Language Models Can Learn from Verbal Feedback Without Scalar Rewards
Authors: name: Renjie Luo; name: Zichen Liu; name: Xiangyan Liu; name: Chao Du; name: Min Lin; name: Wenhu Chen; name: Wei Lu; name: Tianyu Pang
Published: 2025-09-26 17:58:27

Abstract: LLMs are often trained with RL from human or AI feedback, yet such methods
typically compress nuanced feedback into scalar rewards, discarding much of
their richness and inducing scale imbalance. We propose treating verbal
feedback as a conditioning signal. Inspired by language priors in text-to-image
generation, which enable novel outputs from unseen prompts, we introduce the
feedback-conditional policy (FCP). FCP learns directly from response-feedback
pairs, approximating the feedback-conditional posterior through maximum
likelihood training on offline data. We further develop an online bootstrapping
stage where the policy generates under positive conditions and receives fresh
feedback to refine itself. This reframes feedback-driven learning as
conditional generation rather than reward optimization, offering a more
expressive way for LLMs to directly learn from verbal feedback. Our code is
available at https://github.com/sail-sg/feedback-conditional-policy.