1. In the last decades the development of new technologies and the possibility to be
always connected has contributed to change the way that people socialize. In
particular mobile phones have become a main part of our social life letting us to stay
in touch every moment with our social network.
In this field a lot of studies tried to research and model the social dynamics of
individuals. In particular a useful model to represent people’s sociality is given by
the Ego Network. An ego network can be represented as a graph in which the ego is
in the center and is surrounded by his alters, namely the people that he interacts
with. Every alter is connected to the ego by a weighted edge, where the weight
symbolizes the strength of the tie. Dunbar’s[1] studies has identified a 4­level
concentric structure of the Ego network in which the smallest level, the one that
contains the strongest ties, is usually formed by 3­5 people and is called ​grooming
network​.
The purpose of this work was to study people’s interactions through calls and SMS.
The analysis were conducted over an anonymized dataset from a big italian mobile
operator containing millions of records.
The first step of the work was to find a way to confront calls and SMS. In fact,
whereas a phone call contains a single interaction, sms are asynchronous and
multiple messages can form a single interaction.
In order to find a dimension in which we can confront calls and sms I have analyzed
the exchanges of sms between couples of users from the dataset. The results
showed that the sms’s interactions usually have a bursty behaviour, i.e they are
organized in short periods of intense activity followed by periods of reduced or null
activity. From analysis i have found that a good threshold to consider two or more
messages in burst is 10 minutes. This result are in line with the literature.
As a consequence I have decided to consider a burst of sms as a single interaction.
The second step was to analyze the percentage occupied by the ​grooming network
on the total of interactions in the ego network. As a result I found that in networks
made of 30 to 100 contacts this value is between 30% and 70% and that with the
growing of the size of the personal network this interactions are distributed more
homogeneously and the fraction occupied by the grooming network decreases.
The final step of the work was to design and develop an android Application called
Groome ​with the aim of giving an easy to use tool to visualize the state of our ​ego
network​.

2.
Screenshot of application