Models for network dynamics: A Markovian framework

A question not very often addressed in social network analysis relates to network dynamics and focuses on how networks arise and change. It alludes to the idea that ties do not arise or vanish randomly, but (partly) as a consequence of human behavior and preferences. Statistical models for modeling changes in the structure of social networks are rare and often strongly restricted substantively. The common approach is to focus on conditional transition probabilities using loglinear modeling. In the present article it is argued that it is more natural to model transition rates instead of probabilities. A model for explaining transition rates is presented using continuous time Markov theory. It is shown that a Markovian approach yields a very flexible model that can handle a wide variety of parameters that may be structural non-structural or a combination. A range of possible models is discussed and applied to data on friendship formation in a classroom

Modeling social influence through network autocorrelation:constructing the weight matrix

Many physical and social phenomena are embedded within networks of interdependencies, the so-called 'context' of these phenomena. In network analysis, this type of process is typically modeled as a network autocorrelation model. Parameter estimates and inferences based on autocorrelation models, hinge upon the chosen specification of weight matrix W, the elements of which represent the influence pattern present in the network. In this paper I discuss how social influence processes can be incorporated in the specification of W. Theories of social influence center around 'communication' and 'comparison'; it is discussed how these can be operationalized in a network analysis context. Starting from that, a series of operationalizations of W is discussed. Finally, statistical tests are presented that allow an analyst to test various specifications against one another or pick the best fitting model from a set of models. (C) 2002 Elsevier Science B.V. All rights reserved

Evolution of friendship and best friendship choices

It has been recognized in the literature that the mechanisms driving friendship choices differ when different settings are considered. At the same time, it is likely that different types of friendships are governed by different mechanisms. Employing longitudinal sociometric data from classrooms in elementary schools, it is examined whether gender similarity, reciprocity, and proximity (joint membership of study groups) have similar effects on 'friendship' and 'best friendship' choices. The results suggest that children use loose definitions of 'friendship', as opposed to their definition of 'best friendship'. The networks resulting from these different choices are found to evolve according to (partly) different mechanisms. This especially holds for the effect of gender similarity, which is profoundly predominant in the 'best friend' networks, but loses much of this importance when 'friends' are also considered. Also, 'best friend' choices are much more stable. Reciprocity of choices is found to primarily be a by-product of the preference to chose friends of the same gender, rather than being an important choice criterion of itself

Social capital in organizations: From social structure to the management of corporate social capital

Abstract Social capital in general and the study of social capital in the context of organizations has gained considerable attention in recent years. Despite the promise in the potency of the concept, its useful application suffers from the plethora of different definitions and approaches-both theoretical and empirical. In this paper we build upon one unifying definition and attempt to provide an encompassing framework for corporate social capital-from both a theoretical and empirical point of view. We do this by explicitly distinguishing between social capital and social networks. Moreover, we distinguish between the positive (social capital) and negative (social liability) outcomes of social networks. Finally, we argue that it is imperative to consider the various organizational levels of analysis at which both social relationships and their outcomes (and antecedents) reside. (also downloadable) in electronic version: http://som.rug.nl/

Vertical and Horizontal Cross-Ties:Benefits of Cross-Hierarchy and Cross-Unit Ties for Innovative Projects

Social networks are an important driver for successful innovation, both at the individual level as well as the organizational level. Recent research has also shaped that networks within teams can enhance performance. Innovative project teams are embedded in an organizational context, however, and teams typically consist of people with expertise from diverse backgrounds, and from different units. Team members may have ties to other teams, business units, and hierarchical levels. Although it seems clear that such ties can influence team performance, remarkably little research has focused on what is here referred to as vertical and horizontal cross‐ties. Previous research may have ignored the possibility that vertical and horizontal bridging ties may have different performance outcomes. Although the literature suggests that diversity of input, or horizontal cross‐unit ties will benefit team performance and innovativeness, there is reason to believe that ties to higher levels in the organization might have an effect on project team performance and innovativeness too. This article in particular studies the role of vertical cross‐hierarchy ties. In an exploratory analysis combining quantitative and qualitative results, it is distinguished between horizontal cross‐unit and vertical cross‐hierarchy ties and their contribution to new business development (NBD) project performance, thereby making a substantial contribution to both academic literature and managerial practice. Our study is based on a multiple case‐study approach of several NBD project teams in a large European financial service provider. Our results show that successful innovation project teams are characterized by a large number of cross‐unit ties in combination with a large number of cross‐hierarchical ties compared with less successful project teams. Additionally, proof is found that vertical cross‐hierarchy ties should be concentrated rather than scattered across project members

The social network among engineering design teams and their creativity:A case study among teams in two product development programs

Since the creative product development task requires the teams to combine and integrate input from multiple other teams, the team's structure of interaction is an important determinant of their creativity. In this study we investigate different structural aspects of social networks of such team's and their creativity within two multinational product development programs (PDPs). There are two main results. First, teams with a wider range of informational links are better to realize creative novel and feasible output. Second, in contrast to prior findings our results indicate that network efficiency and the creativity of teams relate negatively. This suggests that direct contacts contribute much more to creativity than open network structures. In managerial terms our investigation indicates that the network structure of teams in PDPs is an important issue to consider when designing such programs and that tools should be available to assist their direct interaction. (C) 2009 Elsevier Ltd and IPMA. All rights reserved