Multilevel longitudinal analysis of social networks.

Stochastic actor-oriented models (SAOMs) are a modelling framework for analysing network dynamics using network panel data. This paper extends the SAOM to the analysis of multilevel network panels through a random coefficient model, estimated with a Bayesian approach. The proposed model allows testing theories about network dynamics, social influence, and interdependence of multiple networks. It is illustrated by a study of the dynamic interdependence of friendship networks and minor delinquency. Data were available for 126 classrooms in the first year of secondary school, of which 82 were used, containing relatively few missing data points and having not too much network turnover.

Social Support Associated with Condom Use Behavior Among Female Sex Workers in Iran.

BACKGROUND: Despite the widespread knowledge about social support and health, there is little information about the association between social support and HIV risk behaviors such as condom use among female sex workers (FSWs) in Iran. This study aimed to determine the association between social support and frequency of condom use among FSWs in Tehran, Iran. METHODS: Using mixed sampling methods, we recruited 170 FSWs in Tehran in 2017. We measured self-reported social support by face-to-face interviews using a standardized questionnaire. Linear regression was used to assess the association between socio-demographic characteristics (age, education level, marital status, and place of living), transactional sex characteristics (age at first transactional sex and frequency of transactional sex in the last month), HIV knowledge, social support network characteristics (social network size, duration of tie, intimacy, social support), and condom use behavior. RESULTS: Of the total of 1193 persons in FSW's social networks, 615 (51%) were sexual partners, 529 (44%) were peer sex workers, and 36 (5%) were family members. The participants perceived moderate social support from sexual partners, low from peer sex workers, and very low from family members. Adjusted for individual and other network characteristics, peer sex worker social support (b = 0.28, 95%CI 0.06, 0.50), and family support (b = 1.12, 95%CI 0.028, 2.23) were significantly associated with condom use. CONCLUSION: Family and peer sex worker social support are associated with condom use, but less strongly than HIV knowledge or place of living. However, very few FSWs are socially connected with families. Interventions to promote condom use among this vulnerable population should also consider social and familial support.

Determinants of safe sexual behavior of female sex workers in Tehran: the woman, her network, and the sexual partner.

BACKGROUND: Despite the steady growth of sexual transmission of HIV, there is little evidence about safe sexual behavior of FSWs, and social network effects on this behavior, in Iran. Our aim in this study was to determine the effect of social network characteristics on condom use among FSWs, considering individual characteristics of the FSWs and of their sexual partners, characteristics of their relationship, and the FSW's personal network. METHODS: A cross-sectional ego-centric network survey of 170 FSWs was carried out in Tehran between January and June 2017. A multilevel ordered logistic regression analysis was conducted to examine the effects of individual and relational characteristics simultaneously. RESULTS: Condom use in sexual relationships of the FSWs on average was rather low. Important determinants of safe sexual behavior were found both at the level of the individual FSW and at the level of the sexual partner. The main determinants at the level of the individual FSW were FSWs' age and HIV knowledge. At the level of the sexual partner, age and education of sexual partners, as well as intimacy, duration of tie, frequency of contacts with a given partner, frequency of contact, perceived social support, and perceived safe sex norms were significantly associated with condom use. CONCLUSIONS: The findings highlighted that considering only the individual characteristics of female sex workers is not sufficient for effectively promoting condom use. Factors at the network and dyadic level should also be considered, especially the role of sexual partners. Network-based interventions may be useful which modify social relationships to create a social environment that can facilitate changes in sexual behavior.

Modelling ambivalent triads in family research.

This research focuses on ambivalence in family networks and presents a framework for investigating how triadic configurations, beyond specific dyads, may affect individual outcomes such as well-being. First, the paper introduces the ambivalent triad census, counting the frequencies of 18 non-isomorphic triads in which ties can be positive, negative, or ambivalent, in non-directed networks, and proposes the linear combinations of three theoretical mechanisms (ambivalent balance, diffusion of stress, divide and conquer) predicting how embeddedness in an ambivalent triad may affect individual well-being. Second, the ambivalent triad census is applied to 300 non-directed family networks, 150 stepfamilies and 150 first-time families, in which mothers reported about the relationships with and between family members. Results show that mothers embedded in triads exhibiting more ambivalent balance and less diffusion of stress score higher on social self-esteem. The study emphasizes the importance of studying ambivalence in higher-level relational structures, such as triads, in families.

The Interplay Between Adolescents' Friendships and the Exchange of Help: A Longitudinal Multiplex Social Network Study.

The aim of this study was to unravel the interrelatedness of friendship and help, and to examine the characteristics of friendship and help networks. The effects of mutual versus one-sided help relations on friendship initiation and maintenance, and vice versa, were examined. Friendship and help networks were analyzed (N = 953 students; 41 classrooms; Mage  = 12.7). The results illustrate that friendship and help networks show some similarities, but only partly overlap and have distinct characteristics. Longitudinal multiplex social network analyses showed that mutual help was important for the maintenance of friendship, but not for the initiation of friendship. Further, particularly mutual friendships provided a context in which help took place. Implications of these findings are discussed.

Contemporaneous Statistics for Estimation in Stochastic Actor-Oriented Co-evolution Models.

Stochastic actor-oriented models (SAOMs) can be used to analyse dynamic network data, collected by observing a network and a behaviour in a panel design. The parameters of SAOMs are usually estimated by the method of moments (MoM) implemented by a stochastic approximation algorithm, where statistics defining the moment conditions correspond in a natural way to the parameters. Here, we propose to apply the generalized method of moments (GMoM), using more statistics than parameters. We concentrate on statistics depending jointly on the network and the behaviour, because of the importance of their interdependence, and propose to add contemporaneous statistics to the usual cross-lagged statistics. We describe the stochastic algorithm developed to approximate the GMoM solution. A small simulation study supports the greater statistical efficiency of the GMoM estimator compared to the MoM.

Self, peer, and teacher reports of victim-aggressor networks in kindergartens.

This study investigated if and how children and teachers differ in their assessment of victim-aggressor relationships in kindergartens. Self-, peer, and teacher reports of victimization-aggression networks (who is victimized by whom) were investigated in 25 Swiss kindergartens with 402 5- to 7-years-old. It was examined whether child characteristics (sex and parent-reported internalizing and externalizing behavior) influence informant reports of victimization and/or aggression. Findings from statistical network models indicated higher concordance between self and peer reports than between one of these and teacher reports. Results further showed more agreement among informants on aggressors than on victims. Aggressors reported by self and peer reports were low on internalizing behavior, and aggressors reported by self and teacher reports were high on externalizing behavior; teacher-reported victims were also high on externalizing behavior. Internalizing behavior was unrelated to victimization. According to self and peer reports, boys as well as girls were victimized by boys and girls equally; teachers reported less cross-sex victimization than same-sex victimization. The different views of teachers and children on victim-aggressor relationships have implications for the identification of aggression in early childhood. Mutual sharing of information between children, their parents, peers, and teachers may contribute to signaling victims and aggressors in the early school years.

HIV risk perception and sexual behaviors among female sex workers in Tehran, Iran.

Background: An adequate perception of the degree to which one is at risk of having or contracting HIV is necessary for behavioural change and the adoption of safe behaviours. There are limited data regarding HIV risk perceptions among female sex workers in Iran. This study aimed to determine the HIV risk perception status and its association with sexual behaviours among female sex workers in Tehran. Methods: A cross sectional study was conducted among 170 female sex workers in Tehran. Participants were recruited using a combination of snowball, purposeful, and convenience sampling methods. Multiple logistic regression was used to identify adjusted associations between background factors, sexual behaviours, and HIV risk perception. The analysis was conducted by the "logistf" package in the R statistical system. P-value less than .05 was considered as statistically significant. Results: Among the participants, 122 (77%) reported high HIV risk perception. Most female sex workers with high HIV risk perception reported that they did not consistently use condoms (n=120, 98%. Female sex workers with a higher frequency of sex work (AOR=1.18, 95% CI: 1.08, 1.31), inconsistent condom use (AOR=0.15, 95% CI: 0.02, 0.66), a history of HIV testing (AOR=5.1, 95% CI: 1.2, 26.0), and low HIV knowledge (AOR=0.97, 95% CI=0.95, 0.996) were more likely to report high HIV risk perception. Conclusion: Most female sex workers with risky sexual behaviours had a high HIV risk perception. Effective educational programs are suggested to enable female sex workers to correctly assess their own HIV risk and change risk behaviors based on self-assessment of actual risk.

Social network and HIV risk behaviors in female sex workers: a systematic review.

BACKGROUND: Social network characteristics have an important role in understanding HIV transmission among female sex workers. The purpose of this systematic review was to summarize and critically appraise the existing studies on the social network characteristics and HIV risk behaviors among female sex workers. METHOD: A systematic review was performed using predefined eligibility criteria through searching electronic databases. Two independent reviewers assessed the methodological quality of studies. RESULTS: Nineteen papers met the eligible review criteria. The synthesized evidence suggests that characteristics of social networks, especially functional characteristics such as social support and social capital, are important constructs for understanding the HIV risk behaviors. CONCLUSIONS: The findings of the present review enhance our understanding of the role of social network characteristics in HIV risk behaviors among female sex workers. However, the findings also highlighted a dearth of knowledge about the association of structural characteristics of social networks with HIV risk behaviors among female sex workers.

Popularity Breeds Contempt: The Evolution of Reputational Dislike Relations and Friendships in High School.

In this study, we examined the dynamics of the perception of "dislike" ties (reputational dislike) among adolescents within the contexts of friendship, perceived popularity, substance use, and Facebook use. Survey data were collected from a longitudinal sample of 238 adolescents from the 11th and 12th grades in one California high school. We estimated stochastic actor-based network dynamic models, using reports of reputational dislike, friendships, and perceived popularity, to identify factors associated with the maintenance and generation reputational dislike ties. The results showed that high-status adolescents and more frequent Facebook users tended to become perceived as or stay disliked by their peers over time. There was a tendency for friendships to promote the creation and maintenance of reputational disliking but not vice versa. Adolescents tended to perceive others as disliked when their friends also perceived them as disliked. There was no evidence that either cigarette smoking or drinking alcohol affected reputational dislike dynamics. This study highlights the important role that the hierarchical peer system, online peer context, and friendships play in driving information diffusion of negative peer relations among adolescents.

Representing Micro-Macro Linkages by Actor-Based Dynamic Network Models.

Stochastic actor-based models for network dynamics have the primary aim of statistical inference about processes of network change, but may be regarded as a kind of agent-based models. Similar to many other agent-based models, they are based on local rules for actor behavior. Different from many other agent-based models, by including elements of generalized linear statistical models they aim to be realistic detailed representations of network dynamics in empirical data sets. Statistical parallels to micro-macro considerations can be found in the estimation of parameters determining local actor behavior from empirical data, and the assessment of goodness of fit from the correspondence with network-level descriptives. This article studies several network-level consequences of dynamic actor-based models applied to represent cross-sectional network data. Two examples illustrate how network-level characteristics can be obtained as emergent features implied by micro-specifications of actor-based models.

Scientific collaboration dynamics in a national scientific system.

This paper examines the collaboration structures and dynamics of the co-authorship network of all Slovenian researchers. Its goal is to identify the key factors driving collaboration and the main differences in collaboration behavior across scientific fields and disciplines. Two approaches to modelling network dynamics are combined in this paper: the small-world model and the mechanism of preferential attachment, also known as the process of cumulative advantage. Stochastic-actor-based modelling of co-authorship network dynamics uses data for the complete longitudinal co-authorship networks for the entire Slovenian scientific community from 1996 to 2010. We confirmed the presence of clustering in all fields and disciplines. Preferential attachment is far more complex than a single global mechanism. There were two clear distinctions regarding collaboration within scientific fields and disciplines. One was that some fields had an internal national saturation inhibiting further collaboration. The second concerned the differential impact of collaboration with scientists from abroad on domestic collaboration. In the natural, technical, medical, and biotechnical sciences, this promotes collaboration within the Slovenian scientific community while in the social sciences and humanities this inhibits internal collaboration.

Antisocial Behavior Trajectories and Social Victimization Within and Between School Years in Early Adolescence.

Antisocial behavior typically increases during early adolescence, but the possibility of seasonal variation has not been examined. In this study, trajectories of antisocial behavior were estimated for early adolescent boys and girls. Data were obtained from a 3-year longitudinal study of 11 middle schools in the western U.S. (n = 5,742), with assessments completed four times per academic year. Antisocial behavior increased steadily throughout 6th grade, but beginning in 7th grade for boys and 8th grade for girls, it declined during the school year. Significant increases between grades 6-7 and 7-8 were found for both genders. Trajectories varied by contextual and individual-level social victimization and gender. Implications for theoretical development and future studies are discussed.

Victims, bullies, and their defenders: a longitudinal study of the coevolution of positive and negative networks.

The complex interplay between bullying/victimization and defending was examined using a longitudinal social network approach (stochastic actor-based models). The (co)evolution of these relations within three elementary schools (Grades 2-5 at Time 1, ages 8-11, N = 354 children) was investigated across three time points within a year. Most bullies and defenders were in the same grade as the victims, although a substantial number of bullies and defenders were in other grades (most often one grade higher). Defenders were usually of the same gender as the victims, whereas most bullies were boys, with boys bullying both boys and girls. In line with goal-framing theory, multiplex network analyses provided evidence for the social support hypothesis (victims with the same bullies defended each other over time) as well as the retaliation hypothesis (defenders run the risk of becoming victimized by the bullies of the victims they defend). In addition, the analysis revealed that bullies with the same victims defended each other over time and that defenders of bullies initiated harassment of those bullies' victims. This study can be seen as a starting point in unraveling the relationship dynamics among bullying, victimization, and defending networks in schools.

Onset to First Alcohol Use in Early Adolescence: A Network Diffusion Model.

A novel version of Snijders's stochastic actor-based modeling (SABM) framework is applied to model the diffusion of first alcohol use through middle school-wide longitudinal networks of early adolescents, aged approximately 11-14 years. Models couple a standard SABM for friendship network evolution with a proportional hazard model for first alcohol use. Meta-analysis of individual models for 12 schools found significant effects for friendship selection based on the same alcohol use status, and for an increased rate of onset to first use based on exposure to already-onset peers. Onset rate was greater at higher grades and among participants who spent more unsupervised time with friends. Neither selection nor exposure effects interacted with grade, adult supervision, or gender.

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 empirical value of the model is demonstrated by examining how employment preferences co-evolve with friendship and advice relations in a group of seventy-five MBA students. The analysis shows that activity in the two-mode network, as expressed by number of employment preferences, is related to activity in the friendship network, as expressed by outdegrees. Further, advice ties between students lead to agreement with respect to employment preferences. In addition, considering the multiplexity of advice and friendship ties yields a better understanding of the dynamics of the advice relation: tendencies to reciprocation and homophily in advice relations are mediated to an important extent by friendship relations. The discussion pays attention to the implications of this study in the broader context of current efforts to model the co-evolutionary dynamics of social networks and individual behavior.

Does Proximity Matter? Distance Dependence of Adolescent Friendships.

Geographic proximity is a determinant factor of friendship. Friendship datasets that include detailed geographic information are scarce, and when this information is available, the dependence of friendship on distance is often modelled by pre-specified parametric functions or derived from theory without further empirical assessment. This paper aims to give a detailed representation of the association between distance and the likelihood of friendship existence and friendship dynamics, and how this is modified by a few basic social and individual factors. The data employed is a three-wave network of 336 adolescents living in a small Swedish town, for whom information has been collected on their household locations. The analysis is a three-step process that combines 1) nonparametric logistic regressions to unravel the overall functional form of the dependence of friendship on distance, without assuming it has a particular strength or shape; 2) parametric logistic regressions to construct suitable transformations of distance that can be employed in 3) stochastic models for longitudinal network data, to assess how distance, individual covariates, and network structure shape adolescent friendship dynamics. It was found that the log-odds of friendship existence and friendship dynamics decrease smoothly with the logarithm of distance. For adolescents in different schools the dependence is linear, and stronger than for adolescents in the same school. Living nearby accounts, in this dataset, for an aspect of friendship dynamics that is not explicitly modelled by network structure or by individual covariates. In particular, the estimated distance effect is not correlated with reciprocity or transitivity effects.

Assessing and accounting for time heterogeneity in stochastic actor oriented models.

This paper explores time heterogeneity in stochastic actor oriented models (SAOM) proposed by Snijders (Sociological Methodology. Blackwell, Boston, pp 361-395, 2001) which are meant to study the evolution of networks. SAOMs model social networks as directed graphs with nodes representing people, organizations, etc., and dichotomous relations representing underlying relationships of friendship, advice, etc. We illustrate several reasons why heterogeneity should be statistically tested and provide a fast, convenient method for assessment and model correction. SAOMs provide a flexible framework for network dynamics which allow a researcher to test selection, influence, behavioral, and structural properties in network data over time. We show how the forward-selecting, score type test proposed by Schweinberger (Chapter 4: Statistical modeling of network panel data: goodness of fit. PhD thesis, University of Groningen 2007) can be employed to quickly assess heterogeneity at almost no additional computational cost. One step estimates are used to assess the magnitude of the heterogeneity. Simulation studies are conducted to support the validity of this approach. The ASSIST dataset (Campbell et al. Lancet 371(9624):1595-1602, 2008) is reanalyzed with the score type test, one step estimators, and a full estimation for illustration. These tools are implemented in the RSiena package, and a brief walkthrough is provided.

Why Are Some More Peer Than Others? Evidence from a Longitudinal Study of Social Networks and Individual Academic Performance.

Studies of peer effects in educational settings confront two main problems. The first is the presence of endogenous sorting which confounds the effects of social influence and social selection on individual attainment. The second is how to account for the local network dependencies through which peer effects influence individual behavior. We empirically address these problems using longitudinal data on academic performance, friendship, and advice seeking relations among students in a full-time graduate academic program. We specify stochastic agent-based models that permit estimation of the interdependent contribution of social selection and social influence to individual performance. We report evidence of peer effects. Students tend to assimilate the average performance of their friends and of their advisors. At the same time, students attaining similar levels of academic performance are more likely to develop friendship and advice ties. Together, these results imply that processes of social influence and social selection are sub-components of a more general a co-evolutionary process linking network structure and individual behavior. We discuss possible points of contact between our findings and current research in the economics and sociology of education.

Smoking-based selection and influence in gender-segregated friendship networks: a social network analysis of adolescent smoking.

AIMS: The main goal of this study was to examine differences between adolescent male and female friendship networks regarding smoking-based selection and influence processes using newly developed social network analysis methods that allow the current state of continuously changing friendship networks to act as a dynamic constraint for changes in smoking behaviour, while allowing current smoking behaviour to be simultaneously a dynamic constraint for changes in friendship networks. DESIGN: Longitudinal design with four measurements. SETTING: Nine junior high schools in Finland. PARTICIPANTS: A total of 1163 adolescents (mean age = 13.6 years) who participated in the control group of the ESFA (European Smoking prevention Framework Approach) study, including 605 males and 558 females. MEASUREMENTS: Smoking behaviour of adolescents, parents, siblings and friendship ties. FINDINGS: Smoking-based selection of friends was found in male as well as female networks. However, support for influence among friends was found only in female networks. Furthermore, females and males were both influenced by parental smoking behaviour. CONCLUSIONS: In Finnish adolescents, both male and female smokers tend to select other smokers as friends but it appears that only females are influenced to smoke by their peer group. This suggests that prevention campaigns targeting resisting peer pressure may be more effective in adolescent girls than boys.