Corrective RAG with Iterative Evidence Verification and Query Reformulation for Scientific Fact Checking
Keywords:
Scientific Fact Checking, Corrective RAG, Iterative Retrieval, Query Reformulation, Evidence Verification, Scifact, Calibrated Gating, Reciprocal Rank FusionAbstract
Scientific claim verification requires a system to retrieve relevant literature, identify evidentiary sentences, and assign a SUPPORT, CONTRADICT, or not-enough-information (NEI) label. A single retrieval pass is inexpensive but leaves recoverable evidence outside the candidate set, whereas unconditional iterative retrieval increases cost and can introduce query drift. This study presents a corrective retrieval-augmented verification pipeline that couples stemmed BM25 retrieval, evidence sentence ranking, a calibrated verifier agent, training-fold evidence memory, query reformulation, and reciprocal-rank fusion. The corrective gate is calibrated inside each training fold. It initiates a second retrieval pass only for low-confidence or weak-evidence cases, accepts a changed label only when the second verifier provides a calibrated confidence gain, and preserves a previously evidence-backed label when the second pass returns NEI. Experiments use the SciFact corpus of 5,183 abstracts and 1,109 labeled claims under the provided five-fold partition. The second pass raises document Recall@5 from 90.3% to 92.8%. The gated system invokes that pass for 17.0% of claims, reaches 68.4% accuracy, 0.656 Macro-F1, and the highest evidence-conditioned joint score of 0.597. Compared with always applying two passes, it improves accuracy by 4.78 points and Macro-F1 by 5.51 points while reducing processed tokens by 41.8%. The results show that iterative retrieval is most effective when evidence accumulation, label replacement, and cost are governed by separate verification decisions.
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