RationalRewards: Reasoning Rewards Scale Visual Generation Both Training and Test Time

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Main Authors: Wang, Haozhe, Wei, Cong, Ren, Weiming, Liu, Jiaming, Lin, Fangzhen, Chen, Wenhu
Format: Preprint
Published: 2026
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author Wang, Haozhe
Wei, Cong
Ren, Weiming
Liu, Jiaming
Lin, Fangzhen
Chen, Wenhu
author_facet Wang, Haozhe
Wei, Cong
Ren, Weiming
Liu, Jiaming
Lin, Fangzhen
Chen, Wenhu
contents Most reward models for visual generation reduce rich human judgments to a single unexplained score, discarding the reasoning that underlies preference. We show that teaching reward models to produce explicit, multi-dimensional critiques before scoring transforms them from passive evaluators into active optimization tools, improving generators in two complementary ways: at training time, structured rationales provide interpretable, fine-grained rewards for reinforcement learning; at test time, a Generate-Critique-Refine loop turns critiques into targeted prompt revisions that improve outputs without any parameter updates. To train such a reward model without costly rationale annotations, we introduce Preference-Anchored Rationalization (PARROT), a principled framework that recovers high-quality rationales from readily available preference data through anchored generation, consistency filtering, and distillation. The resulting model, RationalRewards (8B), achieves state-of-the-art preference prediction among open-source reward models, competitive with Gemini-2.5-Pro, while using 10-20x less training data than comparable baselines. As an RL reward, it consistently improves text-to-image and image-editing generators beyond scalar alternatives. Most strikingly, its test-time critique-and-refine loop matches or exceeds RL-based fine-tuning on several benchmarks, suggesting that structured reasoning can unlock latent capabilities in existing generators that suboptimal prompts fail to elicit.
format Preprint
id arxiv_https___arxiv_org_abs_2604_11626
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle RationalRewards: Reasoning Rewards Scale Visual Generation Both Training and Test Time
Wang, Haozhe
Wei, Cong
Ren, Weiming
Liu, Jiaming
Lin, Fangzhen
Chen, Wenhu
Artificial Intelligence
Machine Learning
Most reward models for visual generation reduce rich human judgments to a single unexplained score, discarding the reasoning that underlies preference. We show that teaching reward models to produce explicit, multi-dimensional critiques before scoring transforms them from passive evaluators into active optimization tools, improving generators in two complementary ways: at training time, structured rationales provide interpretable, fine-grained rewards for reinforcement learning; at test time, a Generate-Critique-Refine loop turns critiques into targeted prompt revisions that improve outputs without any parameter updates. To train such a reward model without costly rationale annotations, we introduce Preference-Anchored Rationalization (PARROT), a principled framework that recovers high-quality rationales from readily available preference data through anchored generation, consistency filtering, and distillation. The resulting model, RationalRewards (8B), achieves state-of-the-art preference prediction among open-source reward models, competitive with Gemini-2.5-Pro, while using 10-20x less training data than comparable baselines. As an RL reward, it consistently improves text-to-image and image-editing generators beyond scalar alternatives. Most strikingly, its test-time critique-and-refine loop matches or exceeds RL-based fine-tuning on several benchmarks, suggesting that structured reasoning can unlock latent capabilities in existing generators that suboptimal prompts fail to elicit.
title RationalRewards: Reasoning Rewards Scale Visual Generation Both Training and Test Time
topic Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2604.11626