How Faithful Are Your Summaries? A Study of NLI-Based Verification in Portuguese

  • Felipe S. F. Paula UFRGS
  • Matheus Westhelle UFRGS
  • Maria Cecília M. Corrêa UFRGS
  • Luciana R. Bencke UFRGS
  • Viviane P. Moreira UFRGS

Abstract


Abstractive summarization systems often generate content that is not supported by the source text, making faithfulness verification a critical evaluation step. In this paper, we investigate the reliability of Natural Language Inference (NLI) methods for detecting summary faithfulness in Portuguese. Our contribution is two-fold: (i) we introduce VERISUMM, the first large-scale dataset for summary faithfulness detection in Portuguese, and (ii) we benchmark several NLI-based approaches applied to faithfulness detection. Our experiments revealed that zero-shot models exhibit low to moderate performance and that fine-tuning improves results. However, our error analysis showed that NLI models rely heavily on lexical overlap heuristics, limiting their effectiveness.

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Published
2025-09-29
PAULA, Felipe S. F.; WESTHELLE, Matheus; CORRÊA, Maria Cecília M.; BENCKE, Luciana R.; MOREIRA, Viviane P.. How Faithful Are Your Summaries? A Study of NLI-Based Verification in Portuguese. In: BRAZILIAN SYMPOSIUM IN INFORMATION AND HUMAN LANGUAGE TECHNOLOGY (STIL), 16. , 2025, Fortaleza/CE. Anais [...]. Porto Alegre: Sociedade Brasileira de Computação, 2025 . p. 307-322. DOI: https://doi.org/10.5753/stil.2025.37834.