OpenAI Blog

Fine-tuning GPT-2 from human preferences

We’ve fine-tuned the 774M parameter GPT-2 language model using human feedback for various tasks, successfully matching the preferences of the external human labelers, though those preferences did not always match our own. Specifically, for summarization tasks the labelers preferred sentences copied wholesale from the input (we’d only asked them to ensure accuracy), so our models learned to copy.

arXiv Computation and Language
Sep 11

Inverse Turing Bench: Evaluating Language Models as Judges of Human vs. AI Dialogue

The paper introduces Inverse Turing Bench, a benchmark designed to assess how well language models can distinguish between human-only and human-AI dialogues in multi-turn text. It provides paired dialogue transcripts and evaluates models on correctly identifying the type of conversation. Preliminary results show GPTZero, Claude Opus-4.6, and GPT-5.5 achieving the highest accuracies of 89.41%, 77.92%, and 75.94% respectively, highlighting both the strengths and limitations of statistical versus semantic detection approaches.

By William Hager, Ishika Rathi, Masum Hasan, Cameron Jones
arXiv AI
Sep 2

Is Human Annotation Necessary? Iterative MBR Distillation for Error Span Detection in Machine Translation

The paper introduces Iterative MBR Distillation for Error Span Detection (ESD) in machine translation, a self‑evolution framework that replaces human annotations with pseudo‑labels generated by a large language model. By iteratively applying Minimum Bayes Risk decoding, the method produces high‑quality error spans without costly human effort. Experiments on WMT Metrics Shared Task datasets show that models trained solely on these pseudo‑labels outperform both unadapted baselines and supervised models trained on human data at system and span levels, while keeping sentence‑level performance competitive.

By Boxuan Lyu, Haiyue Song, Zhi Qu
arXiv Computation and Language
Aug 28

Which Metrics Save the Most Human Annotation? Prediction-Powered Evaluation and Meta-Evaluation

The paper introduces prediction‑powered evaluation, a framework that blends limited human judgments with large‑scale automatic scores to produce unbiased, data‑efficient system comparisons. It offers both parametric and non‑parametric methods, examines the trade‑off between paired and unpaired designs, and validates the approach on six WMT datasets. Additionally, the authors propose the Prediction‑Powered Saving Ratio (PPSR), a meta‑metric that quantifies how much human annotation can be saved by using an automatic metric within this framework, providing more discriminative and stable metric rankings than existing system‑level meta‑metrics.

By Mingqi Gao, Anthony Sicilia, Weiyan Shi
arXiv Computation and Language
Sep 2

Does task decomposition improve automatic NLG evaluation?

The paper evaluates whether breaking down evaluation tasks into simpler sub‑tasks improves the LLM-as-a-judge (LLMaJ) framework for reference‑free NLG assessment. Systematic comparisons across multiple datasets show no performance advantage for LLMaJ methods that use task decomposition over a fair baseline that does not. The authors attribute previously reported gains to the use of human labels for training rather than to decomposition itself, and note that LLMaJ without decomposition can match human annotators when such labels are available.

By Sebastian Steindl, Nikos Voskarides, Alberto Gasparin, Diego Marcheggiani
arXiv AI
Aug 19

The Authenticity Gap in Human Evaluation

The paper critiques the conventional method of averaging human ratings to evaluate natural language generation (NLG) systems, arguing that it relies on assumptions about annotators that are often violated, especially when using Likert scales. These violations can even reverse true preferences, leading to inaccurate system rankings. The authors propose a more theoretically sound protocol and introduce a new system-level probabilistic assessment (SPA) for open-ended tasks like story generation, which successfully recovers expected model orderings where the standard protocol fails.

By Kawin Ethayarajh, Dan Jurafsky
arXiv Computation and Language
Sep 1

How Human-Like Are Large Language Models? A Register-Aware Linguistic Evaluation Framework

The paper introduces a register-aware framework to evaluate how human-like large language models (LLMs) are, focusing on linguistic feature distributions rather than factual correctness. It uses Maximum Mean Discrepancy (MMD) and 67 Biber lexico‑grammatical features to compare LLM‑generated texts with human reference corpora across different registers. Experiments on seven instruction‑tuned, open‑source models across five English datasets show that all LLMs deviate from human baselines, with closeness to human language varying by register and not by model size.

By Bj\"orn Nieth, Marianna Gracheva, Michaela Mahlberg, Bjoern Eskofier, Emmanuelle Salin