Cited by 63Natural Language Processing TechniquesTopic ModelingSpeech Recognition and Synthesis

Looking for a Needle in a Haystack: A Comprehensive Study of Hallucinations in Neural Machine Translation

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Guerreiro, Nuno M., Voita, Elena, Martins, André·2023·Proceedings of the 17th Conference of the European Chapter of the Association for Computational Linguistics

Abstract

Although the problem of hallucinations in neural machine translation (NMT) has received some attention, research on this highly pathological phenomenon lacks solid ground.Previous work has been limited in several ways: it often resorts to artificial settings where the problem is amplified, it disregards some (common) types of hallucinations, and it does not validate adequacy of detection heuristics.In this paper, we set foundations for the study of NMT hallucinations.First, we work in a natural setting, i.e., in-domain data without artificial noise neither in training nor in inference.Next, we annotate a dataset of over 3.4k sentences indicating different kinds of critical errors and hallucinations.Then, we turn to detection methods and both revisit methods used previously and propose using glass-box uncertainty-based detectors.Overall, we show that for preventive settings, (i) previously used methods are largely inadequate, (ii) sequence log-probability works best and performs on par with reference-based methods.Finally, we propose DEHALLUCINATOR, a simple method for alleviating hallucinations at test time which significantly reduces the hallucinatory rate.

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Cited by

Sorted by citations

Authors
Guerreiro, N. M., Voita, E., & Martins, A.
Affiliations
  • Instituto de Telecomunicações (PT)
  • University of Edinburgh (GB)
Corresponding author
Martins, André
Venue
Proceedings of the 17th Conference of the European Chapter of the Association for Computational Linguistics
Published
2023
Pages
1059-1075
OpenAlex
W4386566643
Cited by
63
References
7
Citations by year
2026: 10 · 2025: 11 · 2024: 17 · 2023: 24 · 2022: 1
FWCI
10.99
Type
conference paper
Language
en
Open access
Licence
cc-by
Locations
  • Conference of the European Chapter of the Association for Computational Linguistics (publishedVersion, cc-by)
  • arXiv (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Funders
  • HORIZON EUROPE Framework Programme (101070631)
  • Fundação para a Ciência e a Tecnologia (UIDB/50008, UIDB/50008/2020, -01-0247-, 50008, LISBOA - 01-0247, P2020)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Natural Language Processing Techniques
  • Physical Sciences › Computer Science › Artificial Intelligence › Topic Modeling
  • Physical Sciences › Computer Science › Artificial Intelligence › Speech Recognition and Synthesis
Keywords
hallucinations, neural machine translation, hallucination detection

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