167 research outputs found
A Stochastic Model for the Species Abundance Problem in an Ecological Community
We propose a model based on coupled multiplicative stochastic processes to
understand the dynamics of competing species in an ecosystem. This process can
be conveniently described by a Fokker-Planck equation. We provide an analytical
expression for the marginalized stationary distribution. Our solution is found
in excellent agreement with numerical simulations and compares rather well with
observational data from tropical forests.Comment: 4 pages, 3 figures, submitted to PR
Traveling Trends: Social Butterflies or Frequent Fliers?
Trending topics are the online conversations that grab collective attention
on social media. They are continually changing and often reflect exogenous
events that happen in the real world. Trends are localized in space and time as
they are driven by activity in specific geographic areas that act as sources of
traffic and information flow. Taken independently, trends and geography have
been discussed in recent literature on online social media; although, so far,
little has been done to characterize the relation between trends and geography.
Here we investigate more than eleven thousand topics that trended on Twitter in
63 main US locations during a period of 50 days in 2013. This data allows us to
study the origins and pathways of trends, how they compete for popularity at
the local level to emerge as winners at the country level, and what dynamics
underlie their production and consumption in different geographic areas. We
identify two main classes of trending topics: those that surface locally,
coinciding with three different geographic clusters (East coast, Midwest and
Southwest); and those that emerge globally from several metropolitan areas,
coinciding with the major air traffic hubs of the country. These hubs act as
trendsetters, generating topics that eventually trend at the country level, and
driving the conversation across the country. This poses an intriguing
conjecture, drawing a parallel between the spread of information and diseases:
Do trends travel faster by airplane than over the Internet?Comment: Proceedings of the first ACM conference on Online social networks,
pp. 213-222, 201
Quantifying Biases in Online Information Exposure
Our consumption of online information is mediated by filtering, ranking, and
recommendation algorithms that introduce unintentional biases as they attempt
to deliver relevant and engaging content. It has been suggested that our
reliance on online technologies such as search engines and social media may
limit exposure to diverse points of view and make us vulnerable to manipulation
by disinformation. In this paper, we mine a massive dataset of Web traffic to
quantify two kinds of bias: (i) homogeneity bias, which is the tendency to
consume content from a narrow set of information sources, and (ii) popularity
bias, which is the selective exposure to content from top sites. Our analysis
reveals different bias levels across several widely used Web platforms. Search
exposes users to a diverse set of sources, while social media traffic tends to
exhibit high popularity and homogeneity bias. When we focus our analysis on
traffic to news sites, we find higher levels of popularity bias, with smaller
differences across applications. Overall, our results quantify the extent to
which our choices of online systems confine us inside "social bubbles."Comment: 25 pages, 10 figures, to appear in the Journal of the Association for
Information Science and Technology (JASIST
How algorithmic popularity bias hinders or promotes quality
Algorithms that favor popular items are used to help us select among many
choices, from engaging articles on a social media news feed to songs and books
that others have purchased, and from top-raked search engine results to
highly-cited scientific papers. The goal of these algorithms is to identify
high-quality items such as reliable news, beautiful movies, prestigious
information sources, and important discoveries --- in short, high-quality
content should rank at the top. Prior work has shown that choosing what is
popular may amplify random fluctuations and ultimately lead to sub-optimal
rankings. Nonetheless, it is often assumed that recommending what is popular
will help high-quality content "bubble up" in practice. Here we identify the
conditions in which popularity may be a viable proxy for quality content by
studying a simple model of cultural market endowed with an intrinsic notion of
quality. A parameter representing the cognitive cost of exploration controls
the critical trade-off between quality and popularity. We find a regime of
intermediate exploration cost where an optimal balance exists, such that
choosing what is popular actually promotes high-quality items to the top.
Outside of these limits, however, popularity bias is more likely to hinder
quality. These findings clarify the effects of algorithmic popularity bias on
quality outcomes, and may inform the design of more principled mechanisms for
techno-social cultural markets
Finding Streams in Knowledge Graphs to Support Fact Checking
The volume and velocity of information that gets generated online limits
current journalistic practices to fact-check claims at the same rate.
Computational approaches for fact checking may be the key to help mitigate the
risks of massive misinformation spread. Such approaches can be designed to not
only be scalable and effective at assessing veracity of dubious claims, but
also to boost a human fact checker's productivity by surfacing relevant facts
and patterns to aid their analysis. To this end, we present a novel,
unsupervised network-flow based approach to determine the truthfulness of a
statement of fact expressed in the form of a (subject, predicate, object)
triple. We view a knowledge graph of background information about real-world
entities as a flow network, and knowledge as a fluid, abstract commodity. We
show that computational fact checking of such a triple then amounts to finding
a "knowledge stream" that emanates from the subject node and flows toward the
object node through paths connecting them. Evaluation on a range of real-world
and hand-crafted datasets of facts related to entertainment, business, sports,
geography and more reveals that this network-flow model can be very effective
in discerning true statements from false ones, outperforming existing
algorithms on many test cases. Moreover, the model is expressive in its ability
to automatically discover several useful path patterns and surface relevant
facts that may help a human fact checker corroborate or refute a claim.Comment: Extended version of the paper in proceedings of ICDM 201
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