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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>UMUTeam at MeO endEs 2021: Ensemble Learning for O ensive Language Identi cation using Linguistic Features, Fine-grained Negation, and Transformers</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Facultad de Informatica</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Universidad de Murcia</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Campus de Espinardo</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Spain</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>joseantonio.garcia</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>valenciag@um.es</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Computer Science Department, SINAI, CEATIC, Universidad de Jaen</institution>
          ,
          <addr-line>23071</addr-line>
          ,
          <country country="ES">Spain</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>This paper presents the participation of the UMUTeam in the MeO endEs shared task at IberLEF 2021. This task involves the identi cation and categorisation of o ensiveness in Spanish comments from di erent social networks (YouTube, Instagram and Twitter), and Mexican Spanish tweets. Speci cally, four subtasks were proposed: the rst one on multi-class classi cation of o ensiveness types, the second one also concerning multi-class classi cation but with contextual information, the third one on a binary classi cation of texts as o ensives or non-o ensives, and the last one also regarding a binary classi cation but with metadata. Subtasks 1 and 2 focus on generic Spanish, and subtasks 3 and 4 on Mexican Spanish. We have participated in the four subtasks with the aim of promoting the automatic identi cation of o ensiveness in Spanish variants. Our proposal for solving these subtasks is based on the combination of linguistic features (including ne-grained negation features) and embeddings using transformers and ensemble learning. We ranked in second place in subtask 1 with a micro-averaged F1-score of 87.8289%, rst in subtask 2 with a micro-averaged F1-score of 87.8289%, fth in subtask 3 with a macro-averaged F1-score of 67.0588%, and rst in subtask 4 with a macro-averaged F1-score of 66.9449%.</p>
      </abstract>
      <kwd-group>
        <kwd>O ensiveness</kwd>
        <kwd>Feature Engineering</kwd>
        <kwd>Negation processing</kwd>
        <kwd>Transformers</kwd>
        <kwd>Ensemble learning</kwd>
        <kwd>Natural Language Processing</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>Introduction</title>
      <p>This work describes the participation of the UMUTeam in the shared task
MeO endEs 2021 [22], organised in the IberLEF 2021 workshop [21] and aimed at
the identi cation of o ensive language and its categories. A text is considered
o ensive if it contains hurtful, derogatory or obscene comments made by one
person to another person [25]. The use of o ensive language in social media has
increased in recent years. Some users make use of the freedom of expression
o ered by these media to communicate in an o ensive way. This poses a
major problem for society as o ensive comments can cause signi cant harm to the
people they are directed at, such as depression or suicide.</p>
      <p>The aim of MeO endEs 2021 is to promote the development of tools to
detect and recognise o ensive language and its categories in Spanish and Mexican
Spanish. Speci cally, they are proposed four subtasks:
{ Subtask 1: Non-contextual multiclass classi cation for generic Spanish.
Identify the type of o ensiveness used in each of the given comment: non-o ensive
(NO), non-o ensive but with inadequate language (NOM), o ensive and
target is a person (OFP) or, o ensive and target is a group of people or collective
(OFG).
{ Subtask 2: Contextual multiclass classi cation for generic Spanish. Use
metadata as an additional source of information to identify the type of o
ensiveness: NO, NOM, OFP or OFG.
{ Subtask 3: Non-contextual binary classi cation for Mexican Spanish. Classify
each of the given tweet as o ensive or non-o ensive.
{ Subtask 4: Contextual binary classi cation for Mexican Spanish. Use
metadata as an additional source of information to classify each tweet as o ensive
or non-o ensive.</p>
      <p>The remainder of this manuscript is organised as follow. First, in Section 2,
a short overview on workshops regarding o ensiveness and Spanish corpora is
presented. Next, in Section 3, we give some insights regarding the datasets that
were made available to the participants. Following, in Section 4, the methodology
of our proposal is described. In Section 5, we show the results achieved by our
team and compare them with those obtained by the rest of participants. Finally,
the conclusions and future research directions are shown in Section 6.
2</p>
    </sec>
    <sec id="sec-2">
      <title>Background information</title>
      <p>
        O ensive language detection is a task of recent interest due to the proliferation
of this type of language in social media. One of the strategies used to stop
messages with o ensive content is to report these messages, but doing this manually
is not feasible due to the large amount of information that is published daily on
the Web. Therefore, research e orts are being invested to automate this process.
Studies on o ensive language have focused on hate speech [
        <xref ref-type="bibr" rid="ref5">18, 5</xref>
        ], cyberbulling
[
        <xref ref-type="bibr" rid="ref2 ref6">6, 2</xref>
        ] and aggression [16]. In fact, we can nd a large set of shared tasks about
this topic, such as the 2018 and 2019 editions of the GermEval Shared Task on
the Identi cation of O ensive Language [25, 24], the 2019 and 2020 editions of
the O ensEval shared task on Identifying and Categorising O ensive Language
in Social Media [26, 27], the AMI shared task on Automatic Misogyny Identi
cation at IberEval 2018 [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] and Evalita 2018 [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ], the 2019 and 2020 editions of
the HASOC track on Hate Speech and O ensive Content Identi cation [20, 19],
the HatEval shared task on the Detection of Hate Speech against Immigrants
and Women [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ], the MEX-A3T track at IberLEF 2019 on Authorship and
Aggressiveness Analysis [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ], and the 2018 and 2020 editions of the TRAC shared
task on Trolling, Aggression and Cyberbullying [15, 17].
      </p>
      <p>Of the tasks previously mentioned only AMI and HatEval provided datasets
on generic Spanish and MEX-A3T on Spanish Mexican, which are the languages
under studied in the MeO endEs task. On the one hand, the two AMI datasets
consist of documents written in English, Spanish and Italian and are annotated
according to three levels: misogyny (misogyny or not misogyny), misogynistic
category (discredit, derailing, dominance, sexual harassment and threats of
violence, and stereotype and objecti cation) and target (individuals or groups). In
the AMI shared task of IberEval and Evalita, two tasks were proposed: a binary
classi cation on misogyny identi cation and a categorisation of misogynistic
behaviours and targets. On the other hand, the HatEval dataset is composed of
tweets written in Spanish and English related to hate-speech towards women and
immigrants. Similar to AMI, two tasks were proposed in HatEval: a binary hate
speech detection against immigrants and women, and an aggressive behaviour
and target classi cation in which the participants were encouraged to discern
between aggressive or not aggressive messages, to later identify if the victim of
the harassment is a person or a collective. Finally, MEX-A3T proposed a binary
aggressiveness detection track focused on identifying aggressive tweets written in
Mexican Spanish. The MEX-A3T dataset was compiled from Mexico City and
contains documents with o ensive, vulgar, and aggressive language.
3</p>
    </sec>
    <sec id="sec-3">
      <title>Datasets</title>
      <p>Subtask 1 and subtask 2 are multi-classi cation, in which documents were tagged
as non-o ensive (NO), non-o ensive but with inadequate language (NOM), and
o ensive, discerning whether the target is a person (OFP) or a group (OFG).
According to the description provided by the organisers, the dataset was
compiled from multiple social networks, including YouTube, Instagram and Twitter.
The dataset was provided to the participants in two sets, depending on whether
the documents were labelled by three or ten annotators. It is worth mentioning
that the organisers of the task divided the corpus into three splits, namely, train,
development, and test. However, the o cial development set consisted only in
100 examples and, therefore, as the labels were not balanced, some classes get
under represented. Therefore, we decided to merge train and dev, and generate
two custom splits into a partition of 80-20. The original splits can be downloaded
at https://github.com/pendrag/MeO endEs. The dataset distribution for
subtasks 1 and 2 are depicted on Table 1, in which we can observe that the label
OFG is the one with fewer instances.</p>
      <p>In case of generic Spanish, in subtask 2, some contextual information were
provided along with the dataset, regarding the author of the document. This
metadata includes information about the social media in which the comment
was posted, the name of the channel or the main user involved (also known as
the in uencer), and its gender.</p>
      <p>For subtasks 3 and 4, concerning Spanish Mexican, the dataset consisted into
documents labelled as o ensive or non-o ensive. According to the organisers,
this dataset was compiled from Twitter and labelled at rst place as: o ensive,
aggressive, and vulgar but non o ensive, but nally merged as binary class. The
distribution of the labels across the di erent split is shown in Table 2. We can
observe that the relation among non-o ensive and o ensive documents is near
2.6 which can be considered a strong imbalance.</p>
      <p>For subtask 4, the organisers provided a large variety of contextual data
including the date of publication, its number of retweets, the number of times
the tweet has been marked as liked by users, and whether the tweet is a reply
or an original comment, among other contextual features.
4</p>
    </sec>
    <sec id="sec-4">
      <title>Methodology</title>
      <p>
        To accomplish all subtasks, our proposal is grounded on the combination of
different feature sets by means of ensembles. Particularly, we focus on two types of
features sets. On the one hand, we employ linguistic and interpretable features,
compiled by UMUTextStats (LF) [
        <xref ref-type="bibr" rid="ref9">9, 10</xref>
        ] and negation features (NE) [11{14]. On
the other hand, we study di erent types of embeddings from word embeddings
(WE) and sentence embeddings compiled from fastText (SE), to contextualised
word embeddings from Spanish BERT (BE), also known as BETO, and compiled
by ne-tuning the Spanish version of BERT (BF) [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ], extracting the embeddings
from the [CLS] token and applying a mean pooling, as suggested in [23].
Moreover, for subtasks 2 and 4 we compile contextual features (CF) from the datasets
provided.
      </p>
      <p>Regarding the linguistic features, the UMUTextStats tool is capable to
categorise a total of 365 features regarding semantics, pragmatics, lexical process,
social media, gurative language, or correction and style, among others.
Concerning the negation features we extract the list of negation cues appearing in
each text (simple cues (e.g., \no"/ not ), continuous cues (e.g. \en mi vida"/
in my life) and discontinuous cues (e.g. \ni...ni"/ nor...nor ) and compute their
total. With regard to the contextual features (CF), as commented during corpus
analysis (see Section 3), the datasets were very di erent regarding complexity
and number of features. For the generic Spanish dataset we encode the features
regarding media and gender with one-hot encoding. In case of Mexican
Spanish, we keep the features provided by the organisers of the task but we include
extra features from the date of the posts, to know whether a tweet was posted
during weekend or working day, and we divide the day into several time slots to
distinguish the tweets written in the morning, afternoon, evening and night.</p>
      <p>
        For all feature sets we carry out a process of preprocessing and normalisation
of the features. First, for the linguistic features we scale each feature
independently in a range [
        <xref ref-type="bibr" rid="ref1">0, 1</xref>
        ] with a MinMax scaler. For the negation features, however,
we apply a Robust Scaler as we found heavy outliers regarding one of the tweets
composed by repeating a negation multiple times. The same technique (Robust
Scaler) is applied to the contextual features, regardless the subtask. Next, we
apply a feature selection technique based on Mutual Information. According to
our evaluation with the development set, we keep this feature selection over LF,
SE and BE but keeping all the features for BF, WE, NE and CF as we achieved
better results without feature selection for those feature sets.
      </p>
      <p>To combine the features we evaluate di erent forms of ensembles of the best
model per feature set. Speci cally, we evaluate three types of ensembles: (1)
based on majority voting (mode), (2) based on a modi ed version of the majority
voting ensemble, weighting each vote with the weighted F1-score achieved on the
validation set, and (3) training a logistic regression model from the predictions
of each neural network model.</p>
      <p>Prior to our participation we evaluated di erent neural networks models and
traditional machine learning models in order to get some insights for the
reliability of each feature set used in combination or separately, as well as which
hyper-parameters of the networks worked well for each subtask. We, therefore,
performed an hyperparameter optimisation stage evaluating 110 neural network
per feature set in isolation and in combination, both for generic Spanish
(subtasks 1 and 2) and for Mexican Spanish (subtasks 3 and 4). We ranked each
model based on the micro-averaged F1-score (we used this measure because in
CodaLab the organisers indicated that submission would be evaluated with it,
but nally for subtasks 3 and 4 they used macro-averaged F1-score). The feature
sets evaluated during this stage were LF, NE, SE, BE, BF, and CF. During this
stage we also evaluated convolutional and recurrent neural networks with WE
from Spanish pre-trained word embeddings from fastText, gloVe, and word2vec.</p>
      <p>For each neural network tested during the hyperparameter optimisation we
evaluated di erent depths and di erent number of neurons (8, 16, 48, 64, 128,
256). The layers and the neurons were organised in shapes, including funnel,
rhombus, long funnel, brick, diamond, and triangle. It is worth noting that the
best results were achieved by simple models in the majority of cases, with one
or two layers and few neurons per layer. The majority of architectures evaluated
were Multilayer perceptrons because we rely on sentence xed embeddings and
linguistic features, thus, spatial and temporal data cannot be exploded.
However, in case of WE, we also evaluated Convolutional Neural Networks (CNN),
Bidirectional Long Short Term Memory (BiLSTM) and Bidirectional Gated
Recurrent Unit (BiGRU). In addition, we tried di erent dropout rates to avoid
over tting (0, 0.1, 0.2, and 0.3) and several activation functions including relu,
sigmoid, tanh, selu, and elu. We also included an early stopping mechanism and
a learning rate scheduler.</p>
      <p>Table 3 depicts the best parameters for each feature set for the generic
Spanish and Mexican Spanish datasets. We can observe that the best results were
achieved with multi-layer perceptrons, even for the WE, and with shallow
neural networks with one or two hidden layers. Deep neural networks achieved the
best result for NE in both datasets, with 5 and 7 hidden layers respectively, and
WE, both with 6 hidden layers. CF required a very simpler network for generic
Spanish but a complex one for Mexican Spanish. This fact can be explained due
to the simplicity of the CF for generic Spanish, including only the gender and
media type of the documents. It draws attention, when comparing generic and
Mexican Spanish, that the models for generic Spanish are generally simpler than
those for Mexican Spanish, despite having more instances and being multiclass.
5</p>
    </sec>
    <sec id="sec-5">
      <title>Results</title>
      <p>This section is divided into the two main subtasks regarding o ensive content
detection in generic Spanish (see Subsection 5.1) and Mexican Spanish (see
Subsection 5.2).
5.1</p>
      <p>Subtasks 1 and 2. Non-contextual and contextual multiclass
classi cation for generic Spanish
Subtask 1 and subtask 2 were evaluated by the following metrics: micro-averaged,
macro-averaged and weighted-averaged versions of precision (P), recall (R) and
F1-score (F1), and Mean Squared Error (MSE). The measure selected by the
organisers for ranking the systems was the micro-averaged F1-score.</p>
      <p>Each team could participate with up to three submissions and select the
best of them as o cial result. Table 4 contains the results of each of our runs
for subtask 1, non-contextual multiclass classi cation for generic Spanish. The
rst run consists of an ensemble of neural networks models trained with BE,
LF, NE, SE, and BF. The ensemble was built using a logistic regression from
the individual probabilities of each model. The second run, which is our o cial
result, consists of the same type of ensemble but only with BF, SE, and BE;
that is, by removing the linguistic features. We can observe than in this case,
we achieved slightly better micro-averaged F1-score but worse macro-averaged
precision and F1-score, which suggest that the usage of linguistic features are
bene cial for the classes NOM, OFG, and OFP. The third run consists of another
type of ensemble, based on the weighted mode of the individual predictions of
each model. The weights for this model were calculated based on the weighted
F1-score achieved with our custom validation set. We can observe than this run
achieved worst results than the ensembles based on logistic regression except for
MSE.</p>
      <p>As it has been previously mentioned, we selected our second run to participate
in subtask 1.The o cial leader board is depicted in Table 5. We reached the
second best result with a micro-averaged F1-score of 87.8289%. with a di erence
of 0.3307% with the best result, achieved by saroyehun (88.1596% of
microaveraged F1-score), and followed by xjywing (87.3291% of micro-averaged
F1score) with a di erence of 0.4998%. Due to the high number of non-o ensive
instances, the results of the micro-averaged F1-score among all participants is
similar. By looking the macro-averaged F1-score, we can observe that Marta NG BD
and Timen achieved lower results, which can indicate that some minority labels
were not classi ed. This subtask also includes a regression metric based on the
probabilities assigned for each class, that is measured using the Mean Squared
Error (MSE). As it can be observed, we got an MSE of 0.41134 and the results
achieved by the rest of the participants (lower is better) matches with the o cial
rank.</p>
      <p>Regarding substask 2, contextual multiclass classi cation for generic
Spanish, we employed the same techniques than for subtask 1. Table 6 contains the
results of our three runs. The results for the rst run, which consisted of the
ensemble based on logistic regression over BE, LF, NE, SE, and BF but including
contextual features (CF) in the ensemble, improves the micro-averaged F1-score
achieved in subtask 1 in 0.0294%. This behaviour was expected as the contextual
features of Spanish were few. However, the results improve the macro-averaged
metrics, which indicates that the contextual features contribute to the texts with
o ensive or vulgar content. For the second run, however, we evaluate a di erent
approach from subtask 1. We retrain the model including the validation set but
the results were not good. Specially, we can observe a signi cant drop in the
macro-averaged recall. Finally, for the third run we adopted a similar approach
for the second run of the rst subtask (see Table 4) removing the linguistic
features but keeping the ensemble model based on logistic regression from the
training dataset. As it can be observed, this run achieves worst micro-averaged
F1-score and macro-averaged precision, recall and F1-score. In this case, the rst
run is the one we selected for the o cial leader board of subtask 2. As it can
be observed from Table 7, only two participants sent runs and we achieved the
rst position in this subtask with a micro-average F1-score of 87.8289%.</p>
      <p>Figure 1 contains the ten top-ranked linguistic features according to mutual
information. We can observe that general and negative psycho-linguistic
processes are strong features to discern among non-o ensive documents with the
rest of the classes. However, they are not indicators to discern among o
ensive (OFP, OFG) or vulgar language (NOM). We also found informal speech
and swear language are the strongest correlation with the label NOM. O ensive
speech is also a strong marker related to when the o ensive message is towards
a person (OFP) and when the usage of the language is vulgar or not adequate
(NOM). As it can be observed, the number of words have greater in uence on
NO and OFG classes. We can nd a correlation of this feature with the number
of syllables, the overall length of the documents and readability scores.
5.2</p>
      <p>Subtasks 3 and 4. Non-contextual and contextual binary
classi cation for Mexican Spanish
The subtasks of contextual and non-contextual binary classi cation for
MexicanSpanish were ranked by macro-averaged F1-score of the o ensive class. Similar
to subtasks 1 and 2, the number of participants was lower in the contextual
subtask, with only three participants in subtask 4.</p>
      <p>Table 8 depicts the results achieved individually for each of our runs in
subtask 3, non-contextual binary classi cation for Mexican Spanish. Similar to
subtask 1 and subtask 2, the rst run consisted of an ensemble based on
logistic regression from the probabilities of the neural networks models trained with</p>
      <p>OFG
psycholinguistic processes</p>
      <p>negative
psycholinguistic processes</p>
      <p>negative general
stylometry corpus words count</p>
      <p>register offensive speech
stylometry corpus syllabes count</p>
      <p>stylometry corpus length
register informal speech swear
stylometry corpus words per</p>
      <p>sentence
stylometry corpus inflesz
stylometry corpus readability
0%
25%
50%
75%
100%
only one feature set (BE, LF, NE, SE, and BF). We achieved a macro-averaged
F1-score of 66.7791%. Our second run is the one that is on the leader board and
it consisted of removing the linguistic features (LF and NE). We can observe
than in this case, better results are achieved for macro-averaged metrics. One
explanation for this fact is that the linguistic and negation features could
provide contradictory results for Mexican Spanish as they were designed for generic
Spanish. Third run also consisted of an ensemble based on regression but
using BE, LF, NE, and BF. We achieved better results than in the rst run by
excluding the SE features.</p>
      <p>For subtask 3 we selected our second run as o cial result. Table 9 depicts
the results of the leader board for this subtask. We reached position 5 in the
rank with a macro-averaged F1-score of the o ensive class of 67.0588%. The best
result was achieved by vic gomez with a macro-averaged F1-score of 70.2619%.
Compared with the best results, we achieved a similar macro-averaged recall
score, even greater than the two best overall submits, but their macro-averaged
precision was higher (76% and 75% vs. our 66.50%). Other teams achieved even
greater macro-averaged precision (xjywing with 88.8333%, aomar with 87.5000%,
and 91.8333%) with smaller macro-averaged recall.</p>
      <p>Regarding subtask 4, contextual binary classi cation for Mexican Spanish,
we sent three runs whose results are shown in Table 10. The rst one, consisted
of an ensemble model based on logistic regression of neural networks models for
the following feature set: LF, NE, BE, BF, SE, and CF. In the second run, we
sent the same model but we adjusted the CF features by using Robust Scaler, as
we found heavy outliers in the data. However, as we can observe, the results were
the same that we achieved with our rst run. Finally, our third run consisted
of an ensemble with the following feature set: LF, NE, BF, and CF. Compared
with the rst run, we removed SE. This run was submitted because we achieved
good results with our custom validation set.</p>
      <p>In subtask 4, as previously stated, we submit the third run to the o cial
leader board, that achieve slightly better macro-averaged precision and slightly
worse macro-averaged recall than the other two runs. Table 11 depicts the
ofcial ranking for subtask 4. Only three teams sent runs for this subtask. We
achieved the rst position, with a macro-averaged F1-score for the o ensive class
of 66.9449%, improving slightly our results from the previous subtask. Compared
with the second best result, we achieved slightly worse macro-averaged recall but
higher macro-averaged precision.</p>
      <p>non-offensive offensive
register offensive speech strong</p>
      <p>social media mentions
register offensive speech
morphosyntax morphology verbs
subjunctive compound pluperfect
morphosyntax morphology verbs</p>
      <p>function main
morphosyntax morphology verbs</p>
      <p>nonfinite infinitive
lexical social analytic
psycholinguistic processes</p>
      <p>negative general
social media jargon
errors orthographics misspelled
words
0%
25%
50%
75%
100%
Fig. 2. Mutual Information of the ten top-ranked linguistic features averaged by label
for the Mexican-Spanish dataset</p>
      <p>Figure 2 shows the ten top-ranked linguistic features for the Spanish
Mexican dataset averaged by label. As it was expected, linguistic features related
to o ensive speech are highly related to the o ensive class but it also appears
signi cantly on tweets labelled as non-o ensive, which suggests that there are
texts considered as non-o ensive that contain o ensive words. Regarding social
media, the usage of mentions is most common on o ensive tweets, which
suggests that o ensive speech is more common to individuals than groups. However,
social media jargon that includes words such as retweets, posts, or direct
messages are more common on non-o ensive tweets. The rest of the features only
have slightly variations regarding the label, as happens on the usage of verbs on
subjunctive compound pluperfect or the number of misspellings that are slightly
more common on o ensive tweets. On contrasts, verbs in in nitive, or analytic
thinking are more common on non-o ensive tweets.
6</p>
    </sec>
    <sec id="sec-6">
      <title>Conclusions</title>
      <p>In this working notes we describe the participation of the UMUTeam in the task
MeO endES regarding o ensive language detection in di erent variants of
Spanish. Our proposal for solving the di erent subtasks have been grounded on the
combination of linguistic and negation features with state-of-the-art
transformers, combined as ensembles of neural networks classi ers or combined in the same
neural network. Our results have achieved very good results in the o cial leader
board. We reached the rst position on subtasks 2 and 4 regarding o ensive
detection with contextual features on generic and Mexican Spanish respectively,
and position 2 and 5 on the non-contextual subtasks. It is worth mentioning,
however, that the number of participants who sent runs for contextual tasks was
lower than for non-contextual features tasks.</p>
      <p>The following insights were obtained during the participation in this task.
First, the results achieved indicate that linguistic features and transformers
mutually bene t from each other, increasing their reliability. Our results indicate
that ensembles learned from training a logistic regression machine-learning
classi er from the individual probabilities of each model achieve better results than
ensembles based on the mode (the label most voted) or the weighted mode.
Second, we observe than sentence- xed embeddings from the ne-tuned model of
BETO, which we called BF, outperform plain BE vectors in all cases, and it
is more easier to combine them with other feature sets. Third, during the
hyperparameter evaluation stage we observed that simpler neural network models
with only a few layers and few neurons behave better than models with more
than four hidden layers. Forth, we found that those linguistic features concerning
negative processes, such as anger, sadness, anxiety, are discriminatory features
regarding o ensive language detection. However, our results suggest that these
features are reliable to distinguish between non-o ensive documents from the
ones that include o ensive or vulgar language but not to di erentiate among
di erent types of o ensive language.</p>
      <p>Lastly, we are pleased with the opportunity we have been give to participate
in this task. This work has been a collaboration between Universidad de Murcia
and Universidad de Jaen.</p>
    </sec>
    <sec id="sec-7">
      <title>Acknowledgments</title>
      <p>This work was supported by the Spanish National Research Agency (AEI)
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