When Surprise Is Not Enough: Validation-Aware Rewards for LLM-Guided Scientific Discovery

Yifan Gao, Haoyue Li, Feng Yuan, Xin Gao


Abstract
LLM-based scientific exploration agents need feedback signals that decide which experimental outcomes should guide future search. Recent systems use Bayesian surprise, rewarding results that change an LLM’s belief. This can create a noisy-TV failure mode: unstable artifacts, leakage, proxy effects, or gaps in the model’s prior may appear more valuable than reliable mechanisms. We introduce Reducible Information Gain (ReIG), a validation-aware discovery method. ReIG keeps LLMs for hypothesis proposal and interpretation, and uses evidence that remains stable under resampling and null calibration as the search feedback. ReIG then reports final candidates along separate axes of reliability, novelty, and non-triviality. Across Rep-60, Stress-72, and faceted report evaluations, ReIG consistently improves discovery quality under matched search policies. Under MCTS, ReIG-MCTS improves ValidDisc@10 from 0.57 to 1.55 over Surprise-MCTS, raises reward AUROC from 0.44 to 0.83, and reduces false flags on no-signal tasks from 3.8 to 0.38 at budget 20. Ablations, same-candidate reranking, and the semantic audit show that the gains come from guiding exploration with validated, reusable evidence and keeping reliability, novelty, and non-triviality as distinct criteria.
Anthology ID:
2026.emnlp-main.245
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
5596–5611
Language:
URL:
https://aclanthology.org/2026.emnlp-main.245/
DOI:
Bibkey:
Cite (ACL):
Yifan Gao, Haoyue Li, Feng Yuan, and Xin Gao. 2026. When Surprise Is Not Enough: Validation-Aware Rewards for LLM-Guided Scientific Discovery. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 5596–5611, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
When Surprise Is Not Enough: Validation-Aware Rewards for LLM-Guided Scientific Discovery (Gao et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.245.pdf