NoisyAnnot Causal News Corpus 2022 Causality Detection using Multiple Annotation Decisions Quynh Anh Nguyen1 2Arka Mitra2

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NoisyAnnot@ Causal News Corpus 2022: Causality Detection using
Multiple Annotation Decisions
Quynh Anh Nguyen1, 2 Arka Mitra2
1University of Milan 2ETH Zürich
quynguyen@ethz.ch, amitra@ethz.ch
Abstract
The paper describes the work that has been
submitted to the 5th workshop on Challenges
and Applications of Automated Extraction of
socio-political events from text (CASE 2022).
The work is associated with Subtask 1 of
Shared Task 3 that aims to detect causality in
protest news corpus. The authors used dif-
ferent large language models with customized
cross-entropy loss functions that exploit anno-
tation information. The experiments showed
that bert-based-uncased with refined cross-
entropy outperformed the others, achieving a
F1 score of 0.8501 on the Causal News Cor-
pus dataset.
1 Introduction
A causal relationship in a sentence implies an un-
derlying semantic dependency between the two
main clauses. The clauses in these sentences are
generally connected by markers which can have
different parts of tags in the sentence. Moreover,
the markers can be either implicit or explicit and
for these reasons, one cannot rely on regex or
dictionary-based systems. Thus, there is a need
to investigate the context of the sentences. For the
given task, we exploited different large language
models that provide a contextual representation of
sentences to tackle causality detection.
Shared task 3 in CASE-2022 (Tan et al.,2022a)
aims for causality detection in news corpus, which
can be structured as a text classification problem
with binary labels. Pre-trained transformer-based
models (Vaswani et al.,2017) have shown success
on tackling a wide range of NLP tasks including
text generation, text classification, etc. The authors
look into inter-annotation agreements and number
of experts and how they can be included in the
loss to improve the performance of the pre-trained
models.
The main contributions of the paper are as fol-
lows:
1.
Extensive experimentation with different large
language models.
2.
Incorporation of additional annotation infor-
mation, i.e inter-annotation agreement and the
number of annotators, to the loss.
The remaining paper is formulated as follows:
Section 2reviews the related work, section 3de-
scribes the dataset on which the work has been
done, section 4discusses the methodology used
in the paper, the following section discusses the
results and provides an ablation of the various loss
functions introduced and finally, section 6con-
cludes the paper and suggests future works.
2 Related Work
Multiple annotations on a single sample reduce
the chances of the labelling to be incorrect or bias
being incorporated into the dataset (Snow et al.,
2008). Including multiple annotators also leads
to disagreement among the labels that have been
provided by them. The final or gold annotation is
then usually determined by majority voting (Sabou
et al.,2014) or by using the label of an "expert"
(Waseem and Hovy,2016). There are also different
methodologies which do not use majority voting to
select the "ground truth".
Expectation Maximization algorithm has been
used to account for the annotator error (Dawid and
Skene,1979). Entropy metrics have been devel-
oped to identify the performance of the annota-
tors(Waterhouse,2012;Hovy et al.,2013;Gordon
et al.,2021). Multi-task learning is also used to deal
with disagreement in the labels (Fornaciari et al.,
2021;Liu et al.,2019;Cohn and Specia,2013;
Davani et al.,2022). There are methods which
include the annotation disagreement into the loss
function for part of speech tagging (Plank et al.,
2014;Prabhakaran et al.,2012) on SVMs and per-
ceptron model. The present work considers the
inter-annotator agreement as well as the number
arXiv:2210.14852v2 [cs.CL] 1 Dec 2022
of annotators into the loss function for any model.
The work also compares the performance when the
annotators who disagree with the majority voting
has been ignored.
3 Dataset
The Causal News Corpus dataset (Tan et al.,2022b)
consists of 3,559 event sentences extracted from
protest event news. Each sample in the dataset con-
tains the text, the corresponding label, the number
of experts who annotated the label and the degree
of agreement among the experts. Figure 1shows a
sample from the provided training set. The training
data is fairly balanced, containing 1603 sentences
with a causal structure and 1322 sentences without
a causal structure. Also, the number of causal and
non-causal sentences in the validation set does not
differ significantly. Finally, 311 news articles have
been used as test set for evaluation.
Figure 1: A datapoint from the provided training data.
Besides the binary labels, the Causal News Cor-
pus dataset also provides additional information
regarding the number of experts who labeled the
sentence and the percentage of agreement between
them. Figure 1shows that the number of experts
who annotated the text "The farmworkers’strike re-
sumed on Tuesday when their demands were not
met." is 3 (
num_votes = 3
). Also, all of the ex-
perts labeled the sentence to be causal so the agree-
ment is 1.0 (100% agreement) and the label is 1. In
case only one of three experts assigned label 1 to
the previous text, the three predictors
num_votes
,
agreement
,
label
would now become
3
,
2
3
,
0
respectively. In this paper, the authors exploit
this information to give the model more prior and
thus potentially improve the model’s performance,
which has been described in more detail in section
4.
4 Methodology
The section discusses the pipeline, the different
types of loss functions that were implemented, and
the experimental details that have been used in the
third shared task for CASE 2022 (Tan et al.,2022a).
4.1 Pipeline
The authors finetuned large language models with
different loss functions to tackle Subtask 1 in
Shared Task 3 of CASE@EMNLP-2022, causality
detection in a given sentence. The problem can be
reformulated as a binary classification where the
model predicts whether the sentence is causal or
not. Since contextual awareness plays an essential
role in handling this specific task, the authors used
several transformer-based models, namely, BERT
(Devlin et al.,2019), FinBERT (Liu et al.,2020),
XLNET (Yang et al.,2019) and RoBERTa (Zhuang
et al.,2021).
The given sentence is first tokenized by a tok-
enizer from the corresponding pretrained model
architecture provided by HuggingFace (Wolf et al.,
2020). The vector output from the tokenization
stage is then fed as input to the model. The most in-
formative token is the classification token ([CLS]),
which is a special token that can be used as a
sentence representation. The [CLS] token is then
passed through a feed-forward network to gener-
ate logits. The softmax over the logits gives us
the probability of whether the sentence is causal or
not. For each model, the authors experimented with
cross-entropy loss and proposed two loss functions
described in detail in subsection 4.2.
4.2 Loss Functions
Cross Entropy Loss
The loss of the classifica-
tion task can be represented by a simple cross-
entropy loss, as shown in Equation 1:
L=1
M
M
X
i=1
(ytrue
ilog(ypred
i)
(1 ytrue
i)log(1 ypred
i))
(1)
where
ytrue
i
and
ypred
i
denote the true label and the
predicted label for the
ith
input in a batch of M
sentences.
Noisy Cross Entropy Loss
The dataset not only
provides the standard information about
{text,
label}
, but also contains the information about
the number of experts who annotated the sentence’s
label, and proportion of agreement between them.
The authors have considered the annotation by
each of the experts to be the true label for the sen-
tence. For a sentence with
n
expert annotations
摘要:

NoisyAnnot@CausalNewsCorpus2022:CausalityDetectionusingMultipleAnnotationDecisionsQuynhAnhNguyen1,2ArkaMitra21UniversityofMilan2ETHZürichquynguyen@ethz.ch,amitra@ethz.chAbstractThepaperdescribestheworkthathasbeensubmittedtothe5thworkshoponChallengesandApplicationsofAutomatedExtractionofsocio-politic...

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