In language model alignment, the effectiveness of reinforcement learning from human feedback (RLHF) hinges on the excellence of the underlying reward model. A pivotal concern is ensuring the high quality of this reward model, as it significantly influences the success of RLHF applications. The challenge lies in developing a reward model that accurately reflects human preferences, a critical factor in achieving optimal performance and alignment in language models.
Recent advancements in large language models (LLMs) have been facilitated by aligning their behavior with human values. RLHF, a prevalent strategy, guides models toward preferred outputs by defining a nuanced loss function reflecting subjective text quality. However, accurately modeling human preferences involves costly data collection. The quality of preference models depends on feedback quantity, response distribution, and label accuracy.
The researchers from ETH Zurich, Max Planck Institute for Intelligent Systems, Tubingen, and Google Research have introduced West-of-N: Synthetic Preference Generation for Improved Reward Modeling, a novel method to enhance reward model quality by incorporating synthetic preference data into the training dataset. Building on the success of Best-of-N sampling strategies in language model training, they extend this approach to reward model training. The proposed self-training strategy generates preference pairs by selecting the best and worst candidates from response pools to specific queries.
The proposed West-of-N method generates synthetic preference data by selecting the best and worst responses to a given query from the language model’s policy. Inspired by Best-of-N sampling strategies, this self-training strategy significantly enhances reward model performance, comparable to the impact of incorporating a similar quantity of human preference data. The approach is detailed in Algorithm 1, which includes a theoretical guarantee of correct labeling for generated preference pairs. Filtering steps based on model confidence and response distribution further enhance the quality of the generated data.
The study evaluates the West-of-N synthetic preference data generation method on the Reddit TL;DR summarization and Anthropic Helpful and Harmless dialogue datasets. Results indicate that West-of-N significantly enhances reward model performance, surpassing gains from additional human feedback data and outperforming other synthetic preference generation methods such as RLAIF and RLCD. West-of-N consistently improves model accuracy, Best-of-N sampling, and RL-finetuning across different base preference types, demonstrating its effectiveness in language model alignment.
To conclude, The researchers from Google Research and other institutions have proposed an effective strategy, West-of-N, to enhance reward model (RM) performance in RLHF. Experimental results showcase the method’s efficacy across diverse initial preference data and datasets. The study highlights the potential of Best-of-N sampling and semi-supervised learning for preference modeling. They further suggested further exploring methods like noisy student training to elevate RM performance in conjunction with West-of-N.
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