Test-Time Adaptation Induces Stronger Accuracy and Agreement-on-the-Line
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Abstract (arXiv)
Recently, Miller et al. (2021) and Baek et al. (2022) empirically demonstrated strong linear correlations between in-distribution (ID) versus out-of-distribution (OOD) accuracy and agreement. These trends, coined accuracy-on-the-line (ACL) and agreement-on-the-line (AGL), enable OOD model selection and performance estimation without labeled data. However, these phenomena also break for certain shifts, such as CIFAR10-C Gaussian Noise, posing a critical bottleneck. In this paper, we make a key finding that recent test-time adaptation (TTA) methods not only improve OOD performance, but drastically strengthen the ACL and AGL trends in models, even in shifts where models showed very weak correlations before. To analyze this, we revisit the theoretical conditions from Miller et al. (2021) that outline the types of distribution shifts needed for perfect ACL in linear models. Surprisingly, these conditions are satisfied after applying TTA to deep models in the penultimate feature embedding space. In particular, TTA causes the data distribution to collapse complex shifts into those can be expressed by a singular scaling variable in the feature space. Our results show that by combining TTA with AGL-based estimation methods, we can estimate the OOD performance of models with high precision for a broader set of distribution shifts. This lends us a simple system for selecting the best hyperparameters and adaptation strategy without any OOD labeled data.
Key facts. Cited by 11 papers in the map (data through 14 Oct 2026). Builds on 52 of its 61 references that are in the map. First posted on arXiv 7 Oct 2023.
Builds on
52 of 61 references.
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Citing papers per year: 2024: 3; 2025: 5; 2026: 3.
11 papers.
- 2024The Entropy Enigma: Success and Failure of Entropy Minimizationcited by 24
- 2024TAPT: Test-Time Adversarial Prompt Tuning for Robust Inference in Vision-Language Modelscited by 23
- 2025Monitoring Risks in Test-Time Adaptationcited by 11
- 2024Accuracy on the wrong line: On the pitfalls of noisy data for out-of-distribution generalisationcited by 9
- 2025Less Data Less Tokens: Multilingual Unification Learning for Efficient Test-Time Reasoning in LLMscited by 3
- 2025Focus on Likely Classes for Test-Time Predictioncited by 1
- 2026When is Test-Time Adaptation Identifiable From Unlabeled Evidence?cited by 1
- 2025Higher-Order Asymptotics of Test-Time Adaptation for Batch Normalization Statisticscited by 0
- 2025Data Curation Matters: Model Collapse and Spurious Shift Performance Prediction from Training on Uncurated Text Embeddingscited by 0
- 2026Autonomous Drift Learning in Data Streams: A Unified Perspectivecited by 0
- 2026Entropy Minimization without Model Collapse: Mitigating Prediction Bias in Medical Imagingcited by 0
- 2026When is Test-Time Adaptation Identifiable From Unlabeled Evidence?10 Sep 2026
- 2026Entropy Minimization without Model Collapse: Mitigating Prediction Bias in Medical Imaging1 Jun 2026
- 2026Autonomous Drift Learning in Data Streams: A Unified Perspective2 May 2026
- 2025Monitoring Risks in Test-Time Adaptation11 Jul 2025
- 2025Less Data Less Tokens: Multilingual Unification Learning for Efficient Test-Time Reasoning in LLMs23 Jun 2025
- 2025Data Curation Matters: Model Collapse and Spurious Shift Performance Prediction from Training on Uncurated Text Embeddings22 Jun 2025
- 2025Higher-Order Asymptotics of Test-Time Adaptation for Batch Normalization Statistics22 May 2025
- 2025Focus on Likely Classes for Test-Time Prediction2 May 2025
- 2024TAPT: Test-Time Adversarial Prompt Tuning for Robust Inference in Vision-Language Models20 Nov 2024
- 2024Accuracy on the wrong line: On the pitfalls of noisy data for out-of-distribution generalisation27 Jun 2024
- 2024The Entropy Enigma: Success and Failure of Entropy Minimization8 May 2024