Publications

Penalty shootouts are tough, but the alternating order is fair

Silvan Vollmer and David Schoch and Ulrik Brandes

We compare conversion rates of association football (soccer) penalties during regulation or extra time with those during shootouts. Our data consists of roughly 50,000 penalties from the eleven~most recent seasons in European men’s football competitions

Computational Reproducibility in Computational Social Science

David Schoch and Chung-hong Chan and Claudia Wagner and Arnim Bleier

In the last decade, replication and reproducibility crises have shaken the scientific landscape. As potential solutions, open science practices were heavily discussed and have been implemented with varying success in different disciplines. We argue, however, that the binary definition of reproducibility, specifically for computational-X disciplines such as computational social science, is insufficient since it is not explicit about the agents and conditions under which results can be reproduced.

The interplay of structural features and observed dissimilarities among centrality indices

David Schoch and Termeh Shafie

An abundance of centrality indices has been proposed which capture the importance of nodes in a network based on different structural features. While there remains a persistent belief that similarities in outcomes of indices is contingent on their technical definitions, a growing body of research shows that structural features affect observed similarities more than technicalities.

Rtoot: Collecting and Analyzing Mastodon Data

David Schoch and Chung-hong Chan

An implementation of calls designed to collect and organize Mastodon data via its Application Program Interfaces (API)

graphlayouts: Layout algorithms for network visualizations in R

The package graphlayouts implements several state-of-the-art algorithms which are so far not available for R. This includes algorithms for large graphs, to emphasize hidden group structures, and important nodes within a network.

RANG: Reconstructing reproducible R computational environments

Chung-hong Chan and David Schoch

A complete declarative description of the computational environment is often missing when researchers share their materials. Without such description, software obsolescence and missing system components can jeopardize computational reproducibility in the future, even when data and computer code are available. The R package rang is a complete solution for generating the declarative description

signnet: An R package for analyzing signed networks

A signed network is a network where both, positive and negative relationships may occur. Common network analytic tools are not applicable to such networks without adapting for the existence of negative ties. The R package signnet brings together methods that have been developed to analyze signed networks

netrankr: An R package for total, partial, and probabilistic rankings in networks

One of the key concepts in network science is network centrality. Centrality seeks to provide the answer to the question of who (or what) is important in a network depending on the underlying process forming the network and the empirical phenomenon in question….

An extended family of measures for directed networks

Martin Everett & David Schoch

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…

Coordination patterns reveal online political astroturfing across the world

David Schoch, Franziska B Keller, Sebastian Stier & JungHwan Yang

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…

Multiplexity analysis of networks using multigraph representations

Termeh Shafie & David Schoch

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…

Legislators’ roll-call voting behavior increasingly corresponds to intervals in the political spectrum

David Schoch & Ulrik Brandes

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)…

Projecting Signed Two-Mode Networks

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…

Political Astroturfing around the world

Franziska B Keller, David Schoch, Sebastian Stier & JungHwan Yang

Comparison of 8 disinformation campaigns on twitter

Political Astroturfing on Twitter: How to Coordinate a Disinformation Campaign

Franziska B Keller, David Schoch, Sebastian Stier & JungHwan Yang

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…

What do centrality measures measure in psychological networks?

Laura F Bringmann, Timon Elmer, Sacha Epskamp, Robert W Krause, David Schoch, Marieke Wichers, Johanna TW Wigman & Eveline Snippe

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 Stratification from Networks of Leveling Ties

David Schoch & Ulrik Brandes

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…

Centrality without indices: Partial rankings and rank probabilities in networks

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…

Hypergraph Representations: A Study of Carib Attacks on Colonial Forces, 1509-1700

Termeh Shafie, David Schoch Jimmy Mans, Corinne Hofman & Ulrik Brandes

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…

Correlations among centrality indices and a class of uniquely ranked graphs

David Schoch, Thomas Valente & Ulrik Brandes

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…

How to Manipulate Social Media: Analyzing Political Astroturfing Using Ground Truth Data from South Korea

Franziska B Keller, David Schoch, Sebastian Stier & JungHwan Yang

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…

Re-conceptualizing centrality in social networks

David Schoch & Ulrik Brandes

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…

Centrality as a Predictor of Lethal Proteins: Performance and Robustness

David Schoch & Ulrik Brandes

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…