust in the scientific field, particularly regarding health issues. Using experimental scenarios, potential causal relationships among factors influencing confidence and trust scores are explored. Three distinct experimental scenarios are included in the survey: the first examines the influence of various social media platforms, the second and the third evaluate the impact of doctors, parents, and friends on trust-building among young individuals. Our results indicate a high level of trust in science among adolescents and emphasize high confidence in scientific experts. The study provides policy insights aimed at fostering trust, including recommendations for investments in education, increased involvement of specialists in direct communication, and enhanced transparency measures to mitigate misinformation. © The Author(s), under exclusive licence to Springer Nature B.V. 2025
Does “network closure” beef up firms’ performance?
Full text linkIn this paper we study whether “network closure” in the supply chain can explain the heterogeneity observed in firms’ performance. Using unique panel data on trade flows among beef farms in the Italian region of Piedmont, we analyze a sequential supply chain characterized by the co-existence of two production goods: domestic cattle, of lower quality but less risky, and imported cattle, of higher quality but exposed to higher risks. Our findings indicate that network closure, a characteristic commonly linked to the enhancement of trustworthy relations and mutual cooperation, is associated with an increase in the performance of farms adopting the riskier production system. On the other hand, network closure does not affect the performance of farms using the more traditional and mature technology. Thus, trust may promote the use of inputs of superior quality.We acknowledge funding from the Italian Ministry of Education “Progetti di Rilevante Interesse Nazionale” (PRIN) grant 2017ELHNNJ
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
