Jeroen Bruggeman

Community detection in networks with positive and negative links.

Detecting communities in complex networks accurately is a prime challenge, preceding further analyses of network characteristics and dynamics. Until now, community detection took into account only positively valued links, while many actual networks also feature negative links. We extend an existing Potts model to incorporate negative links as well, resulting in a method similar to the clustering of signed graphs, as dealt with in social balance theory, but more general. To illustrate our method, we applied it to a network of international alliances and disputes. Using data from 1993-2001, it turns out that the world can be divided into six power blocs similar to Huntingtons civilizations, with some notable exceptions.

Knowledge Specialization, Knowledge Brokerage and the Uneven Growth of Technology Domains

Why do certain domains of knowledge grow fast while others grow slowly or stagnate? Two distinct theoretical arguments hold that knowledge growth is enhanced by knowledge specialization and knowledge brokerage. Based on the notion of recombinant knowledge growth, we show that specialization and brokerage are opposing modes of knowledge generation, the difference between them lying in the extent to which homogeneous vs. heterogeneous input ideas get creatively recombined. Accordingly, we investigate how both modes of knowledge generation can enhance the growth of technology domains. To address this question, we develop an argument that reconciles both specialization and brokerage into a dynamic explanation. Our contention is that specializing in an increasingly homogeneous set of input ideas is both more efficient and less risky than brokering knowledge. Nevertheless, specializing implies progressively exhausting available recombinant possibilities, while brokerage creates new ones. Hence, technology domains tend to grow faster when they specialize, but the more specialized they become, the more they need knowledge brokerage to grow. We cast out our argument into five hypotheses that predict how growth rates vary across technology domains.

The social network, socioeconomic background, and school type of adolescent smokers

The aim of this study is to examine the role of Dutch second grade (age 13–14) high school peer networks in mediating socioeconomic background and school type effects on smoking behavior. This study is based on a longitudinal design with two measurement waves at five different high schools, of the complete networks of second grader friendships, as well as their smoking behavior, school type, and parents’ educational level. The analysis is done by simulation investigation for empirical network analysis (SIENA) modeling that can control for friendship selection on the basis of smoking similarity when assessing friends’ influence on smoking. The findings show that, when controlling for friendship selection, the influence of friends still plays a significant role in adolescent smoking behavior, and suggests that socioeconomic background and school type effects on smoking are mediated by the friendship networks at school.

Detecting Communities through Network Data

Social life coalesces into communities through cooperation and conflict. As a case in point, Shwed and Bearman (2010) studied consensus and contention in scientific communities. They used a sophisticated modularity method to detect communities on the basis of scientific citations, which they then interpreted as directed positive network ties. They assumed that a lack of citations implies disagreement. Some scientific citations, however, are contentious and should therefore be represented by negative ties, like conflicting relations in general. After expanding the modularity method to incorporate negative ties, we show that a small proportion of negative ties, commonly present in science, is sufficient to significantly alter the community structure. In addition, our research suggests that without distinguishing negative ties, scientific communities actually represent specialized subfields, not contentious groups. Finally, we cast doubt on the assumption that lack of cites would signal disagreement. To show the general importance of discerning negative ties for understanding conflict and its impact on communities, we also analyze a public debate.

Networks embedded in n-dimensional space: The impact of dimensionality change

Social networks can be embedded in an n-dimensional space, where the dimensions may reveal or denote underlying properties of interest. When the pertaining actors occupy niches of resources in this space, e.g., organizational niches of affiliates, we show there exists a non-monotonic effect of dimensionality change. Depending on niche width, relatively narrow or wide, dimensionality change has opposing effects on niche volume.

A logical toolkit for theory (re)construction

The social sciences have achieved highly sophisticated methods for data collection and analysis, leading to increased control and tractability of scientific results. Meanwhile, methods for systematizing these results, as well as new ideas and hypotheses, into sociological theories have seen little progress, leaving most sociological arguments ambiguous and difficult to handle, and impairing cumulative theory development. Sociological theory, containing many valuable ideas and insights, deserves better than this. As a way out of the doldrums, this paper presents a systematic approach to computer-supported logical formalization, that is widely applicable to sociological theory and other declarative discourse. By increasing rigor and precision of sociological arguments, they become better accessible to critical investigation, thereby raising scientific debate to a new level. The merits of this approach are demonstrated by applying it to an actual fragment from the sociological literature.

The Institutional Embeddedness of Social Capital: A Multilevel Investigation across 24 European Countries

This study contributes to earlier studies aimed at the question of whether the welfare state crowds out social capital or not by examining to what extent the welfare state affects the value of social capital. This article investigates the effects of three sources of social capital on occupational prestige and tests whether these effects are moderated by welfare state effort in terms of social spending. Multi-level analyses based on European Social Survey (ESS) 2002/03 and International Monetary Fund (IMF) data, including 39,299 people from 24 European countries, provides evidence that welfare state effort decreases the value of social capital.

The cricket and the ant : Organizational trade-offs in changing environments

Organizations face trade-offs when they adopt strategies in changing resource environments. The type of trade-off depends on the type of resource change. This paper offers an organizational trade-off model for quantitative resource changes. We call it the “Cricket and Ant” (CA) model, because the pertaining strategies resemble the cricket and ants behavior in La Fontaines famous fable. We derive theorems in this CA model in First Order Logic, which we also use to demonstrate that two theory fragments of organizational ecology, i.e., niche width theory and propagation strategy theory, obtain as variant cases of CA; their predictions on environmental selection preferences derive as theorems once their respective boundary conditions are represented in the formal machinery.

A note on structural holes theory and niche overlap

Diffuse competition due to niche overlap between actors without (direct) ties with each other, constrains their structural autonomy. This is not dealt with in Burt’s mathematical model of his well-known structural holes theory. We fix his model by introducing a network measure of niche overlap.

Dissecting discursive contention: A relational analysis of the Dutch debate on minority integration, 1990–2006

This paper elaborates a relational approach to examine discursive contention. We develop a network method to identify groups forming through contentious interactions as well as relational measures of polarization, leadership, solidarity and various aspects of discursive power. The paper analyzes how an assimilationist movement confronted its adversaries in the Dutch debate on minority integration. Over different periods in the debate, we find a recurrent pattern: a small yet cohesive group of challengers with strong discursive leaders forces their framing of integration issues upon other participants. We suggest that the pattern found in our study may exemplify a more universal network pattern behind discursive contention.