Fact over Fiction: Detection of Pathological Hallucinations in Sinhala-to-English Neural Machine Translation

Key points

• This vulnerability is acute in low-resource settings like Sinhala-to-English, where weak cross-lingual alignment leads to hallucinations.1
• This paper introduces a framework for reference-free hallucination detection in this language pair.1
• We present a 45,000-sample synthetic dataset generated through a probabilistic chain of five linguistically motivated corruption strategies, with a semantic rescue mechanism that uses character-level similarity to distinguish hallucinations from morphological variants.1
• We fine-tune mDeBERTa-v3 for token-level sequence labelling, reaching a token-level F1 of 0.841 +/- 0.001 over three seeds on a source-disjoint test set, and study a three-signal ensemble integrating neural risk scores, sequence log-probabilities, and cross-lingual semantic embeddings (LaBSE).1

Sources (1)

• [1]Fact over Fiction: Detection of Pathological Hallucinations in Sinhala-to-English Neural Machine Translation
  arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 8, 07:19 AM

  Neural Machine Translation (NMT) models, while capable of producing highly fluent outputs, remain vulnerable to hallucinations, which are translations that are natural yet semantically unrelated to the source.

  This vulnerability is acute in low-resource settings like Sinhala-to-English, where weak cross-lingual alignment leads to hallucinations.

Extractive summary: sentences quoted from the sources.