Rethinking the Role of Proxy Rewards in Language Model Alignment
This work addresses the challenge of reliable and interpretable reward modeling for LLM alignment, offering a simpler baseline that could reduce reliance on human feedback, though it is incremental in improving existing proxy reward methods.
The paper tackles the problem of aligning Large Language Models with human values by developing a white-box reward function that replicates ground truth rewards without needing explicit human feedback datasets, achieving competitive performance with strong open-source reward models in alignment benchmarks.
Learning from human feedback via proxy reward modeling has been studied to align Large Language Models (LLMs) with human values. However, achieving reliable training through that proxy reward model (RM) is not a trivial problem, and its behavior remained as a black-box. In this paper, we study the role of proxy rewards in the LLM alignment via `reverse reward engineering' by composing interpretable features as a white-box reward function. We aim to replicate the ground truth (gold) reward signal by achieving a monotonic relationship between the proxy and gold reward signals after training the model using the proxy reward in reinforcement learning (RL). Our findings indicate that successfully emulating the gold reward requires generating responses that are relevant with enough length to open-ended questions, while also ensuring response consistency in closed-ended questions. Furthermore, resulting models optimizing our devised white-box reward show competitive performances with strong open-source RMs in alignment benchmarks. We highlight its potential usage as a simple but strong reward baseline for the LLM alignment, not requiring explicit human feedback dataset and RM training. Our code is available at https://github.com/naver-ai/rethinking-proxy-reward.