Conditionally exponential random models for individual properties and network structures: Method and application

Exponential random models have been widely adopted as a general probabilistic framework for complex networks and recently extended to embrace broader statistical settings such as dynamic networks, valued networks or two-mode networks. Our aim is to provide a further step into the generalization of this class of models by considering sample spaces which involve both families of networks and nodal properties verifying combinatorial constraints. We propose a class of probabilistic models for the joint distribution of nodal properties (demographic and behavioral characteristics) and network structures (friendship and professional partnership). It results in a general and flexible modeling framework to account for homophily in social structures. We present a Bayesian estimation method based on the full characterization of their sample spaces by systems of linear constraints. This provides an exact simulation scheme to sample from the likelihood, based on linear programming techniques. After a detailed analysis of the proposed statistical methodology, we illustrate our approach with an empirical analysis of co-authorship of journal articles in the field of neuroscience between 2009 and 2013.     

A new scalable leader-community detection approach for community detection in social networks

Studying social influence in networks is crucial to understand how behavior spreads. An interesting number of theories were elaborated to analyze how innovations and trends get adopted. The traditional view assumes that a minority of members in a society possess qualities that make them exceptionally persuasive in spreading ideas to others. These exceptional individuals drive trends on behalf of the majority of ordinary people. They are loosely described as being informed, respected, and well connected. The leaders or influential are responsible for the dissemination of information and the propagation of influence. In this paper, we propose a new scalable and a deterministic approach for the detection of communities using leaders nodes named Leader-Community Detection Approach LCDA. The proposed approach has two main steps. The first step is the leaders’ retrieval. The second step is the community detection using similarity between nodes. Our algorithms provide good results compared to ground truth membership community.     

Alternative estimation methods for identifying contagion effects in dynamic social networks: A latent-space adjusted approach

Contagion effects, also known as peer effects or social influence process, have become more and more central to social science, especially with the availability of longitudinal social network data. However, contagion effects are usually difficult to identify, as they are often entangled with other factors, such as homophily in the selection process, the individual’s preference for the same social settings, etc. Methods currently available either do not solve these problems or require strong assumptions. Following Shalizi and Thomas (2011), I frame this difficulty as an omitted variable bias problem, and I propose several alternative estimation methods that have potentials to correctly identify contagion effects when there is an unobserved trait that co-determines the influence and the selection. The Monte-Carlo simulation results suggest that a latent-space adjusted estimator is especially promising. It outperforms other estimators that are traditionally used to deal with the unobserved variables, including a structural equation based estimator and an instrumental variable estimator.     

The use of sparsest cuts to reveal the hierarchical community structure of social networks

We show that good community structures can be obtained by partitioning a social network in a succession of divisive sparsest cuts. A network flow algorithm based on fundamental principles of graph theory is introduced to identify the sparsest cuts and an underlying hierarchical community structure of the network via maximum concurrent flow. Matula [Matula, David W., 1985. Concurrent flow and concurrent connectivity in graphs. In: Alavi, Y., et al. (Eds.), Graph Theory and its Applications to Algorithms and Computer Science. Wiley, New York, NY, pp. 543–559.] established the maximum concurrent flow problem (MCFP), and papers on divisive vs. agglomerative average-linkage hierarchical clustering [e.g., Matula, David W., 1983. Cluster validity by concurrent chaining. In: Felsenstein, J. (Ed.), Numerical Taxonomy: Proc. of the NATO Adv. Study Inst., vol. 1. Springer-Verlag, New York, pp. 156–166 (Proceedings of NATO ASI Series G); Matula, David W., 1986. Divisive vs. agglomerative average linkage hierarchical clustering. In: Gaul, W., and Schader, M. (Eds.), Classification as a Tool of Research. Elsevier, North-Holland, Amsterdam, pp. 289–301; Thompson, Byron J., 1985. A flow rerouting algorithm for the maximum concurrent flow problem with variable capacities and demands, and its application to cluster analysis. Master Thesis. School of Engineering and Applied Science, Southern Methodist University] provide the basis for partitioning a social network by way of sparsest cuts and/or maximum concurrent flow.     

Weighting the transitivity of undirected weighted social networks with triadic edge dissimilarity scores

When an individual is socially connected to two others, the resulting triplet can be closed (if the two social partners are themselves connected) or open (if they are not connected). The proportion of closed triplets, referred to as the binary network transitivity, is a classic measure of the level of interconnectedness of a social network. However, in any given triplet, if the closing link is weak, or indeed if any of the links in the triplet is weak, then the triplet should not contribute as much to network transitivity as if all three links were equally strong. I propose two ways to weight the contribution of each triplet according to the dissimilarity between the three links in the triplet. Empirically, the resulting new metrics conveyed information not picked up by any other network-level metric. I envision that this approach could prove useful in studies of triadic mechanisms, i.e., situations where pre-existing social ties influence the interactions with third parties. These metrics could also serve as repeatable synthetic variables that summarize information about the variability of the strength of social connections.     

The analysis of multiple ties in longitudinal egocentric network data: A case study on bidirectional relationships between trust and drug use

We extend multi-level models to examine single egocentric network ties to the joint analysis of paired dynamic ties. Two analytic challenges are addressed. First, inference needs to account for multiple layers of nesting: ties are nested within pairs, pairs are nested within time points, and time points are nested within egos. Second, the focus is on the relationship between two dynamic ties; specification of outcome and predictor may be difficult. Instead, we treat both ties as outcomes. Our approach is used to analyze trust and reported drug use between egos and alters over time in a Bayesian framework.     

Norms,status and the dynamics of advice networks: A case study

The issue of the influence of norms on behavior is as old as sociology itself. This paper explores the effect of normative homophily (i.e. “sharing the same normative choices”) on the evolution of the advice network among lay judges in a courthouse. 0020 and 0025 social exchange theory suggests that members select advisors based on the status of the advisor. Additional research shows that members of an organization use similarities with others in ascribed, achieved or inherited characteristics, as well as other kinds of ties, to mitigate the potentially negative effects of this strong status rule. We elaborate and test these theories using data on advisor choice in the Commercial Court of Paris. We use a jurisprudential case about unfair competition (material and “moral” damages), a case that we submitted to all the judges of this court, to test the effect of normative homophily on the selection of advisors, controlling for status effects. Normative homophily is measured by the extent to which two judges are equally “punitive” in awarding damages to plaintiffs. Statistical analyses combine longitudinal advice network data collected among the judges with their normative dispositions. Contrary to what could be expected from conventional sociological theories, we find no pure effect of normative homophily on the choice of advisors. In this case, therefore, sharing the same norms and values does not have, by itself, a mitigating effect and does not contribute to the evolution of the network. We argue that status effects, conformity and alignments on positions of opinion leaders in controversies still provide the best insights into the relationship between norms, structure and behavior.     

Because they were there: Access,deliberation, and the mobilization of networks for support

When people need help, what is the process through which they decide whom in their network to turn to? Research on social support has described a process that is deliberative in nature: people determine their needs, assess who in their network has the needed attributes—such as skill, trustworthiness, intimacy, and accessibility—and then activate that tie. Nevertheless, research in behavioral economics and other fields has shown that people make many decisions not deliberatively but intuitively. We examine this possibility in the context of social support by focusing on one factor: accessibility. Although researchers have argued that people weigh the accessibility of potential helpers as they do any other attribute, accessibility may be not only an attribute of the helper but also a condition of the situation. We develop a framework to make this question tractable for survey research and evaluate competing hypotheses using original data on an analytically strategic sample of ∼2000 college students, probing concrete instances of social support. We identify and document not one but three decision processes, reflective, incidental, and spontaneous activation, which differ in the extent to which actors had deliberated on whether to seek help and on whom to approach before activating the tie. We find that while the process was reflective (consistent with existing theory) when skill or trustworthiness played a role, it was significantly less so (consistent with the alternative) when accessibility did. Findings suggest that actors decide whom in their network to mobilize through at least three systematically different processes, two of which are consistent less with either active “mobilization” or explicit “help seeking” than with responsiveness to opportunity and context.     

Developing a methodology to assess the impact of research grant funding: A mixed methods approach

This paper discusses the development of a mixed methods approach to analyse research funding. Research policy has taken on an increasingly prominent role in the broader political scene, where research is seen as a critical factor in maintaining and improving growth, welfare and international competitiveness. This has motivated growing emphasis on the impacts of science funding, and how funding can best be designed to promote socio-economic progress. Meeting these demands for impact assessment involves a number of complex issues that are difficult to fully address in a single study or in the design of a single methodology. However, they point to some general principles that can be explored in methodological design. We draw on a recent evaluation of the impacts of research grant funding, discussing both key issues in developing a methodology for the analysis and subsequent results. The case of research grant funding, involving a complex mix of direct and intermediate effects that contribute to the overall impact of funding on research performance, illustrates the value of a mixed methods approach to provide a more robust and complete analysis of policy impacts. Reflections on the strengths and weaknesses of the methodology are used to examine refinements for future work.     

A comparison of estimators for the network autocorrelation model based on observed social networks

Network autocorrelation models (NAMs) are widely used to study a response variable of interest among subjects embedded within a network. Although the NAM is highly useful for studying such networked observational units, several simulation studies have raised concerns about point estimation. Specifically, these studies have consistently demonstrated a negative bias of maximum likelihood estimators (MLEs) of the network effect parameter. However, in order to gain a practical understanding of point estimation in the NAM, these findings need to be expanded in three important ways. First, these simulation studies are based on relatively simple network generative models rather than observed networks, thereby leaving as an open question how realistic network topologies may affect point estimation in practice. Second, although there has been strong work done in developing two-stage least squares estimators as well as Bayesian estimators, only the MLE has received extensive attention in the literature, thus leaving practitioners in question as to best practices. Third, the performance of these estimators need to be compared using both bias and variance, as well as the coverage rate of each estimator's corresponding confidence or credible interval. In this paper we describe a simulation study which aims to overcome these shortcomings in the following way. We first fit real social networks using the exponential random graph model and used the Bayesian predictive posterior distribution to generate networks with realistic topologies. We then compared the performance of the three different estimators mentioned above.     

A model for the multiplex dynamics of two-mode and one-mode networks,with an application to employment preference,friendship, and advice

We propose a new stochastic actor-oriented model for the co-evolution of two-mode and one-mode networks. The model posits that activities of a set of actors, represented in the two-mode network, co-evolve with exchanges and interactions between the actors, as represented in the one-mode network. The model assumes that the actors, not the activities, have agency.     

The State of the Social Work Profession: A Systematic Review of the Literature on Antigay Bias

Antigay bias delimits the rights of sexual minorities. Given that the social work profession promotes social justice values, understanding the extent to which antigay bias exists within the profession is important. Two social work specific populations were included in this systematic literature review to capture the breadth of the profession: professionals and students. A total of 31 empirical articles met our inclusion criteria. Across the samples, social workers and students were found to have mostly positive attitudes toward gays and lesbians. The sociodemographic factors used to explain the variance in attitudes are reported, and suggestions for future research are provided.     

The potential of online social networking data for augmenting the study of high-risk personal networks among young men who have sex with men at-risk for HIV

Capturing dynamics in high-risk personal networks is essential for preventing HIV transmission. Online social networking data offer incentive to augment traditional selfreported approaches for network enumeration. To explore what online networks reveal about dynamics among high-risk associates, we examine the relationship between egocentric confidant and sex networks and personal Facebook friendship networks of a cohort of young Black men who have sex with men. Although overlap exists between self-reported and Facebook associates, the stabilities of each were unrelated. Confidants who were also Facebook friends with a respondent were, however, more likely to be retained. Thus, Facebook networks contain stable confidants.     

The power of activist networks in the mass self-communication era: A triangulation study of the impact of WikiLeaks on the stock value of Bank of America

This case study examines a confrontation between WikiLeaks and Bank of America (BOA). Drawing upon Castells’ concept of mass self-communication and the cocreational approach to public relations, a triangulation of social network analysis and event study method allows this project to capture the structure of WikiLeaks’ global network and to document how the activist network affected BOA's stock value. The analysis reveals that WikiLeaks emerged as the center of a global mass self-communication network consisting of a diverse group of members, such as social media sites and mass media outlets. The study offers implications for a re-conceptualization of the role of activism in public relations.     

Helping Young Children Cope with Community Violence: A Proposal for the Reduction of Social Distress in the Inner Cities

The authors discuss the crisis of violence in our society and its impact on young children. Research on early violence prevention is reviewed, and a rationale for building parent-teacher coalitions to attempt solutions to the problem of violence is presented. A curriculum for co-training ofparents and early childhood professionals in violence prevention is outlined. The need for longitudinal research on the implementation and impact of early violence prevention programs is noted.     

A visual methods approach for researching children’s perspectives: capturing the dialectic and visual reflexivity in a cross-national study of father-child interactions

ABSTRACT

The paper presents a visual methods approach from a cross national methodological project that used digital visual technologies to examine young children's perspectives in father-child interactions. The approach combines capturing the dialectic with visual reflexivity. The notion of ‘capturing the dialectic’ specifically by analysing conflict to gather the child’s intention as their perspective, is underpinned by finding the contradictions in a situation of which children are a part. Visual technologies and in particular digital film does this, because it can identify difference, as it observes and captures the dialectic process. Researchers collected between 5–10 hours of film footage and twenty-four film elicitation interviews from young children and their fathers in twelve families within England, Hong Kong, Norway and India. In the study, participants took footage of routine father-child interactions chosen by the children; and researchers sampled the footage for situations of conflict and emotionally charged moments in order to capture the dialectic. Researchers then conducted film elicitation interviews with the children and fathers, which were recorded for the purpose of visual reflexivity. This visual methods approach can support social science researchers to address differences in representation and truth, for a better understanding of a young child’s perspective in cross-national projects.     

Relearning to Live Life Without Substances: A Grounded Theory of the Impact of Group Physical Exercise on Sobriety

Research has found significant benefits in using exercise as an adjunct treatment for substance use. This study used a qualitative grounded theory approach to explore the role of group exercise on maintaining sobriety. Sixteen persons (13 White men and 3 White women, age M = 31.81, SD = 8.23), recruited from a substance use recovery group that meets at a gym in an urban area in the Southeast part of the United States, were individually interviewed. Data were analyzed using Charmaz’s (2006) constructivist grounded theory strategies. Central themes revealed a parallel process between the steps taken to seek sobriety and those taken to maintain sobriety. The driving forces of sobriety success in both was 12 steps and group exercise programming that included elements of mentorship, structure, accountability, and fellowship or community. This study supported the use of physical group exercise as an adjunct treatment option for substance use treatment.     

Mapping networks in corporate social responsibility communication on social media: A new approach to exploring the influence of communication tactics on public responses

Grounded in the networked stakeholder management theory and two-way communication, this study provides a snapshot of networks between companies and publics on Twitter in the context of corporate social responsibility (CSR) communication. Results showed that CSR communication activities (i.e., informing, retweeting, and mentioning) empowered a corporation through centralizing its network position and gaining public support (i.e., emotional, influencer, and knowledge support). In addition, degree centrality mediated the relationship between corporate retweets and stakeholder support and between corporate response and stakeholder support.     

Surrendering the environment for capital gain and Olson’s group theory: A case study of the dissolution of housing co-operative societies in Hong Kong

This paper describes the rise of the co-operative housing of civil servants and its fall during the transition of Hong Kong from a British colony to a special administrative region of the People’s Republic of China. Olson’s group theory was adopted to explain the timing of the dissolution in a context of uncertainty in the property rights of land; the terms of civil service appointments; and the housing market. The size of the ownership body and the value of the land were evaluated as factors affecting dissolution decisions. It was found that in agreement with Olson’s theory, the number of members of the body had a statistically significant positive relationship with the life (between formation and dissolution) of the co-operative body. In addition, it was also found that factors that affected the opportunity cost of maintaining status quo, including the value of the land on which the co-op scheme sits and the real option value of redevelopment, had a significant impact on the timing of the dissolution of the co-op. The implications for using Olson’s theory were also discussed.