Rating–Text Mismatch in Brazilian Portuguese Reviews: How Reliable Are Zero-Shot LLMs?

Emanuelle Marreira, Carlos M. S. Figueiredo, Tiago de Melo


Abstract
This study evaluates the ability of large language models (LLMs) to detect incoherence between the text of product reviews and their assigned rating (1 or 5 stars). Using popular LLMs such as GPT-5, Llama-4 and DeepSeek-3.2, and models optimized for Brazilian Portuguese, Sabiá-3.1 and Bode-3.1, we show that some are capable of detecting incoherence among texts and ratings (F1 > 90%) in a zero-shot protocol. Models also present a high agreement in the predictions, where several prediction rounds led to low variability (Fleiss’ κ> 0.95). With the demonstrated incoherence present in all product categories (aprox. 10% of comments), the results suggest that LLMs are very promising to perform this high semantic interpretation task, and they can be used as valuable tools for online monitoring and recommendation systems.
Anthology ID:
2026.propor-1.96
Volume:
Proceedings of the 17th International Conference on Computational Processing of Portuguese (PROPOR 2026) - Vol. 1
Month:
April
Year:
2026
Address:
Salvador, Brazil
Editors:
Marlo Souza, Iria de-Dios-Flores, Diana Santos, Larissa Freitas, Jackson Wilke da Cruz Souza, Eugénio Ribeiro
Venue:
PROPOR
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
959–967
Language:
URL:
https://preview.aclanthology.org/ingest-dnd/2026.propor-1.96/
DOI:
Bibkey:
Cite (ACL):
Emanuelle Marreira, Carlos M. S. Figueiredo, and Tiago de Melo. 2026. Rating–Text Mismatch in Brazilian Portuguese Reviews: How Reliable Are Zero-Shot LLMs?. In Proceedings of the 17th International Conference on Computational Processing of Portuguese (PROPOR 2026) - Vol. 1, pages 959–967, Salvador, Brazil. Association for Computational Linguistics.
Cite (Informal):
Rating–Text Mismatch in Brazilian Portuguese Reviews: How Reliable Are Zero-Shot LLMs? (Marreira et al., PROPOR 2026)
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PDF:
https://preview.aclanthology.org/ingest-dnd/2026.propor-1.96.pdf