GLTR: Statistical Detection and Visualization of Generated Text
Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "arXiv — non-exclusive license to distribute" does not allow redistributing the text itself. Original — arxiv.org/pdf/1906.04043
Summary
Large language models such as GPT-2 can produce text that ordinary readers struggle to tell apart from human writing, which opens the door to fake reviews, comments and news. The authors present GLTR (Giant Language model Test Room), an open-source, publicly deployed visual tool that helps people judge whether a passage was machine-generated. Its premise is that generators usually draw from the high-probability head of a model's distribution (via temperature, top-k or beam search), while humans more often pick unexpected words. Using a detection model (GPT-2 117M or BERT), GLTR scores every token by its probability, its rank among predictions and the entropy of the predicted distribution. It then colors tokens by rank bucket and shows histograms of these scores. On 50 documents from each of six sources, rank-bucket features separated real from fake text far better than a bag-of-words baseline. In a study with 35 NLP students, the overlay raised detection accuracy from about 54% to 72% with no prior training. The work matters because it offers a cheap, explainable forensic aid that non-experts can use.
Key points
- Three statistical tests: word probability, absolute rank of the word and predictive entropy. The default overlay colors tokens by rank: top-10 green, top-100 yellow, top-1,000 red, everything else purple. Hovering over a word shows the model's top-5 alternatives.
- Validation data: three machine sources and three human sources, 50 articles each.
- Machine: GPT-2 1.5B with temperature 0.7, GPT-2 1.5B with top-40 truncation, and the Washington Post Heliograf system.
- Human: children's book corpus (CBT), NYT articles, and Nature/Science abstracts.
- Classifier results (cross-validated AUC): top-k rank buckets reached 0.87 under GPT-2 and 0.85 under BERT. Average probability scored about 0.70–0.71, and the bag-of-words baseline scored 0.63. Human texts used words outside the top 100 predictions 2.41× more often under GPT-2 (1.67× under BERT), even in low-entropy contexts.
- Human-subjects study (35 students): accuracy rose from 54.2% to 72.3%, an average treatment effect of +18.1% (p < 0.001). Participants rated unaided difficulty at 3.89 out of 5. Qualitatively, generated text tends to repeat entity names rather than use pronouns, and Heliograf output shows highly parallel sentence structure.
- Resource: the demo is at gltr.io, and the code is on GitHub (HendrikStrobelt/detecting-fake-text) with an extensible PyTorch backend. In its first month the demo had about 30,000 page views.
Cited by
- Fast-DetectGPT: Efficient Zero-Shot Detection of Machine-Generated Text via Conditional Probability Curvature
- How Close is ChatGPT to Human Experts? Comparison Corpus, Evaluation, and Detection
- Automatic Detection of Generated Text is Easiest when Humans are Fooled
- Paraphrasing evades detectors of AI-generated text, but retrieval is an effective defense
- Can AI-Generated Text be Reliably Detected?
- Release Strategies and the Social Impacts of Language Models
- GLM-130B: An Open Bilingual Pre-trained Model
Cite
@misc{gehrmann2019gltr,
title = {{GLTR: Statistical Detection and Visualization of Generated Text}},
author = {Gehrmann, Sebastian and Strobelt, Hendrik and Rush, Alexander M.},
year = {2019},
doi = {10.48550/arxiv.1906.04043},
eprint = {1906.04043},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.1906.04043}
}References
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