Blog 8: Density and Friendship Development

Aggression is not a common trait that we seek in a friendship.  However, research suggests that aggressive children are still known to have friends.  In their article “Forms and Functions of Aggression in Adolescent Friendship Selection and Influence: A Longitudinal Social Network Analysis,” Sijtsema and colleagues (2010) investigate the impacts of aggression on adolescent friendship.  Through this work they seek to explore:

1. The development of friendship networks in adolescence

2. How friendship selection may be predicted by aggression?

To explore these questions, they collected survey data from 6th – 9th grade students over the course of 3 years.  Students were asked to nominate up to 18 friends in their grade at school as well as provide information on the length of their friendship.  During this data collection, they also collected a self-report survey about the students aggression.  The sample population for this study is a longitudinal sample of adolescents in middle school in a medium-sized urban community in the North East.  The sample was comprised of 65% White students, 17% Black students, 6% Latinx students  and 13% students of other race/ ethnicities.  About half of the sample identified as females and all participants were between the ages of 12 and 14. 

In this analysis, the students were used as the nodes, and the friendships between them were the links, whether one-sided or reciprocated.  The density metric was investigated to understand  the first research question about how friendship networks develop over middle school.  Density was defined as depicted in Figure 1, and as much could increase or decrease over time.  

Figure 1. Defining Density

By and large, Sijtsema and colleagues  found that the density of the network decreased over time, suggesting that students made fewer nominations of friends as they progressed through middle school.  Figure 2 demonstrates how this phenomenon occurred across 7 of the 8 different networks.  From this finding, they concluded that “adolescents were less inclined to just nominate classmates as friends. Instead they favored friendships that were mutual….” This contributed to the decrease in density of the network, but didnt necessarily suggest that adolescents had lost friendships between time point 1 and time point 3.

Figure 2. Density over time

In this way, the density metric provided us with an understanding of how the structure of the network as a whole changed over time.  This goes above and beyond what we could have learned from a nodal metric that only allows us to investigate how individual nodes function in a network.   Instead, structural metrics like this one inform us about the functioning of the friendship network as opposed to a few adolescents in the network.  

Sijtsema, J. J., Ojanen, T., Veenstra, R., Lindenberg, S., Hawley, P. H., & Little, T. D. (2010). Forms and functions of aggression in adolescent friendship selection and influence: A longitudinal social network analysis. Social Development19(3), 515-534.

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