  Hallucination plagues even frontier LLMs--but how bad is it really for
summarizing academic papers? We evaluate Factored Verification, a simple
automated method for detecting hallucinations in abstractive summaries. This
method sets a new SotA on hallucination detection in the summarization task of
the HaluEval benchmark, achieving 76.2% accuracy. We then use this method to
estimate how often language models hallucinate when summarizing across multiple
academic papers and find 0.62 hallucinations in the average ChatGPT (16k)
summary, 0.84 for GPT-4, and 1.55 for Claude 2. We ask models to self-correct
using Factored Critiques and find that this lowers the number of hallucinations
to 0.49 for ChatGPT, 0.46 for GPT-4, and 0.95 for Claude 2. The hallucinations
we find are often subtle, so we advise caution when using models to synthesize
academic papers.
