37 research outputs found
A Large-Scale Community Structure Analysis In Facebook
Understanding social dynamics that govern human phenomena, such as
communications and social relationships is a major problem in current
computational social sciences. In particular, given the unprecedented success
of online social networks (OSNs), in this paper we are concerned with the
analysis of aggregation patterns and social dynamics occurring among users of
the largest OSN as the date: Facebook. In detail, we discuss the mesoscopic
features of the community structure of this network, considering the
perspective of the communities, which has not yet been studied on such a large
scale. To this purpose, we acquired a sample of this network containing
millions of users and their social relationships; then, we unveiled the
communities representing the aggregation units among which users gather and
interact; finally, we analyzed the statistical features of such a network of
communities, discovering and characterizing some specific organization patterns
followed by individuals interacting in online social networks, that emerge
considering different sampling techniques and clustering methodologies. This
study provides some clues of the tendency of individuals to establish social
interactions in online social networks that eventually contribute to building a
well-connected social structure, and opens space for further social studies.Comment: 30 pages, 13 Figures - Published on: EPJ Data Science, 1:9, 2012 -
open access at: http://www.epjdatascience.com/content/1/1/
Using network science to analyze football passing networks: dynamics, space, time and the multilayer nature of the game
From the diversity of applications of Network Science, in this Opinion Paper
we are concerned about its potential to analyze one of the most extended group
sports: Football (soccer in U.S. terminology). As we will see, Network Science
allows addressing different aspects of the team organization and performance
not captured by classical analyses based on the performance of individual
players. The reason behind relies on the complex nature of the game, which,
paraphrasing the foundational paradigm of complexity sciences "can not be
analyzed by looking at its components (i.e., players) individually but, on the
contrary, considering the system as a whole" or, in the classical words of
after-match interviews "it's not just me, it's the team".Comment: 7 pages, 1 figur
On Facebook, most ties are weak
Pervasive socio-technical networks bring new conceptual and technological
challenges to developers and users alike. A central research theme is
evaluation of the intensity of relations linking users and how they facilitate
communication and the spread of information. These aspects of human
relationships have been studied extensively in the social sciences under the
framework of the "strength of weak ties" theory proposed by Mark Granovetter.13
Some research has considered whether that theory can be extended to online
social networks like Facebook, suggesting interaction data can be used to
predict the strength of ties. The approaches being used require handling
user-generated data that is often not publicly available due to privacy
concerns. Here, we propose an alternative definition of weak and strong ties
that requires knowledge of only the topology of the social network (such as who
is a friend of whom on Facebook), relying on the fact that online social
networks, or OSNs, tend to fragment into communities. We thus suggest
classifying as weak ties those edges linking individuals belonging to different
communities and strong ties as those connecting users in the same community. We
tested this definition on a large network representing part of the Facebook
social graph and studied how weak and strong ties affect the
information-diffusion process. Our findings suggest individuals in OSNs
self-organize to create well-connected communities, while weak ties yield
cohesion and optimize the coverage of information spread.Comment: Accepted version of the manuscript before ACM editorial work. Check
http://cacm.acm.org/magazines/2014/11/179820-on-facebook-most-ties-are-weak/
for the final versio
Quantifying the Effect of Sentiment on Information Diffusion in Social Media
Social media have become the main vehicle of information production and
consumption online. Millions of users every day log on their Facebook or
Twitter accounts to get updates and news, read about their topics of interest,
and become exposed to new opportunities and interactions. Although recent
studies suggest that the contents users produce will affect the emotions of
their readers, we still lack a rigorous understanding of the role and effects
of contents sentiment on the dynamics of information diffusion. This work aims
at quantifying the effect of sentiment on information diffusion, to understand:
(i) whether positive conversations spread faster and/or broader than negative
ones (or vice-versa); (ii) what kind of emotions are more typical of popular
conversations on social media; and, (iii) what type of sentiment is expressed
in conversations characterized by different temporal dynamics. Our findings
show that, at the level of contents, negative messages spread faster than
positive ones, but positive ones reach larger audiences, suggesting that people
are more inclined to share and favorite positive contents, the so-called
positive bias. As for the entire conversations, we highlight how different
temporal dynamics exhibit different sentiment patterns: for example, positive
sentiment builds up for highly-anticipated events, while unexpected events are
mainly characterized by negative sentiment. Our contribution is a milestone to
understand how the emotions expressed in short texts affect their spreading in
online social ecosystems, and may help to craft effective policies and
strategies for content generation and diffusion.Comment: 10 pages, 5 figure
Measuring Emotional Contagion in Social Media
Social media are used as main discussion channels by millions of individuals
every day. The content individuals produce in daily social-media-based
micro-communications, and the emotions therein expressed, may impact the
emotional states of others. A recent experiment performed on Facebook
hypothesized that emotions spread online, even in absence of non-verbal cues
typical of in-person interactions, and that individuals are more likely to
adopt positive or negative emotions if these are over-expressed in their social
network. Experiments of this type, however, raise ethical concerns, as they
require massive-scale content manipulation with unknown consequences for the
individuals therein involved. Here, we study the dynamics of emotional
contagion using Twitter. Rather than manipulating content, we devise a null
model that discounts some confounding factors (including the effect of
emotional contagion). We measure the emotional valence of content the users are
exposed to before posting their own tweets. We determine that on average a
negative post follows an over-exposure to 4.34% more negative content than
baseline, while positive posts occur after an average over-exposure to 4.50%
more positive contents. We highlight the presence of a linear relationship
between the average emotional valence of the stimuli users are exposed to, and
that of the responses they produce. We also identify two different classes of
individuals: highly and scarcely susceptible to emotional contagion. Highly
susceptible users are significantly less inclined to adopt negative emotions
than the scarcely susceptible ones, but equally likely to adopt positive
emotions. In general, the likelihood of adopting positive emotions is much
greater than that of negative emotions.Comment: 10 pages, 5 figure
Uncovering nodes that spread information between communities in social networks
From many datasets gathered in online social networks, well defined community
structures have been observed. A large number of users participate in these
networks and the size of the resulting graphs poses computational challenges.
There is a particular demand in identifying the nodes responsible for
information flow between communities; for example, in temporal Twitter networks
edges between communities play a key role in propagating spikes of activity
when the connectivity between communities is sparse and few edges exist between
different clusters of nodes. The new algorithm proposed here is aimed at
revealing these key connections by measuring a node's vicinity to nodes of
another community. We look at the nodes which have edges in more than one
community and the locality of nodes around them which influence the information
received and broadcasted to them. The method relies on independent random walks
of a chosen fixed number of steps, originating from nodes with edges in more
than one community. For the large networks that we have in mind, existing
measures such as betweenness centrality are difficult to compute, even with
recent methods that approximate the large number of operations required. We
therefore design an algorithm that scales up to the demand of current big data
requirements and has the ability to harness parallel processing capabilities.
The new algorithm is illustrated on synthetic data, where results can be judged
carefully, and also on a real, large scale Twitter activity data, where new
insights can be gained
Online Popularity and Topical Interests through the Lens of Instagram
Online socio-technical systems can be studied as proxy of the real world to
investigate human behavior and social interactions at scale. Here we focus on
Instagram, a media-sharing online platform whose popularity has been rising up
to gathering hundred millions users. Instagram exhibits a mixture of features
including social structure, social tagging and media sharing. The network of
social interactions among users models various dynamics including
follower/followee relations and users' communication by means of
posts/comments. Users can upload and tag media such as photos and pictures, and
they can "like" and comment each piece of information on the platform. In this
work we investigate three major aspects on our Instagram dataset: (i) the
structural characteristics of its network of heterogeneous interactions, to
unveil the emergence of self organization and topically-induced community
structure; (ii) the dynamics of content production and consumption, to
understand how global trends and popular users emerge; (iii) the behavior of
users labeling media with tags, to determine how they devote their attention
and to explore the variety of their topical interests. Our analysis provides
clues to understand human behavior dynamics on socio-technical systems,
specifically users and content popularity, the mechanisms of users'
interactions in online environments and how collective trends emerge from
individuals' topical interests.Comment: 11 pages, 11 figures, Proceedings of ACM Hypertext 201
Latent Space Model for Multi-Modal Social Data
With the emergence of social networking services, researchers enjoy the
increasing availability of large-scale heterogenous datasets capturing online
user interactions and behaviors. Traditional analysis of techno-social systems
data has focused mainly on describing either the dynamics of social
interactions, or the attributes and behaviors of the users. However,
overwhelming empirical evidence suggests that the two dimensions affect one
another, and therefore they should be jointly modeled and analyzed in a
multi-modal framework. The benefits of such an approach include the ability to
build better predictive models, leveraging social network information as well
as user behavioral signals. To this purpose, here we propose the Constrained
Latent Space Model (CLSM), a generalized framework that combines Mixed
Membership Stochastic Blockmodels (MMSB) and Latent Dirichlet Allocation (LDA)
incorporating a constraint that forces the latent space to concurrently
describe the multiple data modalities. We derive an efficient inference
algorithm based on Variational Expectation Maximization that has a
computational cost linear in the size of the network, thus making it feasible
to analyze massive social datasets. We validate the proposed framework on two
problems: prediction of social interactions from user attributes and behaviors,
and behavior prediction exploiting network information. We perform experiments
with a variety of multi-modal social systems, spanning location-based social
networks (Gowalla), social media services (Instagram, Orkut), e-commerce and
review sites (Amazon, Ciao), and finally citation networks (Cora). The results
indicate significant improvement in prediction accuracy over state of the art
methods, and demonstrate the flexibility of the proposed approach for
addressing a variety of different learning problems commonly occurring with
multi-modal social data.Comment: 12 pages, 7 figures, 2 table