How Well Does It Generalize? A Robustness Study of Hausa Machine-Generated Text Detection

Abdulhamid Abubakar, Faisal Muhammad Adam, Shamsuddeen Hassan Muhammad, Abubakar Auwal Khalid, Babangida Sani


Abstract
Sani et al. (2025) introduced the first dedicated Hausa machine-generated text (MGT) detec- tor, an AfroXLMR-large classifier trained on 2,586 paired articles from seven Hausa news outlets and Gemini 2.0 Flash, reporting F1 of 0.9921 on a headline-grouped split. They iden- tified three limitations of their work: a single news domain, a small batch and short train- ing schedule, and a single generator (Gemini 2.0 Flash) for the machine-generated data. We extend their work along the third axis. First, we replicate their reported result across four random seeds, obtaining F1 of 0.992 ±0.005. Test recall on the AI class is 1.000 at every seed. Second, we analyse the detector’s false positives. All errors fall on Human articles, and two native-speaker reviewers confirm these are genuine, natural Hausa journalism. The clear- est correlate of misclassification is the absence of numerical content: the median digit frac- tion is 0.0% in misclassified articles vs. 0.6% in correctly classified ones. Third, we test the detector on six non-training generators span- ning four model families. Detection rates span from 0% (Aya-Expanse 8B) to nearly 100% (Gemma 4). All three Google-family models in our experiment (training-distribution Gemini 2.0 Flash and the two non-training Gemma 4 variants) are detected at rates above 98% with mean P(machine) above 0.98. No non-Google generator exceeds 21%. Three contamination checks fail to explain this away: generated articles overlap very little with their human sources, detection barely moves when we re- move every article that shares a 13-gram with its source, and the Google output that gets de- tected is at least as diverse as everyone else’s, so it is not memorised or templated text. What the detector has learned looks less like a general Hausa MGT signal and more like a Gemini- family stylistic fingerprint. We discuss what this means for deployment, including a 3.1% false-positive rate on real Hausa journalists.
Anthology ID:
2026.winlp-main.5
Volume:
Proceedings of the 10th Widening NLP Workshop
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Chen Zhang, Emily Allaway, Meryem M’hamdi, Peerat Limkonchotiwat, Richard He Bai, Santosh T.Y.S.S., Surendrabikram Thapa, Yinqiao Li
Venues:
WiNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
48–60
Language:
URL:
https://aclanthology.org/2026.winlp-main.5/
DOI:
Bibkey:
Cite (ACL):
Abdulhamid Abubakar, Faisal Muhammad Adam, Shamsuddeen Hassan Muhammad, Abubakar Auwal Khalid, and Babangida Sani. 2026. How Well Does It Generalize? A Robustness Study of Hausa Machine-Generated Text Detection. In Proceedings of the 10th Widening NLP Workshop, pages 48–60, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
How Well Does It Generalize? A Robustness Study of Hausa Machine-Generated Text Detection (Abubakar et al., WiNLP 2026)
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PDF:
https://aclanthology.org/2026.winlp-main.5.pdf