Critical size of ego communication networks

TL;DR

This study analyzes directed Ego Communication Networks (ECNs) built from Call Detail Records, revealing a critical size around 150 where network properties change significantly, supporting the Social Brain Hypothesis across cultures.

Contribution

It identifies a critical ECN size affecting network properties and provides empirical evidence supporting Dunbar's Number and the Social Brain Hypothesis.

Findings

ECN size around 150 marks a threshold for emotional closeness decline

The proportion of strong ties decreases beyond the critical size

Results support the universality of Dunbar's Number and the Social Brain Hypothesis

Abstract

With the help of information and communication technologies, studies on the overall social networks have been extensively reported recently. However, investigations on the directed Ego Communication Networks (ECNs) remain insufficient, where an ECN stands for a sub network composed of a centralized individual and his/her direct contacts. In this paper, the directed ECNs are built on the Call Detail Records (CDRs), which cover more than 7 million people of a provincial capital city in China for half a year. Results show that there is a critical size for ECN at about 150, above which the average emotional closeness between ego and alters drops, the balanced relationship between ego and network collapses, and the proportion of strong ties decreases. This paper not only demonstrate the significance of ECN size in affecting its properties, but also shows accordance with the "Dunbar's Number". These results can be viewed as a cross-culture supportive evidence to the well-known Social Brain Hypothesis (SBH).