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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Mario at EXIST 2025: A Simple Gateway to Efective Multilingual Sexism Detection</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Lin Tian</string-name>
          <email>Lin.Tian-3@uts.edu.au</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Johanne R. Trippas</string-name>
          <email>j.trippas@rmit.edu.au</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Marian-Andrei Rizoiu</string-name>
          <email>Marian-Andrei.Rizoiu@uts.edu.au</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>RMIT University</institution>
          ,
          <addr-line>Melbourne</addr-line>
          ,
          <country country="AU">Australia</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>University of Technology Sydney</institution>
          ,
          <addr-line>Sydney</addr-line>
          ,
          <country country="AU">Australia</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2025</year>
      </pub-date>
      <abstract>
        <p>This paper presents our approach to EXIST 2025 Task 1, addressing text-based sexism detection in English and Spanish tweets through hierarchical Low-Rank Adaptation (LoRA) of Llama 3.1 8B. Our method introduces conditional adapter routing that explicitly models label dependencies across three hierarchically structured subtasks: binary sexism identification, source intention detection, and multilabel sexism categorization. Unlike conventional LoRA applications that target only attention layers, we apply adaptation to all linear transformations, enhancing the model's capacity to capture task-specific patterns. In contrast to complex data processing and ensemble approaches, we show that straightforward parameter-eficient fine-tuning achieves strong performance. We train separate LoRA adapters (rank=16, QLoRA 4-bit) for each subtask using unified multilingual training that leverages Llama 3.1's native bilingual capabilities. The method requires minimal preprocessing and uses standard supervised learning. Our multilingual training strategy eliminates the need for separate languagespecific models, achieving 1.7-2.4% F1 improvements through cross-lingual transfer. With only 1.67% trainable parameters compared to full fine-tuning, our approach reduces training time by 75% and model storage by 98%, while achieving competitive performance across all subtasks (ICM-Hard: 0.6774 for binary classification, 0.4991 for intention detection, 0.6519 for multilabel categorization).</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Sexism Detection</kwd>
        <kwd>Low-Rank Adaptation</kwd>
        <kwd>Hierarchical Classification</kwd>
        <kwd>Social Media Analysis</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Everyday sexism – ranging from overt misogyny to subtle and implicit forms of gendered
microaggressions – undermines women’s psychological well-being, silences their voices, and perpetuates structural
inequality in digital spaces [
        <xref ref-type="bibr" rid="ref1 ref2">1, 2</xref>
        ]. Social networks, while instrumental in mobilizing feminist activism
through movements like #MeToo, #8M, and #Time’sUp, are also vehicles for the large-scale
dissemination of harmful stereotypes and normalized discrimination. Recent research has demonstrated the
concerning rise of harmful discourse during crisis events [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ], highlighting the urgent need for robust
detection systems that can identify not only explicit sexism but also the subtle ways gender-based
discrimination infiltrates mainstream online discussions [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ].
      </p>
      <p>The scale of this problem demands automated solutions. Manual content moderation cannot keep
pace with the billions of posts generated daily [5], yet existing detection systems often fail to capture
the nuanced ways sexism manifests online. Context matters: a tweet reporting sexist experiences difers
fundamentally from one perpetrating sexism, though both may contain similar language. Cultural
and linguistic variations further complicate detection, as sexist expressions evolve rapidly and difer
across communities. Research on behavioral homophily has shown that users can exhibit similar
engagement patterns when discussing diferent topics [ 6], suggesting that understanding user intent and
content categorization requires modeling hierarchical label dependencies. These challenges necessitate
sophisticated approaches that can distinguish whether content is sexist, understand its intent, categorize
its specific manifestation, and operate efectively across languages.</p>
      <p>The EXIST 2025 shared task [7] provides a comprehensive framework for advancing sexism detection
research. For the first time, the task spans three modalities (text, images, and videos) and two languages
(English and Spanish), reflecting the multimodal and multilingual nature of contemporary social media.
We focus on Task 1, which addresses text-based sexism detection through three hierarchically structured
subtasks: (i) binary sexism identification – determining whether content contains sexism; (ii) source
intention classification – distinguishing between direct sexism, reported experiences, and judgmental
commentary; and (iii) sexism type categorization – classifying content into specific categories such as
ideological inequality, stereotyping, objectification, sexual violence, and misogyny.</p>
      <p>Traditional approaches to these tasks have relied on task-specific models, often struggling with the
hierarchical dependencies between subtasks and requiring separate systems for each language. Building
on advances in multi-task learning for hate speech detection [8, 9], we present a unified framework
leveraging Low-Rank Adaptation (LoRA) [10] of Llama 3.1 8B [11] that addresses all three subtasks
simultaneously while maintaining computational eficiency. Our key innovation lies in hierarchical
label-aware routing, where LoRA adapters are conditionally activated based on parent-task predictions,
explicitly modeling the structured relationships between tasks.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related Work</title>
      <p>The automatic detection of sexism on social media has gained increasing attention within the natural
language processing (NLP) community, motivated by the need to mitigate online harassment and
promote equitable digital discourse. This section reviews existing work in four parts: (i) evolution
of sexism detection tasks and methodologies, (ii) advances in text-based classification approaches,
(iii) recent developments in large language model (LLM) adaptation for this domain, and (iv) harmful
content detection and moderation research that informs our understanding of sexism as part of the
broader landscape of online harmful content.</p>
      <sec id="sec-2-1">
        <title>2.1. Evolution of Sexism Detection Tasks</title>
        <p>
          Early work in online sexism detection focused primarily on binary classification of overtly hateful
content. Talat and Hovy [
          <xref ref-type="bibr" rid="ref1">1</xref>
          ] proposed with their Twitter dataset distinguishing sexist, racist, and neutral
content. However, researchers quickly recognized that sexism manifests across a spectrum from explicit
misogyny to subtle linguistic biases, necessitating more nuanced approaches.
        </p>
        <p>The EXIST shared tasks have been instrumental in advancing the field since 2021 [ 12, 13, 14]. These
tasks progressively introduced hierarchical classification schemes, distinguishing between sexism
identification, intention categorization, and fine-grained typing. Similarly, the SemEval-2023 Task 10
on Explainable Detection of Online Sexism (EDOS) [15] focused on interpretability alongside detection
accuracy. In addition, the field has evolved from feature-engineered approaches using lexicons and
n-grams [16] to neural architectures. Early deep learning approaches used CNNs and LSTMs [17, 18],
achieving strong improvements over traditional classifiers. The introduction of transformer-based
models marked another paradigm shift, with BERT [19] and its variants becoming the de facto standard
for sexism detection tasks [20].</p>
        <p>Recent work has explored multi-task learning frameworks to jointly model related tasks. For example,
Samory et al. [21] showed that jointly learning sexism and racism detection improves performance on
both tasks. Chiril et al. [22] extended this to emotion and target identification, showing the benefits
of auxiliary task learning for sexism detection. Building on this foundation, Yuan and Rizoiu [9]
demonstrated that multi-task learning across multiple hate speech datasets substantially improves
generalization to previously unseen datasets, achieving consistent improvements in cross-domain
scenarios through their leave-one-out evaluation scheme.</p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. Text-based Classification for Sexism Detection</title>
        <p>Text remains the primary modality for sexism detection, given its prevalence in social media discourse.
The unique challenges of social media text – including informal language, code-switching, and
platformspecific conventions – have shaped methodological developments in this area.</p>
        <p>The evolution of representation learning has been particularly influential in capturing subtle sexist
language. Early approaches relied on static word embeddings such as Word2Vec [23] and GloVe [24],
which provided limited context sensitivity. The transition to contextual representations marked a
significant advancement, with transformer-based encoders pre-trained on social media data demonstrating
superior performance. Models like BERTweet [25] and TweetEval [26] excel at modeling
platformspecific linguistic patterns, including hashtags, mentions, and abbreviated expressions common in
online discourse.</p>
        <p>Cross-lingual sexism detection has emerged as a research direction, particularly through the
development of multilingual models. While mBERT [19] and XLM-RoBERTa [27] have enabled approaches
across languages, their efectiveness varies. The EXIST shared tasks have consistently featured
SpanishEnglish tracks, with top-performing systems leveraging language-agnostic representations. However,
Nozza [28] revealed persistent performance disparities across languages, with multilingual models often
underperforming on low-resource languages despite their theoretical universality.</p>
        <p>The importance of domain-specific adaptation has been reported through multiple studies. Chiril
et al. [29] demonstrated that models trained on general ofensive language datasets exhibit performance
degradation when applied to sexism-specific tasks, highlighting the unique linguistic characteristics
of gender-based harassment. This finding motivated the creation of specialized resources, such as
the expert-annotated datasets introduced by Guest et al. [30], designed to capture implicit forms of
sexism that automated systems frequently miss. Yuan et al. [8] further advanced this area by proposing
transfer learning techniques that leverage multiple independent datasets jointly, constructing unified
hate speech representations that enable efective cross-dataset knowledge transfer while reducing
annotation requirements.</p>
      </sec>
      <sec id="sec-2-3">
        <title>2.3. Large Language Model Adaptation</title>
        <p>LLMs have introduced new possibilities for automated sexism detection [31]. However, this application
remains comparatively underexplored in NLP, compared to more extensively studied tasks such as
sentiment analysis, summarization, or machine translation.</p>
        <p>Initial investigations into prompt-based approaches revealed both promise and limitations. For
example, Chiu et al. [32] showed that carefully engineered prompts enable models like GPT-3 [33]
to achieve competitive zero-shot performance on hate speech detection tasks. However, subsequent
work by Yin and Zubiaga [34] identified critical weaknesses: prompt-based methods struggle with
implicit sexism and exhibit high sensitivity to prompt formulation, resulting in inconsistent predictions
across semantically equivalent queries. However, recent advances in parameter-eficient fine-tuning
methods present alternatives to full model adaptation. While techniques like LoRA [10] have succeeded
in various domains, their application to hierarchical sexism detection remains underexplored. Our work
addresses this gap by demonstrating that comprehensive LoRA adaptation with hierarchical routing
can efectively model the multi-level nature of sexism categorization, achieving strong performance
while maintaining computational eficiency.</p>
      </sec>
      <sec id="sec-2-4">
        <title>2.4. Harmful Content Detection and Moderation</title>
        <p>Understanding sexism detection requires broader context about harmful content dynamics and
moderation efectiveness. Sexism represents a significant category within the wider ecosystem of harmful
online content, and methodological advances in general harmful content detection can be leveraged
for gender-based harassment identification. Recent research has revealed concerning patterns in how
various forms of harmful content spread across social media platforms. Kong et al. [35] demonstrated
that coordinated harmful content campaigns can be detected through the social system reactions they
elicit, using interval-censored transformer approaches to identify coordinated behavior patterns with
high accuracy. This work has important implications for sexism detection, as it shows how temporal
patterns and user engagement can reveal coordinated campaigns of gender-based harassment,
suggesting that sexism detection systems can benefit from approaches originally developed for broader
harmful content identification.</p>
        <p>The importance of early detection in harmful content mitigation has been further emphasized by
recent advances in engagement prediction models. Tian et al. [36] developed IC-Mamba, a state space
model that excels at forecasting social media engagement within the crucial first 15-30 minutes of
posting, enabling rapid assessment of content reach and early identification of potentially problematic
content. Their approach to modeling interval-censored data with integrated temporal embeddings
provides valuable insights for sexism detection systems, as early engagement patterns could signal the
viral potential of sexist content, allowing for more timely intervention strategies.</p>
        <p>Understanding the causal mechanisms underlying harmful content spread is equally critical for
efective detection and intervention. Tian and Rizoiu [37] introduced a novel joint treatment-outcome
framework that distinguishes correlation from causation in social media influence analysis, particularly
for misinformation spread. Their approach adapts causal inference techniques to estimate Average
Treatment Efects within the sequential nature of social media interactions, addressing challenges
from external confounding signals. This work has important implications for sexism detection, as
understanding the true causal influence of sexist content on user engagement can inform more targeted
intervention strategies and help distinguish organic spread from coordinated amplification campaigns.
In addition, Schneider and Rizoiu [5] showed that faster content moderation reduces harm from the
most severe content, even on high-trafic platforms like Twitter. Using self-exciting point processes,
the study highlights the urgent need for timely responses, an insight directly applicable to real-world
sexism detection systems targeting gender-based harassment.</p>
        <p>Research on opinion dynamics and intervention strategies ofers additional perspectives relevant
to sexism detection as part of broader harmful content mitigation. Calderon et al. [38] introduced
the Opinion Market Model to evaluate positive interventions for stemming harmful opinion spread,
demonstrating how media coverage can modulate the dissemination of problematic content. This
framework provides valuable insights for understanding how sexist discourse spreads and how detection
systems might be integrated with intervention strategies targeting various forms of harmful content.</p>
        <p>
          Studies of extreme opinion infiltration have revealed the pathways through which harmful discourse
enters mainstream conversations. Kong et al. [
          <xref ref-type="bibr" rid="ref4">4</xref>
          ] employed mixed-method approaches to show how
extreme opinions gradually infiltrate online discussions, with their human-in-the-loop methodology
providing insights into the dynamics of problematic speech evolution from conservative to extreme
viewpoints. These findings are particularly relevant for sexism detection, as they highlight the
importance of capturing subtle shifts in discourse that may not be immediately apparent through traditional
classification approaches, and demonstrate how techniques developed for general harmful content can
be adapted for gender-specific harassment detection.
        </p>
        <p>
          The study of harmful discourse during crisis events provides additional context for understanding
sexist content dynamics within broader patterns of problematic online behavior. Bailo et al. [
          <xref ref-type="bibr" rid="ref3">3</xref>
          ]
analyzed the performance of far-right Twitter users during the Australian bushfires and COVID-19
pandemic, revealing how accounts promoting harmful content moved from peripheral to central
positions in disaster-driven conversations. Their work demonstrates the importance of monitoring
evolving discourse patterns, as the association between information disorder and overperformance of
accounts spreading harmful content suggests systematic coordination that may include gender-based
harassment campaigns.
        </p>
        <p>Recent work on ideology detection has also informed approaches to sexism identification within
the broader harmful content landscape. Ram et al. [39] presented an end-to-end ideology detection
pipeline that constructs context-agnostic ideological signals from media slant data, demonstrating
efective detection of extreme ideologies alongside psychosocial profiling. Their approach ofers valuable
methodological insights for sexism detection, particularly in terms of developing automatic signal
generation that reduces dependence on manual annotation while maintaining detection accuracy across
diferent types of harmful content.</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. Methodology</title>
      <p>We present our methodology for EXIST 2025 Task 1, which uses parameter-eficient fine-tuning of
Llama 3.1 8B [11] using LoRA with hierarchical label-aware routing to address all three subtasks across
English and Spanish. Our approach leverages a unified multilingual model with task-specific adapters
and conditional specialization based on the hierarchical label structure.</p>
      <sec id="sec-3-1">
        <title>3.1. Task Formulation</title>
        <p>We formulate the three EXIST 2025 Task 1 subtasks as follows:</p>
        <p>Subtask 1.1 - Binary Sexism Identification : A binary classification problem where the model
determines whether a given tweet contains sexist content (SEXIST vs. NOT_SEXIST).</p>
        <p>Subtask 1.2 - Source Intention Detection: A multiclass classification task that categorizes the
intention behind sexist tweets into three categories:
• DIRECT: Messages that are inherently sexist or incite sexist behavior
• REPORTED: Messages that report sexist situations experienced by women
• JUDGEMENTAL: Messages that judge or criticize sexist behavior</p>
        <p>Subtask 1.3 - Sexism Categorization: A multilabel classification task that categorizes sexist content
according to five types:
• IDEOLOGICAL_AND_INEQUALITY
• STEREOTYPING_AND_DOMINANCE
• OBJECTIFICATION
• SEXUAL_VIOLENCE
• MISOGYNY_AND_NON_SEXUAL_VIOLENCE</p>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. LoRA Configuration and Target Module Selection</title>
        <p>We used LoRA for parameter-eficient finetuning, with attention to target module selection. While
conventional approaches often restrict LoRA adaptation to attention weight matrices, our experiments
showed that module targeting yields better performance.</p>
        <p>Specifically, we applied LoRA decomposition to all linear transformation layers in the model
architecture: the attention mechanism components (q_proj, k_proj, v_proj, o_proj), the feed-forward
network layers (gate_proj, up_proj, down_proj), and the language modeling head (lm_head).
For each target module, we introduced trainable low-rank matrices with rank  = 16, following the
parameterization:</p>
        <p>= 0 + ,
where 0 represents the frozen pretrained weights, and  ∈ R× ,  ∈ R×  are the trainable
adaptation matrices initialized with  ∼  (0,  2) and  as zeros.</p>
        <p>Table 1 summarizes our complete configuration for both LoRA hyperparameters and training settings.
We selected rank  = 16 to balance adaptation capacity with memory eficiency, while maintaining
computational feasibility through 4-bit quantization and gradient checkpointing. The use of Flash
Attention v2 [40] further accelerates training without compromising model quality.</p>
        <p>This configuration enables eficient fine-tuning while preserving the model’s multilingual capabilities,
which is crucial for our unified approach to handling English and Spanish data. The comprehensive
targeting of all linear layers, rather than just attention matrices, provides the flexibility to capture
task-specific patterns across the hierarchical sexism detection tasks.</p>
      </sec>
      <sec id="sec-3-3">
        <title>3.3. Hierarchical Label-Aware Adaptation with LoRA</title>
        <p>To model the hierarchical structure of the subtasks, we implement a level-specific LoRA routing
mechanism. The hierarchy includes three levels: (i) binary sexism detection, (ii) source intention
classification, and (iii) sexism type categorization. For each level ℓ ∈ {1, 2, 3}, we define a dedicated
LoRA module Δ(ℓ) that adapts the shared language model  .</p>
        <p>During training, adapter routing is conditioned on the gold parent labels. At inference, predictions
proceed sequentially from the top level, with the model using the predicted label ^(ℓ− 1) to activate the
corresponding LoRA module Δ(ℓ) for the current level. This design supports conditional specialization
while maintaining parameter eficiency.</p>
        <p>The hidden representation at level ℓ is computed as:
h(ℓ) =  () + Δ(ℓ)
^(ℓ− 1) ().</p>
        <p>In addition to standard task-specific losses (e.g., cross-entropy for classification and binary
crossentropy for multi-label prediction), we introduce a soft constraint that penalizes invalid parent-child
label transitions, thereby encouraging structured coherence across the hierarchy in:
 3
ℒhierarchy =  ∑=︁1 ∑ℓ=︁2 I[^(ℓ− 1) = NOT_SEXIST] · m∈a(xℓ) (ℓ)(),
where  is the hierarchy constraint weight,  is the number of instances, ^(ℓ− 1) is the predicted label

(ℓ)() is the predicted probability
at level ℓ − 1 for instance , (ℓ) is the set of valid classes at level ℓ, 
for class  at level ℓ, and I[· ] is the indicator function. This constraint specifically penalizes cases where
a non-sexist prediction at the binary level is followed by high-confidence predictions at subsequent
hierarchical levels.</p>
        <p>The total training objective combines task-specific losses with the hierarchical consistency constraint:
3
ℒtotal = ∑︁ ℒt(aℓs)k + ℒhierarchy,</p>
        <p>ℓ=1
where ℒ(taℓs)k represents the standard loss at each level: cross-entropy for binary and multiclass
classification tasks, and binary cross-entropy for the multilabel categorization task.</p>
      </sec>
      <sec id="sec-3-4">
        <title>3.4. Data Processing and Multilingual Strategy</title>
        <p>Our approach uses a straightforward supervised learning methodology with gold standard labels for
training:</p>
        <p>Label Processing: We use the provided gold standard labels for each subtask, treating each
tweetlabel pair as a standard supervised learning instance. While the EXIST 2025 dataset includes multiple
annotations per instance under the Learning with Disagreement paradigm, our methodology focuses
on the gold labels for eficient and direct optimization.</p>
        <p>Input Formatting: Tweets are formatted using Llama 3.1’s instruction template structure:
&lt;|begin_of_text|&gt;&lt;|start_header_id|&gt;system&lt;|end_header_id|&gt;
[Task-specific system prompt]&lt;|eot_id|&gt;
&lt;|start_header_id|&gt;user&lt;|end_header_id|&gt;
[Tweet text]&lt;|eot_id|&gt;
&lt;|start_header_id|&gt;assistant&lt;|end_header_id|&gt;
[Classification output]&lt;|eot_id|&gt;</p>
        <p>Text Preprocessing: Minimal preprocessing is applied to preserve the authentic social media
language characteristics. We maintain original tweet formatting, including hashtags, mentions, and
emoji, as these elements often carry semantic significance for sexism detection.</p>
        <p>Multilingual Strategy: We apply a unified multilingual approach, training a single model on both
English and Spanish data simultaneously, leveraging Llama 3.1’s native bilingual capabilities. Rather
than training separate language-specific models, we hypothesize that joint bilingual training enhances
cross-lingual transfer learning and improves overall performance by exposing the model to diverse
linguistic expressions of sexism across both languages. This approach is inspired by recent work
showing that transfer learning across hate speech datasets can achieve substantial improvements in
generalization [9], and our multilingual strategy extends this principle to cross-lingual knowledge
transfer.</p>
        <p>Training Strategy: We fine-tune separate LoRA adapters for each subtask–binary classification
for sexism identification (1.1), multiclass for source intention detection (1.2), and multilabel for
sexism categorization (1.3)–optimizing each for its specific classification requirements. All adapters are
trained using standard supervised learning with gold standard labels on the combined English-Spanish
dataset, leveraging cross-lingual transfer to ensure robust bilingual performance without requiring
separate language-specific models. Training continues until convergence while monitoring validation
performance, with early stopping applied when validation loss plateaus to prevent overfitting.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Experimental Results</title>
      <sec id="sec-4-1">
        <title>4.1. Cross-lingual Training Analysis</title>
        <p>To validate our unified multilingual training strategy, we conducted ablation studies comparing joint
bilingual training against separate language-specific models. Table 2 presents performance comparisons
across all three subtasks.</p>
        <p>Joint bilingual training consistently outperforms language-specific models across all subtasks, with
F1 improvements ranging from 1.7 − 2.4 percentage points. These gains validate our hypothesis
that cross-lingual transfer enhances sexism detection by leveraging shared semantic patterns across
languages, consistent with findings from transfer learning research in hate speech detection [ 8]. The
improvements are particularly obvious for the multilabel categorization task (+2.4), suggesting that
complex semantic distinctions benefit most from exposure to diverse linguistic expressions of sexism.</p>
        <p>The bidirectional nature of cross-lingual transfer manifests itself in consistent improvements for both
languages. Spanish, despite typically having fewer training instances in multilingual datasets, achieves
comparable or slightly higher gains than English across all subtasks. This symmetric improvement
pattern indicates efective knowledge sharing, where English contributes richer training signal while
Spanish provides complementary linguistic patterns and cultural-specific expressions of sexism.</p>
        <p>These findings have important implications for multilingual sexism detection systems. Rather
than maintaining separate models per language – which requires duplicated development efort and
computational resources – our joint training approach achieves superior performance with a single
unified model.</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Task-Specific Performance Analysis</title>
        <p>Our approach achieved first place across all three subtasks, showing the efectiveness of hierarchical
LoRA adaptation with comprehensive module targeting. Spanish consistently outperforms English
across all subtasks, with particularly pronounced diferences in intention detection ( +0.23 ICM-Hard)
and sexism categorization (+0.26 ICM-Hard). This cross-lingual performance gap likely reflects both
diferences in training data distribution and linguistic characteristics of sexist expressions across
languages, suggesting that sexist discourse may manifest through more identifiable patterns in Spanish
social media text.</p>
        <p>As expected, performance decreases with task complexity, from binary classification (0.6774) to the
more nuanced intention detection task (0.4991). This progression aligns with the inherent dificulty
of fine-grained semantic understanding required for distinguishing between direct sexism, reported
experiences, and judgmental commentary. Interestingly, the multilabel categorization task achieves
intermediate performance (0.6519), suggesting that our hierarchical approach efectively leverages
parent-level predictions to guide more complex downstream classifications.</p>
        <p>The strong performance on hierarchically dependent tasks validates our design choice of conditional
LoRA routing. Despite the challenging nature of intention detection – which requires understanding
pragmatic context and author stance – our model maintains competitive performance by conditioning
adapter selection on binary sexism predictions. This shows that explicitly modeling label dependencies
through hierarchical specialization provides tangible benefits for complex, structured classification
scenarios in social media discourse analysis.</p>
      </sec>
      <sec id="sec-4-3">
        <title>4.3. Eficiency Analysis and Ablation Study</title>
        <p>Our LoRA-based approach achieves substantial computational eficiency compared to full fine-tuning
while maintaining competitive performance. Table 4 demonstrates that our method reduces trainable
parameters by 98.33% (from 8.03B to 134M), enabling training on consumer-grade GPUs with only
12GB memory compared to the 32GB required for full fine-tuning. This eficiency translates to 4x faster
training times and 64x smaller storage footprint per task-specific adapter, making the deployment
practical and cost-efective.</p>
        <p>To validate our hyperparameter selection, we conducted ablation studies examining the relationship
between LoRA rank and model performance. Table 5 shows results on Subtask 1.1, revealing that
rank 16 achieves optimal eficiency-performance trade-ofs. While higher ranks (32, 64) yield marginal
F1 improvements of less than 0.3%, they require 2-4x more parameters and proportionally increased
memory and training time. Our chosen configuration thus maximizes accessibility for researchers with
limited computational resources while achieving near-optimal performance across all subtasks.</p>
        <p>These eficiency gains are particularly crucial for the hierarchical multi-task nature of the shared
task, where separate adapters for each subtask would traditionally require 3x the storage and memory.
Our approach enables deployment of all three task-specific models within the memory constraints of a
single GPU.</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Conclusion</title>
      <p>This paper presents a simple yet highly efective approach to text-based sexism detection that achieved
ifrst-place performance in EXIST 2025 Task 1 across English and Spanish languages on hard label
evaluations. Our methodology demonstrates that straightforward Low-Rank Adaptation (LoRA)
finetuning of Llama 3.1 8B, combined with unified multilingual training, outperforms more complex
approaches while maintaining computational eficiency.</p>
      <p>Our key finding is that joint bilingual training consistently surpasses separate language-specific
models, achieving 1.7-2.4% improvements across all subtasks. The bidirectional knowledge transfer
between English and Spanish shows that shared semantic representations of sexist patterns can transcend
language boundaries while preserving language-specific nuances. This finding has broader implications
for multilingual classification tasks beyond sexism detection, extending previous work on cross-dataset
transfer learning [9, 8] to the cross-lingual domain.</p>
      <p>While our approach achieves strong performance through straightforward supervised learning,
incorporating demographic information into the fine-tuning process presents an opportunity for
improvement. The EXIST 2025 dataset includes rich annotator demographic information, including gender,
age, education level, ethnicity, and country of residence. Rather than discarding this valuable
information in favor of gold labels, future work could explore encoding these persona characteristics directly
into the LoRA adaptation process. This could involve persona-specific adapters [ 42], demographic-aware
attention mechanisms, or multi-task learning approaches that jointly optimize for sexism detection
while modeling annotator perspectives. Such persona-aware fine-tuning could capture the subjective
nature of sexism perception across diferent demographic groups, leading to more culturally-sensitive
detection systems.</p>
      <p>Furthermore, our hierarchical LoRA approach opens avenues for integration with broader harmful
content moderation frameworks [5] and opinion market models [38] that could provide real-time
intervention capabilities. Recent advances in early engagement prediction [36] suggest that combining our
sexism detection approach with temporal engagement forecasting could enable proactive identification
of potentially viral sexist content within the critical first minutes of posting. Additionally, incorporating
causal modeling approaches [37] could help distinguish between organic engagement and coordinated
amplification of sexist content, providing deeper insights into the true influence mechanisms underlying
gender-based harassment campaigns. Future work could explore how our sexism detection system
might be combined with positive intervention strategies to not only identify sexist content but also
guide counter-narrative generation or targeted educational interventions, contributing to more
comprehensive approaches for fostering equitable online discourse within the broader ecosystem of harmful
content mitigation.</p>
    </sec>
    <sec id="sec-6">
      <title>Declaration on Generative AI</title>
      <p>This work was created, reviewed, and edited by human authors. AI tools were used in two specific
capacities: (1) debugging the syntax errors and optimizations in the code components of the LoRA
framework, and (2) writing assistance to improve conciseness and readability of manuscript sections.</p>
      <p>For writing assistance, we used Claude (Anthropic) exclusively for grammatical error correction
and sentence-level clarity improvements. Example prompts included: “Identify grammatical errors
in this sentence” and “Keep concise, and improve reading flow. Match style. Highlight changes.
Break down complex and long sentences and make more concise.”. All AI-generated suggestions were
critically reviewed, modified, and integrated by human authors. The original conceptual content,
technical contributions, experimental design, analysis, and final editorial decisions remain entirely
human-authored. AI tools did not contribute to the research methodology, data analysis, or scientific
conclusions.
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