  We present a study of retrieval-augmented language models (LMs) on long-form
question answering. We analyze how retrieval augmentation impacts different
LMs, by comparing answers generated from models while using the same evidence
documents, and how differing quality of retrieval document set impacts the
answers generated from the same LM. We study various attributes of generated
answers (e.g., fluency, length, variance) with an emphasis on the attribution
of generated long-form answers to in-context evidence documents. We collect
human annotations of answer attribution and evaluate methods for automatically
judging attribution. Our study provides new insights on how retrieval
augmentation impacts long, knowledge-rich text generation of LMs. We further
identify attribution patterns for long text generation and analyze the main
culprits of attribution errors. Together, our analysis reveals how retrieval
augmentation impacts long knowledge-rich text generation and provide directions
for future work.
