Christofer Edling

The web of human sexual contacts.

Promiscuous individuals are the vulnerable nodes to target in safe-sex campaigns.

Structure and time evolution of an Internet dating community

We present statistics for the structure and time evolution of a network constructed from user activity in an Internet community. The vastness and precise time resolution of an Internet community offers unique possibilities to monitor social network formation and dynamics. Time evolution of well-known quantities, such as clustering, mixing (degree-degree correlations), average geodesic length, degree, and reciprocity is studied. In contrast to earlier analyses of scientific collaboration networks, mixing by degree between vertices is found to be disassortative. Furthermore, both the evolutionary trajectories of the average geodesic length and of the clustering coefficients are found to have minima.

Sexual networks: implications for the transmission of sexually transmitted infections.

The structures of sexual networks are essential for understanding the dynamics of sexually transmitted infections. Standard epidemiological models largely disregard the complex patterns of intimate contacts. Social network analysis offers important insight into how to conceptualize and model social interaction and has the potential to greatly enhance the understanding of disease epidemics.

Korean university life in a network perspective: Dynamics of a large affiliation network

We investigate course registration data of 18 semesters at a Korean University to portray the time evolution of students’ positions in the network of fellow students. Apart from being a study of the social positions of students, the present work is also an example of how large-scale, time resolved, affiliation networks can be analyzed. For example, we discuss the proper definitions of weights, and propose a redefined weighted clustering coefficient. Among other things, we find that the students enter the network at the center and are gradually diffusing towards the periphery. On the other hand, the ties to the classmates of the first semester will, on average, become stronger as time progresses.

On network bipartivity

Systems with two types of agents with a preference for heterophilous interaction produce networks that are more or less close to bipartite. We propose two measures quantifying the notion of bipartivity. The two measures-one well known and natural, but computationally intractable, and the other computationally less complex, but also less intuitive-are examined on model networks that continuously interpolate between bipartite graphs and graphs with many odd circuits. We find that the bipartivity measures increase as we tune the control parameters of the test networks to intuitively increase the bipartivity, and thus conclude that the measures are quite relevant. We also measure and discuss the values of our bipartivity measures for empirical social networks (constructed from professional collaborations, Internet communities, and field surveys). Here we find, as expected, that networks arising from romantic online interaction have high, and professional collaboration networks have low, bipartivity values. In some other cases, probably due to low average degree of the network, the bipartivity measures cannot distinguish between romantic and friendship oriented interaction.

Friendship network characteristics and psychological well-being in late adolescence: Exploring differences by gender and gender composition

Aims: The aim of the present study was to examine the association between friendship networks and psychological well-being among 19-year-olds. Methods: The data used was a random sample of Swedish individuals born in 1990 who answered a questionnaire in 2009–2010. Friendship networks were considered in terms of three measures of emotional support. Six statements about the individual’s emotional state were used to create a summary measure of psychological well-being. Gender and gender composition were included as potentially moderating factors. The association between friendship networks and psychological well-being was analysed by means of linear regression analysis (n = 1289). Results: The results indicate that males’ and females’ friendship networks were similar with regard to quality and trust, whereas males’ networks were characterized by less self-disclosure and a stronger preference for same-gender friendships. Gender composition did not matter for the support levels. Emotional support was associated with psychological well-being but there were gender differences: females seemed to benefit more health-wise from having high-quality (and trusting) networks. Moreover, whereas self-disclosure among males was positively linked to well-being, this was not the case among females. None of these associations were moderated by gender composition. Conclusions: In sum, friendship networks are beneficial for the psychological well-being among late adolescents, but there are some important differences according to gender.

Neighborhood and Friendship Composition in Adolescence

The social surroundings in which an individual grows up and spends his or her everyday life have an effect on his or her life chances. Much of the research into this phenomenon focuses on so-called neighborhood effects and has put particular emphasis on the negative effects of growing up in a poor neighborhood. Originating from the sociological study of inner-city problems in the United States, the research has recently been embraced by Scandinavian social scientists, who have generally assessed the phenomenon with reference to social network effects and the lock-in effects of ethnic enclaves. We critique the theoretical assumptions that we find in recent Scandinavian research and argue that a straightforward interpretation of neighborhood effects in terms of network effects is problematic. Our argument is based on an empirical analysis of friendship circles of ninth graders in Stockholm (N = 240). We conclude that the friendship networks of ninth graders extend well beyond the neighborhood, thus casting serious doubt on the network effects assumption of previous research. We also conclude that there is nothing in the reality of these ninth graders that confirms the established concept of the ethnic enclave.

Peer clustering of exercise and eating behaviours among young adults in Sweden: a cross-sectional study of egocentric network data

BackgroundResearch suggests that the growing prevalence of obesity may be related to the influence of the health behaviours of peers. We look at clustering of exercise and eating behaviours amongst a previously unstudied group, young adults in Sweden. Previous research has mainly been conducted in the United States and Britain, countries that have relatively high rates of obesity.MethodsUsing ego-alter dyads from the egocentric network data as the unit of analysis, we conduct logistic regressions to investigate the association between ego and alter exercise and eating behaviours.ResultsRespondents have a significantly greater probability of engaging in regular exercise and eating healthily if a nominated peer also does so. Furthermore, the degree to which this behavior is shared is modulated by the strength of the relationship between the two individuals, with a greater probability of engaging in these behaviours observed when the relationship with the nominated peer is strong relative to when the relationship is weak. However, we find that ego-alter homogeneity in terms of gender and migration status was not associated with a significantly greater probability of behaving in a similar manner to a nominated peer. Furthermore, the status of the nominated peer as a relative or not did not impact the probability that the ego would engage in similar health behaviours to that alter.ConclusionsWe observe strong associations between ego and alter health behaviours for young adults, consistent with previous research. Although we cannot draw causal inferences, these results suggest that the health behaviours of an individual’s peers may play a role in shaping their own health behaviours.

The Phenomenology of Specialization of Criminal Suspects

A criminal career can be either general, with the criminal committing different types of crimes, or specialized, with the criminal committing a specific type of crime. A central problem in the study of crime specialization is to determine, from the perspective of the criminal, which crimes should be considered similar and which crimes should be considered distinct. We study a large set of Swedish suspects to empirically investigate generalist and specialist behavior in crime. We show that there is a large group of suspects who can be described as generalists. At the same time, we observe a non-trivial pattern of specialization across age and gender of suspects. Women are less prone to commit crimes of certain types, and, for instance, are more prone to specialize in crimes related to fraud. We also find evidence of temporal specialization of suspects. Older persons are more specialized than younger ones, and some crime types are preferentially committed by suspects of different ages.

Auf der Suche nach Identität

Wir bieten in diesem Beitrag eine kritische Betrachtung der Analytischen Soziologie, wie sie von Peter Hedstrom in seinem Buch „Dissecting the social“ (2005, dt. Anatomie des Sozialen, 2008) vorgestellt hat. Es ist fur uns von groster Wichtigkeit, schon an dieser Stelle zu bemerken, dass wir eine definitiv positive Einstellung gegenuber der Analytischen Soziologie haben. Wir beide sind in den 1990er Jahren unter Hedstroms Betreuung an der Stockholmer Universitat ausgebildet worden. In unserer eigenen Forschungstatigkeit streben wir ebenfalls danach, seinen Ansatz weiter zu verfolgen. Deswegen entsteht unsere Kritik grostenteils aus dem Wunsch heraus, das Programm weiter zu starken und sein bereits groses Potential noch besser nutzbar zu machen. Mit anderen Worten: Wir sehen es als erwiesen an, dass der von Hedstrom (2005) skizzierte Ansatz grundsatzlich der richtige Weg ist, ein signifikantes Verstandnis der sozialen Welt zu erzielen.