  Fake news are nowadays an issue of pressing concern, given their recent rise
as a potential threat to high-quality journalism and well-informed public
discourse. The Fake News Challenge (FNC-1) was organized in 2017 to encourage
the development of machine learning-based classification systems for stance
detection (i.e., for identifying whether a particular news article agrees,
disagrees, discusses, or is unrelated to a particular news headline), thus
helping in the detection and analysis of possible instances of fake news. This
article presents a new approach to tackle this stance detection problem, based
on the combination of string similarity features with a deep neural
architecture that leverages ideas previously advanced in the context of
learning efficient text representations, document classification, and natural
language inference. Specifically, we use bi-directional Recurrent Neural
Networks, together with max-pooling over the temporal/sequential dimension and
neural attention, for representing (i) the headline, (ii) the first two
sentences of the news article, and (iii) the entire news article. These
representations are then combined/compared, complemented with similarity
features inspired on other FNC-1 approaches, and passed to a final layer that
predicts the stance of the article towards the headline. We also explore the
use of external sources of information, specifically large datasets of sentence
pairs originally proposed for training and evaluating natural language
inference methods, in order to pre-train specific components of the neural
network architecture (e.g., the RNNs used for encoding sentences). The obtained
results attest to the effectiveness of the proposed ideas and show that our
model, particularly when considering pre-training and the combination of neural
representations together with similarity features, slightly outperforms the
previous state-of-the-art.
