FActScore: Fine-grained Atomic Evaluation of Factual Precision in Long Form Text Generation
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Evaluating the factuality of long-form text generated by large language models (LMs) is non-trivial because (1) generations often contain a mixture of supported and unsupported pieces of information, making binary judgments of quality inadequate, and (2) human evaluation is time-consuming and costly. In this paper, we introduce FActScore (Factual precision in Atomicity Score), a new evaluation that breaks a generation into a series of atomic facts and computes the percentage of atomic facts supported by a reliable knowledge source. We conduct an extensive human evaluation to obtain FActScores of people biographies generated by several state-of-the-art commercial LMs – InstructGPT, ChatGPT, and the retrieval-augmented PerplexityAI – and report new analysis demonstrating the need for such a fine-grained score (e.g., ChatGPT only achieves 58 an automated model that estimates FActScore, using retrieval and a strong language model, with less than a 2 metric to evaluate 6,500 generations from a new set of 13 recent LMs that would have cost 26K if evaluated by humans, with various findings: GPT-4 and ChatGPT are more factual than public models, and Vicuna and Alpaca are some of the best public models.
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