Specification of homophily in statistical network models: why similarity is not enough to represent homophily for numerical attributesProf. Tom Snijders (University of Groningen)
Tom A.B. Snijders is Professor of Statistics and Methodology at the Dept. of Sociology, University of Groningen, Emeritus Fellow, Nuffield College, University of Oxford and an Associate Member at the Dept. of Statistics, University of Oxford.
Homophily is a basic feature of social networks. For numerical actor variables, its specification in statistical network models is usually done by means of the absolute difference between ego and alter on the variable under consideration; sometimes, as an alternative, by the ego-alter interaction. It is argued that such specifications are incomplete for continuous actor variables and for ordinal numerical variables with three or more categories. The reason is that ego is not necessarily attracted mostly to others with the same value as ego; often the attraction is to some value between ego's value and the 'social norm'. (Attraction here is to be understood not necessarily as a preference, but rather as an empirical tendency.) Therefore, the usual representation will often amount to a misspecification. This is elaborated in an extension of the usual specification of effects of actor variables in stochastic actor-oriented models for network dynamics. This new specification may have consequences for results of studies of social selection. An example is given.
Dan McFarland is Professor of Sociology and Organizational Behavior at Stanford University. His research focuses on the social and organizational dynamics of educational systems like schools, classrooms and universities. In particular, Dan has performed a series of studies on classroom organization and interaction; on the formation of adolescent relationships, social structures, and identities; on interdisciplinary collaboration and intellectual innovation; and on relational sociology. His interdisciplinary collaborations with linguists and computer scientists are cutting-edge studies of big data and methodological advances in social networks and language modeling.
This paper attempts to directly consider the nature of relationships and the role of interaction dynamics more deeply. To this end, relationships are reconceptualized as a story between persons that is perceived (labeled), agreed upon, and enacted in interaction. From this perspective, types of ties like friendship are relational frameworks that are mutually recognized and enacted via certain interactional footings. To identify the effect of interactional footings over and above previously identified network mechanisms, we rely on systematic social observations of hundreds of settings that extend across one hundred thousand turns of social interaction, as well as longitudinally collected sociometric surveys and institutional records. With these data, interactions are not only coded for a variety of qualities, but they are situated in various social contexts and institutional framing efforts. For example, a particular interactional event, like the act of agreement between i and j at time t, can be embedded in a particular setting, a task (or sequence), a role-relation, and a reported friendship relation. Since most interactions are guided by any one or more of these framing efforts machine learning is employed to identify the interactions associated with each one while taking into account their overlap. Ultimately, the goal is to identify the interactional signal of a perceived and agreed upon reports of friendship. In such a fashion, we identify the interactional footings or ³friendship script² that actors employ to signal the relational frame of ³friendship². This signal - as a latent dimension - is then tested for its predictive capacity on friendship formation to ascertain if it has an effect over and above previously held mechanisms of tie formation.
Laura M. Koehly is Senior Investigator and Chief, Social and Behavioral Research Branch at the National Human Genome Research Institute. Her research focuses on developing and applying social network methods to the study of complex social systems, such as families and communities. In order to better understand the impact of the interpersonal environment on behaviors, Laura Koehly also develops statistical methods to examine the perspectives of all members within a family system, thereby considering the social context in which at-risk individuals live.
In the United States, approximately 66 million informal (unpaid) caregivers provide care to someone who is ill, disabled or are experiencing loss of function associated with aging; approximately 4.7 million perform such roles in Germany. These caregivers may be adult children, spouses, parents, or other social network members. Caregiving research has traditionally engaged a single-informant, primary caregiver approach to characterize the caregiving network composition and function. However, multiple family members are affected by caregiving and may experience it differently. In the current talk, we examine the added value of the multi-informant approach to characterize the social landscape of caregiving within the context of Alzheimer’s disease and related dementia (ADRD). Our data come from the Caregiving Roles and Expectations Networks (CaRENet) Project in which 72 informants from 30 families enumerated network members and indicated caregiving roles for each. We observe both within family and between family variability with respect to caregiving roles and expectations. These results provide evidence for moving beyond a sole primary caregiver model, suggesting the need to move towards a multi-informant approach when designing caregiving studies and interventions. In addition, network-level factors derived from such an approach may be important to family adaptation and caregiver well-being.
Dimitris' current research interests are on networks of political and business actors, political and policy entrepreneurship and social entrepreneur motivation. The unifying theme in his work is a focus on exceptional agency and relations as expressed in the networks of leaders and entrepreneurs.
Relations between agents (i.e. networks) act as conduits to their political power. And power is channeled to the attainment of governance outcomes. Traditional social science makes the simplifying assumption that actor preferences (their perceived utility) can be employed to predict their behaviour. By comparison an analysis of networks makes actor interdependence the point of departure to an understanding of their constraints and opportunities. In that respect actors can impact outcomes not only through their own discrete interventions, but also mediated by the pattern of interaction among others.
Governance as the product of political exchange is therefore affected by the quality of the interaction between political agents, what Jones and Robins et al. have termed governance embeddedness. For instance, the degree to which political agents reciprocate relations equitably, whether there is transitivity, and whether relations are predominantly hierarchical. Governance as a process is affected by the pattern of exchange between political actors. For instance, the degree to which there is a strong core-periphery, the multiplicity of clusters, prevalence of brokers or the skewness in the distribution of ties can affect the way politics is exercised and policies are created.
I employ a range of case studies of policy making, policy implementation and cross-border policy in Europe, to demonstrate how governance process and governance outcomes are affected by the networks of political agents. This often happens in ways that can only be comprehended by analyzing the pattern of actor relations. I also use examples that draw from cases of environmental policy and the recent debates on sustainability to hypothesize on the nature of governance resilience. This analysis is coached within the literature of leadership, political entrepreneurship and brokerage or what some have termed exceptional agency.
Auf dem Teerhof 58
Ulrik Brandes holds a Chair of Information Science at the University of Konstanz. Ulrik is a leading scholar in Social Network Analysis. His research interests are centered on graph drawing and information visualization, efficient graph algorithms and experimental algorithms. He is one of the editors of "Network Science" (Cambridge University Press) and serves as board member of the International Network for Social Network Analysis (INSNA). Currently he is conducting a Reinhart Koselleck project on the algorithmic foundations of network theory, a project in cooperation with the social sciences.
Visone (ital. mink) is a free software tool that combines comprehensive means for analysis with unique visualization capabilities. It can also be used as a graphical frontend to R, RSiena, and KNIME.
This is a hands-on introduction to visone. After a brief overview of its design and features, we will explore some of its core functionality. Using exemplary network analyses, we will produce presentations of findings step-by-step, starting from data input to arrive at publication quality information visualizations, including time-coherent animations of longitudinal networks.
It is advisable to bring a laptop running Windows, MacOS, or Linux. The software is written in Java and can be installed from www.visone.info. It features many standard and non-standard methods for analysis and visualization of networks, and a powerful graphical user interface. It's native file format is GraphML, allowing for arbitrarily many attributes of nodes, links, and networks, but other formats such as CSV tables, UCINet DL, Pajek .net, etc., can be imported. Visualizations can be exported as pdf, png, tiff, animated svg, or Windows metafiles.