ReFACT: A Benchmark for Scientific Confabulation Detection with Positional Error Annotations

Abstract: LLMs frequently confabulate scientific facts,severely undermining their trustworthiness. Addressing this challenge requires benchmarks that go beyond binary factuality and enable fine-grained evaluation. We introduce \textbf{ReFACT} (\textit{Reddit False And Correct Texts}), a benchmark of 1,001 expert-annotated question--answer pairs spanning diverse scientific domains for the detection of scientific confabulation. Each instance includes both a scientifically correct answer and a non-factual counterpart annotated with \textbf{precise error spans and error-types}. ReFACT enables multi-stage evaluation: (1) confabulation detection, (2) fine-grained error localization, and (3) correction. We benchmark 9 state-of-the-art LLMs, revealing limited performance ($\sim$50\% accuracy). Even top models such as GPT-4o fail to distinguish factual from confabulated scientific answers, raising concerns about the reliability of \textit{LLM-as-judge} evaluation paradigms. Our findings highlight the need for fine-grained, human-validated benchmarks to detect and correct scientific confabulation in domain-specific contexts. Dataset is released on \href{https://github.com/ddz5431/ReFACT}{GitHub}\footnote{We provide the dataset at: https://github.com/ddz5431/ReFACT}.