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Concept: Mathematical sociology

41

Although we interact with a wide network of people on a daily basis, the social psychology literature has primarily focused on interactions with close friends and family. The present research tested whether subjective well-being is related not only to interactions with these strong ties but also to interactions with weak social ties (i.e., acquaintances). In Study 1, students experienced greater happiness and greater feelings of belonging on days when they interacted with more classmates than usual. Broadening the scope in Studies 2A and 2B to include all daily interactions (with both strong and weak ties), we again found that weak ties are related to social and emotional well-being. The current results highlight the power of weak ties, suggesting that even social interactions with the more peripheral members of our social networks contribute to our well-being.

Concepts: Interpersonal relationships, Psychology, Mathematical sociology, Human bonding, Interpersonal ties, Sociology

16

Homophily, the tendency of individuals to associate with others who share similar traits, has been identified as a major driving force in the formation and evolution of social ties. In many cases, it is not clear if homophily is the result of a socialization process, where individuals change their traits according to the dominance of that trait in their local social networks, or if it results from a selection process, in which individuals reshape their social networks so that their traits match those in the new environment. Here we demonstrate the detailed temporal formation of strong homophily in academic achievements of high school and university students. We analyze a unique dataset that contains information about the detailed time evolution of a friendship network of 6,000 students across 42 months. Combining the evolving social network data with the time series of the academic performance (GPA) of individual students, we show that academic homophily is a result of selection: students prefer to gradually reorganize their social networks according to their performance levels, rather than adapting their performance to the level of their local group. We find no signs for a pull effect, where a social environment of good performers motivates bad students to improve their performance. We are able to understand the underlying dynamics of grades and networks with a simple model. The lack of a social pull effect in classical educational settings could have important implications for the understanding of the observed persistence of segregation, inequality and social immobility in societies.

Concepts: Network science, Homophily, Social capital, Networks, Mathematical sociology, Network theory, Social network, Sociology

15

BackgroundConnectedness is a central dimension of personal recovery from severe mental illness (SMI). Research reports that people with SMI have lower social capital and poorer-quality social networks compared to the general population.AimsTo identify personal well-being network (PWN) types and explore additional insights from mapping connections to places and activities alongside social ties.MethodWe carried out 150 interviews with individuals with SMI and mapped social ties, places and activities and their impact on well-being. PWN types were developed using social network analysis and hierarchical k-means clustering of this data.ResultsThree PWN types were identified: formal and sparse; family and stable; and diverse and active. Well-being and social capital varied within and among types. Place and activity data indicated important contextual differences within social connections that were not found by mapping social networks alone.ConclusionsPlace locations and meaningful activities are important aspects of people’s social worlds. Mapped alongside social networks, PWNs have important implications for person-centred recovery approaches through providing a broader understanding of individual’s lives and resources.

Concepts: Networks, Social networks, Cultural economics, Mathematical sociology, Network theory, Social capital, Social network, Sociology

10

Information and behaviour can spread through interpersonal ties. By targeting influential individuals, health interventions that harness the distributive properties of social networks could be made more effective and efficient than those that do not. Our aim was to assess which targeting methods produce the greatest cascades or spillover effects and hence maximise population-level behaviour change.

Concepts: Network science, Social network, Mathematical sociology, Effectiveness, Networks, Network theory, Randomized controlled trial, Sociology

9

Use of online social networks for smoking cessation has been associated with abstinence. Little is known about the mechanisms through which the formation of social ties in an online network may influence smoking behavior. Using dynamic social network analysis, we investigated how temporal changes of an individual’s number of social network ties are prospectively related to abstinence in an online social network for cessation. In a network where quitting is normative and is the focus of communications among members, we predicted that an increasing number of ties would be positively associated with abstinence.

Concepts: Complex network, Mathematical sociology, Knowledge management, Network theory, Social network aggregation, Networks, Sociology, Social network

9

Individuals' centrality in their social network (who they and their social ties are connected to) has been associated with fertility, longevity, disease and information transmission in a range of taxa. Here, we present the first exploration in humans of the relationship between reproductive success and different measures of network centrality of 39 Agta and 38 BaYaka mothers. We collected three-meter contact (‘proximity’) networks and reproductive histories to test the prediction that individual centrality is positively associated with reproductive fitness (number of living offspring). Rather than direct social ties influencing reproductive success, mothers with greater indirect centrality (i.e. centrality determined by second and third degree ties) produced significantly more living offspring. However, indirect centrality is also correlated with sickness in the Agta, suggesting a trade-off. In complex social species, the optimisation of individuals' network position has important ramifications for fitness, potentially due to easy access to different parts of the network, facilitating cooperation and social influence in unpredictable ecologies.

Concepts: Complex network, Mathematical sociology, Network theory, Reproductive success, Centrality, Social network, Networks, Sociology

5

Social ties are crucial for humans. Disruption of ties through social exclusion has a marked effect on our thoughts and feelings; however, such effects can be tempered by broader social network resources. Here, we use fMRI data acquired from 80 male adolescents to investigate how social exclusion modulates functional connectivity within and across brain networks involved in social pain and understanding the mental states of others (i.e., mentalizing). Furthermore, using objectively logged friendship network data, we examine how individual variability in brain reactivity to social exclusion relates to the density of participants' friendship networks, an important aspect of social network structure. We find increased connectivity within a set of regions previously identified as a mentalizing system during exclusion relative to inclusion. These results are consistent across the regions of interest as well as a whole-brain analysis. Next, examining how social network characteristics are associated with task-based connectivity dynamics, we find that participants who showed greater changes in connectivity within the mentalizing system when socially excluded by peers had less dense friendship networks. This work provides insight to understand how distributed brain systems respond to social and emotional challenges and how such brain dynamics might vary based on broader social network characteristics.

Concepts: Network science, Social capital, Complex network, Mathematical sociology, Networks, Network theory, Social network, Sociology

2

The food industry is often described as having more power and influence in nutrition policymaking than nutrition professionals, scientists and other practitioners working for the public interest; yet authors often allude to this point as an assumed truth, rather than an evidence-based fact. This paper applies social network analysis techniques to provide a concise evidence-based demonstration of the food industry’s capacity to influence nutrition policymaking networks in Australia. Network analysis using four rounds of data collection was undertaken, and the capacity of individual actors and occupational categories to influence policy decision makers were analysed. Network graphs were developed using cluster analysis to identify the structure of clusters and the path distance of actors from decision makers. The assumed advantage for the ‘food industry’ was present both strategically in overall network position and with respect to the number of direct access points to ‘decision makers’, whereas ‘nutrition professionals’ were densely clustered together with limited links to key ‘decision makers’. The results demonstrate that the food industry holds the strategic high ground in advocating their interests to policymakers in the contexts studied. Nutrition professionals may be hampered by their reliance on strong ties with other nutrition professionals as well as limited direct links to ‘decision makers’.

Concepts: Food industry, Mathematical sociology, Food, Networks, Network theory, Policy, Sociology, Social network

2

Friend of a friend relationships, or the indirect connections between people, influence our health, well-being, financial success and reproductive output. As with humans, social behaviours in other animals often occur within a broad interconnected network of social ties. Yet studies of animal social behaviour tend to focus on associations between pairs of individuals. With the increase in popularity of social network analysis, researchers have started to look beyond the dyad to examine the role of indirect connections in animal societies. Here, I provide an overview of the new knowledge that has been uncovered by these studies. I focus on research that has addressed both the causes of social behaviours, i.e. the cognitive and genetic basis of indirect connections, as well as their consequences, i.e. the impact of indirect connections on social cohesion, information transfer, cultural practices and fitness. From these studies, it is apparent that indirect connections play an important role in animal behaviour, although future research is needed to clarify their contribution.

Concepts: Mathematical sociology, Social relation, Network theory, Knowledge management, Structural cohesion, Psychology, Social network, Sociology

2

A relationship between people’s mobility and their social networks is presented based on an analysis of calling and mobility traces for one year of anonymized call detail records of over one million mobile phone users in Portugal. We find that about 80% of places visited are within just 20 km of their nearest (geographical) social ties' locations. This figure rises to 90% at a ‘geo-social radius’ of 45 km. In terms of their travel scope, people are geographically closer to their weak ties than strong ties. Specifically, they are 15% more likely to be at some distance away from their weak ties than strong ties. The likelihood of being at some distance from social ties increases with the population density, and the rates of increase are higher for shorter geo-social radii. In addition, we find that area population density is indicative of geo-social radius where denser areas imply shorter radii. For example, in urban areas such as Lisbon and Porto, the geo-social radius is approximately 7 km and this increases to approximately 15 km for less densely populated areas such as Parades and Santa Maria da Feira.

Concepts: Geography, Mathematical sociology, Population ecology, Population, Mobile phone, Demography, Sociology, Population density