The paper presents the approach developed for the “Climate Activism Stance and Hate Event Detection” Shared Task at CASE 2024, comprising three sub-tasks. The Shared Task aimed to create a system capable of detecting hate speech, identifying the targets of hate speech, and determining the stance regarding climate change activism events in English tweets. The approach involved data cleaning and pre-processing, addressing data imbalance, and fine-tuning the “mistralai/Mistral-7B-v0.1” LLM for sequence classification using PEFT (Parameter-Efficient Fine-Tuning). The LLM was fine-tuned using two PEFT methods, namely LoRA and prompt tuning, for each sub-task, resulting in the development of six Mistral-7B fine-tuned models in total. Although both methods surpassed the baseline model scores of the task organizers, the prompt tuning method yielded the highest results. Specifically, the prompt tuning method achieved a Macro-F1 score of 0.8649, 0.6106 and 0.6930 in the test data of sub-tasks A, B and C, respectively.

We introduce a new corpus, named AIKIA, for Offensive Language Detection (OLD) in Modern Greek (EL). EL is a less-resourced language regarding OLD. AIKIA offers free access to annotated data leveraged from EL Twitter and fiction texts using the lexicon of offensive terms, ERIS, that originates from HurtLex. AIKIA has been annotated for offensive values with the Best Worst Scaling (BWS) method, which is designed to avoid problems of categorical and scalar annotation methods. BWS assigns continuous offensive scores in the form of floating point numbers instead of binary arithmetical or categorical values. AIKIA’s performance in OLD was tested by fine-tuning a variety of pre-trained language models in a binary classification task. Experimentation with a number of thresholds showed that the best mapping of the continuous values to binary labels should occur at the range [0.5-0.6] of BWS values and that the pre-trained models on EL data achieved the highest Macro-F1 scores. Greek-Media-BERT outperformed all models with a threshold of 0.6 by obtaining a Macro-F1 score of 0.92

The paper describes the system for the 4th Shared task on “Detecting Signs of Depression from Social Media Text” at LT-EDI@RANLP 2023, which aimed to identify signs of depression on English social media texts. The solution comprised data cleaning and pre-processing, the use of additional data, a method to deal with data imbalance as well as fine-tuning of two transformer-based pre-trained language models, RoBERTa-Large and DeBERTa-V3-Large. Four model architectures were developed by leveraging different word embedding pooling methods, namely a RoBERTa-Large bidirectional GRU model using GRU pooling and three DeBERTa models using CLS pooling, mean pooling and max pooling, respectively. Although ensemble learning of DeBERTa’s pooling methods through majority voting was employed for better performance, the RoBERTa bidirectional GRU model managed to receive the 8th place out of 31 submissions with 0.42 Macro-F1 score.

The paper describes the SemEval-2023 Task 10: “Explainable Detection of Online Sexism (EDOS)”, which investigates the detection of sexism on two social media sites, Gab and Reddit, by encouraging the development of machine learning models that perform binary and multi-class classification on English texts. The EDOS Task consisted of three hierarchical sub-tasks: binary sexism detection in sub-task A, category of sexism detection in sub-task B and fine-grained vector of sexism detection in sub-task C. My participation in EDOS comprised fine-tuning of different layer representations of Transformer-based pre-trained language models, namely BERT, AlBERT and RoBERTa, and ensemble learning via majority voting of the best performing models. Despite the low rank mainly due to a submission error, the system employed the largest version of the aforementioned Transformer models (BERT-Large, ALBERT-XXLarge-v1, ALBERT-XXLarge-v2, RoBERTa-Large), experimented with their multi-layer structure and aggregated their predictions so as to get the final result. My predictions on the test sets achieved 82.88%, 63.77% and 43.08% Macro-F1 score in sub-tasks A, B and C respectively.