  The remarkable abilities of large language models (LLMs) like GPT-4 partially
stem from post-training processes like Reinforcement Learning from Human
Feedback (RLHF) involving human preferences encoded in a reward model. However,
these reward models (RMs) often lack direct knowledge of why, or under what
principles, the preferences annotations were made. In this study, we identify
principles that guide RMs to better align with human preferences, and then
develop an axiomatic framework to generate a rich variety of preference signals
to uphold them. We use these axiomatic signals to train a model for scoring
answers to longform questions. Our approach yields a Preference Model with only
about 220M parameters that agrees with gold human-annotated preference labels
more often than GPT-4. The contributions of this work include: training a
standalone preference model that can score human- and LLM-generated answers on
the same scale; developing an axiomatic framework for generating training data
pairs tailored to certain principles; and showing that a small amount of
axiomatic signals can help small models outperform GPT-4 in preference scoring.
We release our model on huggingface:
https://huggingface.co/corbyrosset/axiomatic_preference_model
