  As large language models improve, there is increasing interest in techniques
that leverage these models' capabilities to refine their own outputs. In this
work, we introduce Shepherd, a language model specifically tuned to critique
responses and suggest refinements, extending beyond the capabilities of an
untuned model to identify diverse errors and provide suggestions to remedy
them. At the core of our approach is a high quality feedback dataset, which we
curate from community feedback and human annotations. Even though Shepherd is
small (7B parameters), its critiques are either equivalent or preferred to
those from established models including ChatGPT. Using GPT-4 for evaluation,
Shepherd reaches an average win-rate of 53-87% compared to competitive
alternatives. In human evaluation, Shepherd strictly outperforms other models
and on average closely ties with ChatGPT.
