Deviant Communities in Social Media

The structure of a social network is fundamentally related to the interests of its members. People assort spontaneously based on the topics that are relevant to them, forming social groups that revolve around different subjects. Online social media are also favorable ecosystems for the formation of topical communities centered on matters that are not commonly taken up by the general public because of the embarrassment, discomfort, or shock they may cause.

Those are communities that depict or discuss what are usually referred to as deviant behaviors, conducts that are commonly considered inappropriate because they are somehow violative of society's norms or moral standards that are shared among the majority of the members of society. Adult content consumption, drug use, excessive drinking, illegal hunting, eating disorders, or any self-harming or addictive practice are all examples of deviant behaviors. Many of them are represented, to different extents, on social media. However, since all these topics touch upon different societal taboos, the common-sense assumption is that they are embodied either in niche, isolated social groups or in communities that might be quite numerous but whose activity runs separately from the mainstream social media life. In line with this belief, also research has mostly considered those groups in isolation, focusing predominantly on the patterns of communications among community members or, from a sociological perspective, on the motivations of their members and on the impact of the group activities on their lives and perceptions.

In reality, people who are involved in deviant practices are not segregated outcasts, but are part of the fabric of the global society. As such, they can be members of multiple communities and interact with very diverse sets of people, possibly exposing their deviant behavior to the public. We aim to go beyond previous studies that looked at deviant groups in isolation by observing them in context.


We focus on the deviant behavior of adult content consumption. We study this phenomenon on a large anonymized dataset sampled from the Tumblr social network. The Tumblr dataset contains more than 130 million users and almost 7 billion directed dyadic interactions. We model the social network as a graph whose nodes are the users and whose edges are the observed interactions among them: users can follow (i.e., subscribe to the content produced by) other users or reblog (i.e., share) content generated by other users.

Content is produced by a small core of nodes clustered in dense sub-communities, but it is spread through bridge communities to the remainder of the network potentially reaching half of the users.

The network of users that exclusively produce explicit adult content is a tiny portion of the whole graph, representing less than 0.05% of Tumblr users in our sample. This tightly connected community of content producers is linked with the rest of the network with a very high number of (mostly incoming) ties. The Figure above shows the content spreading mechanism in the Tumblr network. We found two interesting communities that post less explicit adult content and more sporadically. They either focus on celebrities or function as aggregator blogs with high content variety. In both cases, they act as bridges allowing content generated within the producers communities to spread across the rest of the social network. If we consider as unintentionally exposed those users who follow other users who reblog deviant content, the fraction of users potentially exposed to adult content is as large as 50% of the Tumblr sample.

Content diffusion involves users, young and underage, both male and female.

Consumption and production of adult content in a general purpose online social networks have never been studied at this scale before. It is known that male users consume more adult content than female, but if we analyze the consumption according to age we observe interesting surprisingly patterns. The consumption of adult content is substantially equal between the two genders under 25 years old. After that age the percentage of male users increases progressively compared to the female users. We thus confirm then that male users consume more adult content, but surprisingly we found that in youth consumption is comparable among the two genders. Finally, we found that, in order to limit the potential exposition of underage users, it would be sufficient to restrict the content production of just 200 users of network.

Contact: Mauro Coletto

Mauro Coletto (IMT Lucca & ISTI-CNR Pisa), Luca Maria Aiello (Bell Labs, UK), Claudio Lucchese, Fabrizio Silvestri (ISTI-CNR Pisa)
Referece: Coletto, M., Aiello, L. M., Lucchese, C., Silvestri, F. (2016) On the Behaviour of Deviant Communities in Online Social Networks. In 10th International AAAI Conference on Web and Social Media. ICWSM 2016, May 17-20, Cologne, Germany