Publications

By Date

• Kaffai, M., Erhard, L., Richter, M. (Jan 9, 2026)

  Pop2net: Bipartite network generation for agent-based modeling

  Journal of Open Source Software

  DOI

  Abstract

  Agent-based modeling (ABM) is a scientific method used in fields such as social science, biology, and ecology to simulate interactions of autonomous agents and study the resulting emergent phenomena. The relationships between agents, which structure the simulated interactions, are often represented by network graphs. Since empirical data on networks is rare, many agent-based models rely on artificially generated networks (Amblard et al., 2015). Consequently, generating a valid network structure at the beginning of a simulation is critical. Additionally, accessing and modifying the network during the simulation are steps that must be managed in almost any agent-based model. Pop2net is a Python package that combines many steps related to network generation and management for ABM using a bipartite approach. Bipartite networks consist of two distinct types of entities where edges are only formed between entities of different types. In Pop2net, relationships are represented as bipartite networks connecting actors and locations. When two actors are linked to the same location, they are considered connected through that shared location. In this way, locations serve as a contact layer between actors, representing places where interactions occur or contexts that facilitate actor connections. The aim of Pop2net’s bipartite approach to relations is to simplify the generation and management of realistic network structures in ABM.
• Erhard, L., Hanke, S., Remer, U. , Falenska, A. & Heiberger, R. (Oct 1, 2024)

  PopBERT. Detecting Populism and Its Host Ideologies in the German Bundestag

  Political Analysis

  DOI

  Abstract

  The rise of populism concerns many political scientists and practitioners, yet the detection of its underlying language remains fragmentary. This paper aims to provide a reliable, valid, and scalable approach to measure populist rhetoric. For that purpose, we created an annotated dataset based on parliamentary speeches of the German Bundestag (2013–2021). Following the ideational definition of populism, we label moralizing references to “the virtuous people” or “the corrupt elite” as core dimensions of populist language. To identify, in addition, how the thin ideology of populism is “thickened,” we annotate how populist statements are attached to left-wing or right-wing host ideologies. We then train a transformer-based model (PopBERT) as a multilabel classifier to detect and quantify each dimension. A battery of validation checks reveals that the model has a strong predictive accuracy, provides high qualitative face validity, matches party rankings of expert surveys, and detects out-of-sample text snippets correctly. PopBERT enables dynamic analyses of how German-speaking politicians and parties use populist language as a strategic device. Furthermore, the annotator-level data may also be applied in cross-domain applications or to develop related classifiers.

  Replication Material 4 citations
• Raphael H. Heiberger, Lukas Erhard, Steffen Triebel and Alexander Brem (Jul 9, 2024)

  Creative Workers on the Move: How Cultural Fit to a New Organization Enhances Individual Performance

  Academy of Management Annual Meeting Proceedings

  DOI

  Abstract

  How does the arrival at a new work environment affect the performance of creative workers? Even though it is a shared experience in many careers, we know surprisingly little about the impact of transferring to an unfamiliar workplace. To test the direct and indirect effects of how creative workers fit new colleagues at scale, we need to have (i) information on career trajectories and (ii) assess the cultural fit (CF) to a work environment computationally. We address these challenges by collecting a unique dataset on early career researchers (ECR) and their transition to another university after graduating in physics and psychology between 2006 and 2015 in the US. Then, we measure the CF by utilizing unsupervised machine learning and comparing each ECR’s research to the work of their new colleagues. In a close approximation of both fields (> 2.5 million documents), our results not only show a strong impact of CF on creative performance but also that fitting-in moderates the trade-off between specialization and generalization strategies. Moreover, we reveal how high-status organizations impose social pressures that further augment the effects of CF.
• Erhard, L., Hanke, S., Remer, U. , Falenska, A. & Heiberger, R. (Sep 22, 2023)

  PopBERT. Detecting populism and its host ideologies in the German Bundestag

  arXiv

  DOI

  Abstract

  The rise of populism concerns many political scientists and practitioners, yet the detection of its underlying language remains fragmentary. This paper aims to provide a reliable, valid, and scalable approach to measure populist stances. For that purpose, we created an annotated dataset based on parliamentary speeches of the German Bundestag (2013 to 2021). Following the ideational definition of populism, we label moralizing references to the virtuous people or the corrupt elite as core dimensions of populist language. To identify, in addition, how the thin ideology of populism is thickened, we annotate how populist statements are attached to left-wing or right-wing host ideologies. We then train a transformer-based model (PopBERT) as a multilabel classifier to detect and quantify each dimension. A battery of validation checks reveals that the model has a strong predictive accuracy, provides high qualitative face validity, matches party rankings of expert surveys, and detects out-of-sample text snippets correctly. PopBERT enables dynamic analyses of how German-speaking politicians and parties use populist language as a strategic device. Furthermore, the annotator-level data may also be applied in cross-domain applications or to develop related classifiers.
• Erhard, L., & Heiberger, R. (Apr 1, 2023)

  Regression and Machine Learning

  Research Handbook on Digital Sociology

  DOI

  Abstract

  Machine learning (ML) techniques have become one of the most successful scientific tools and changed the everyday life of people around the globe (e.g., search engines). A vast amount of digital data sources on human behaviour has emerged due to the rise of the internet and opened the door for computer scientists to apply ML on social phenomena. In the social sciences, however, the adoption of ML has been less enthusiastic. To investigate the relation of traditional statistics and ML, this paper shows how ML might be used as regression analysis. For that purpose, we illustrate what a typical social science approach might look like and how using ML techniques could contribute additional insights when it comes to estimators (non-linearity) or the assessment of model fit (predictive power). In particular, we reveal how epistemological differences shape the potential usage of ML in the social sciences and discuss the methodological trade-off of applying ML compared to traditional statistics.

  Replication Material 2 citations
• Unger, S., Erhard, L., Wieczorek, O., Koß, C., Riebling, J., & Heiberger, R. (May 5, 2022)

  Benefits and detriments of interdisciplinarity on early career scientists’ performance. An author-level approach for U.S. physicists and psychologists

  PLOS ONE

  DOI

  Abstract

  Is the pursuit of interdisciplinary or innovative research beneficial or detrimental for the impact of early career researchers? We focus on young scholars as they represent an understudied population who have yet to secure a place within academia. Which effects promise higher scientific recognition (i.e., citations) is therefore crucial for the high-stakes decisions young researchers face. To capture these effects, we introduce measurements for interdisciplinarity and novelty that can be applied to a researcher’s career. In contrast to previous studies investigating research impact on the paper level, hence, our paper focuses on a career perspective (i.e., the level of authors). To consider different disciplinary cultures, we utilize a comprehensive dataset on U.S. physicists (n = 4003) and psychologists (n = 4097), who graduated between 2008 and 2012, and traced their publication records. Our results indicate that conducting interdisciplinary research as an early career researcher in physics is beneficial, while it is negatively associated with research impact in psychology. In both fields, physics and psychology, early career researchers focusing on novel combinations of existing knowledge are associated with higher future impact. Taking some risks by deviating to a certain degree from mainstream paradigms seems therefore like a rewarding strategy for young scholars.

  11 citations
• Wieczorek, O., Unger, S., Riebling, J., Erhard, L., Koß, C., & Heiberger, R. (Aug 1, 2021)

  Mapping the field of psychology: Trends in research topics 1995–2015

  Scientometrics

  DOI

  Abstract

  We map the topic structure of psychology utilizing a sample of over 500,000 abstracts of research articles and conference proceedings spanning two decades (1995–2015). To do so, we apply structural topic models to examine three research questions: (i) What are the discipline’s most prevalent research topics? (ii) How did the scientific discourse in psychology change over the last decades, especially since the advent of neurosciences? (iii) And was this change carried by high impact (HI) or less prestigious journals? Our results reveal that topics related to natural sciences are trending, while their ’counterparts’ leaning to humanities are declining in popularity. Those trends are even more pronounced in the leading outlets of the field. Furthermore, our findings indicate a continued interest in methodological topics accompanied by the ascent of neurosciences and related methods and technologies (e.g. fMRI’s). At the same time, other established approaches (e.g. psychoanalysis) become less popular and indicate a relative decline of topics related to the social sciences and the humanities.

  21 citations
• Erhard, L., Heiberger, R. & Windzio, M. (May 10, 2021)

  Diverse Effects of Mass Media Concerns about Immigration: New Evidence from Germany, 2001 - 2016

  SocArXiv

  DOI

  Abstract

  Media discourse is often seen as an important condition of people's attitudes and perceptions. Despite a rich literature, however, it is not well understood how media exposure influences attitudes towards immigrants. In contrast to previous studies, we argue that people rely on 'availability heuristics' shaped by mass media. From that point of view, it is the specific content of media discourse on immigration that affects people's concerns. We use 'Structural Topic Models' to classify media content of more than 24.000 articles of leading German newspapers from 2001 to 2016. Utilizing 'linear fixed effect models' allows us to relate a person's concern towards immigration as reported in the German Socioeconomic Panel to prevalent topics discussed in print media while controlling for several confounding factors (e.g., party preferences, interest in politics, etc.). We find a robust relationship between topic salience and attitudes towards integration. Our results also reveal that specific topics with negative contents (e.g., domestic violence) to increase concerns, while others (e.g., scientific studies, soccer) decrease concerns substantially, underlining the importance of available information provided by media. In addition, people with higher education are generally less affected by media salience of topics.

  4 citations
• Erhard, L., Heiberger, R. H., & Windzio, M. (Jan 8, 2021)

  Diverse Effects of Mass Media on Concerns about Immigration: New Evidence from Germany, 2001–2016

  European Sociological Review

  DOI

  Abstract

  Media discourse is often seen as an important condition of people’s attitudes and perceptions. Despite a rich literature, however, it is not well understood how media exposure influences attitudes towards immigrants. In contrast to previous studies, we argue that people rely on ‘availability heuristics’ shaped by mass media. From that point of view, it is the specific content of media discourse on immigration that affects people’s concerns. We use structural topic models to classify media content of more than 24,000 articles of leading German newspapers from 2001 to 2016. Utilizing linear fixed-effects models allows us to relate a person’s concern towards immigration, as reported in the German Socioeconomic Panel, to prevalent topics discussed in print media while controlling for several confounding factors (e.g., party preferences, interest in politics, etc.). We find a robust relationship between topic salience and attitudes towards integration. Our results reveal that specific topics with negative contents (e.g., domestic violence) increase concerns, while others (e.g., scientific studies, soccer) decrease concerns substantially, underlining the importance of available information provided by media. In addition, people with higher education are generally less affected by media salience of topics.

  19 citations