The article presents a comprehensive evaluation of supervised fine-tuning and prompt-based approaches for the automated detection of conspiracy theories in German-language Telegram messages. The authors utilize the TelCovACT dataset, which contains around 4,000 messages randomly sampled from public Telegram channels known for disseminating conspiracy narratives during the COVID-19 pandemic, without relying on keyword-based filtering.
The supervised fine-tuning approach using the BERT-based model TelConGBERT achieves an F1 score of 0.79 for the positive class (conspiracy theory) and a macro-averaged F1 score of 0.85 on the test set. This performance is comparable to models trained on English keyword-based online datasets. The model also demonstrates moderate to good transferability when applied to data from later time ranges and a broader set of channels.
The authors also evaluate prompt-based approaches using the large language models GPT-3.5, GPT-4, and Llama 2. The best performing model is GPT-4, which achieves an F1 score of 0.79 for the positive class in a zero-shot setting when provided with a custom definition of conspiracy theories. The performance of GPT-3.5 and Llama 2 is less robust, with their outputs being sensitive to minor prompt variations.
The article further analyzes the models' performance in relation to the fragmentation of conspiracy narratives, finding that both TelConGBERT and GPT-4 struggle more with highly fragmented narratives. While the two models achieve comparable overall performance, their predictions disagree on 15% of the test data, suggesting differences in their underlying reasoning.
The authors discuss the practical implications of their findings, highlighting the trade-offs between supervised fine-tuning and prompt-based approaches in terms of resource requirements and robustness. They also outline plans for future work, including collaborating with NGOs to optimize the real-world deployment of TelConGBERT and exploring strategies for efficiently updating the training data.
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