Measuring the robustness of network community structure using assortativity

• Published in: Animal behaviour Vol. 112; pp. 237 - 246
• Main Authors: Shizuka, Daizaburo, Farine, Damien R.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2016; Harcourt Brace Jovanovich Ltd; Academic Press
• Subjects: Animal behavior; birds; Bootstrap method; bootstrapping; community detection; Community structure; data collection; flock; golden-crowned sparrow; humans; modularity; Sampling; social network; social networks; thornbill; tit; social network; bootstrapping; flock; golden-crowned sparrow; modularity; thornbill; community detection; tit
• ISSN: 0003-3472; 1095-8282
• DOI: 10.1016/j.anbehav.2015.12.007

The existence of discrete social clusters, or ‘communities’, is a common feature of social networks in human and nonhuman animals. The level of such community structure in networks is typically measured using an index of modularity, Q. While modularity quantifies the degree to which individuals associate within versus between social communities and provides a useful measure of structure in the social network, it assumes that the network has been well sampled. However, animal social network data is typically subject to sampling errors. In particular, the associations among individuals are often not sampled equally, and animal social network studies are often based on a relatively small set of observations. Here, we extend an existing framework for bootstrapping network metrics to provide a method for assessing the robustness of community assignment in social networks using a metric we call community assortativity (rcom). We use simulations to demonstrate that modularity can reliably detect the transition from random to structured associations in networks that differ in size and number of communities, while community assortativity accurately measures the level of confidence based on the detectability of associations. We then demonstrate the use of these metrics using three publicly available data sets of avian social networks. We suggest that by explicitly addressing the known limitations in sampling animal social network, this approach will facilitate more rigorous analyses of population-level structural patterns across social systems. •Measuring community structure in networks requires assigning nodes to communities.•We propose a method to assess observation error in community assignments.•We use simulations and empirical data to validate our robustness index (rcom).•We detail the interplay between sample size, modularity and community assignments.•Our metric, rcom, could accompany modularity values in studies of network structure.