My scientific output
Centrality indices such as β-centrality, Katz status, and Hubbell’s index are commonly generalized to directed networks by relating the in-centrality of nodes to the in-centrality of their in-neighbors and equivalently so for out-centrality. This paper proposes an extension of Bonacich’s β-centrality…
Online political astroturfing—hidden information campaigns in which a political actor mimics genuine citizen behavior by incentivizing agents to spread information online—has become prevalent on social media. Such inauthentic information campaigns threaten to undermine the Internet’s promise to more equitable participation in public debates. We argue that the logic of social behavior within the campaign bureaucracy and principal–agent problems lead to detectable activity patterns among the campaign’s social media accounts…
Multivariate networks comprising several compositional and structural variables can be represented as multigraphs by various forms of aggregations based on vertex attributes. We propose a framework to perform exploratory and confirmatory multiplexity analysis of aggregated multigraphs in order to find relevant associations between vertex and edge attributes…
Scaling techniques such as the well known NOMINATE position political actors in a low dimensional space to represent the similarity or dissimilarity of their political orientation based on roll-call voting patterns. Starting from the same kind of data we propose an alternative, discrete, representation that replaces positions (points and distances) with niches (boxes and overlap)…
Signed two-mode networks have so far predominantly been analysed using blockmodeling techniques. In this work, we put forward the idea of projecting such networks onto its modes. Two projection methods are introduced which allow the application of known dichotomization tool for weighted networks to obtain a simple signed network…
Abstract Comparison of 8 disinformation campaigns on twitter APSA 2019 (poster)
Political astroturfing, a centrally coordinated disinformation campaign in which participants pretend to be ordinary citizens acting independently, has the potential to influence electoral outcomes and other forms of political behavior. Yet, it is hard to evaluate the scope and effectiveness of political astroturfing without ground truth information, such as the verified identity of its agents and instigators. In this paper, we study the South Korean National Information Service’s (NIS) disinformation campaign during the presidential election in 2012…
Centrality indices are a popular tool to analyze structural aspects of psychological networks. As centrality indices were originally developed in the context of social networks, it is unclear to what extent these indices are suitable in a psychological network context. In this article we critically examine several issues with the use of the most popular centrality indices in psychological networks…
Social networks can be made of various kinds of ties, but (often implicit) assumptions embodied in network-analytic tools do not necessarily apply to all of them. Centrality indices, or instance, build on the assumption that it is always beneficial to add more ties. While it has been noted that networks of ties with a negative sentiment require different concepts of centrality…
We present an alternative approach to assess centrality in networks which does not rely on traditional indices. The work is based on neighborhood-inclusion, a partial ranking inducing relation of nodes, which was shown to be preserved by many existing centrality indices. As such, it can serve as the shared basis for centrality in networks…
Network data consisting of recorded historical events can be represented as hypergraphs where the ties or events can connect any number of nodes or event related attributes. In this paper, we perform a centrality analysis of a directed hypergraph representing attacks by indigenous peoples from the Lesser Antilles on European colonial settlements, 1509–1700…
Various centrality indices have been proposed to capture different aspects of structural importance but relations among them are largely unexplained. The most common strategy appears to be the pairwise comparison of centrality indices via correlation. While correlation between centralities is often read as an inherent property of the indices, we argue that it is confounded by network structure in a systematic way…
This project investigates political astroturfing, i.e. hidden propaganda by powerful political actors aimed at mimicking grassroots activity, on social media. We focus on Twitter accounts used by the South Korean secret service to influence the 2012 presidential elections in favor of the eventual winner, Park Geun-hye…
In the social sciences, networks are used to represent relationships between social actors, be they individuals or aggregates. The structural importance of these actors is assessed in terms of centrality indices which are commonly defined as graph invariants. Many such indices have been proposed, but there is no unifying theory of centrality. Previous attempts at axiomatic characterization have been focused on particular indices, and the conceptual frameworks that have been proposed alternatively do not lend themselves to mathematical treatment…
The Centrality-Lethality Hypothesis states that proteins with a higher degree centrality are more likely to be lethal, i.e. proteins involved in more interactions are more likely to cause death when knocked off. This proposition gave rise to several new investigations in which stronger associations were obtained for other centrality measures. Most of this previous work focused on the well known protein-interaction network of Saccharomyces cerevisiae…