HEAR Who Said What: Unlocking Speaker-Attributed Reasoning via Counterfactual Voice Grounding

Dongwook Lee, Sangkwon Park, Eunwoo Song, Che Hyun Lee, Youngho Cho, Junho Kim, June Young Yi, Heeseung Kim, Sungroh Yoon


Abstract
Speech Language Models (SLMs) are increasingly deployed in multi-speaker environments, yet their ability to attribute speech to the correct speaker and reason over speaker identities remains unclear. Hence, we introduce **HEAR**, a conceptually hierarchical benchmark diagnosing the foundational capabilities of speaker-attributed reasoning, comprising 2.4K human-verified samples from 887 diverse multi-party audio clips. Evaluating 20 leading SLMs on HEAR reveals they struggle with these foundational tasks, often relying on semantic priors rather than actual vocal cues. To address this, we present **A2R**, a 30B model optimized on *Counterfactual Audio with Speaker-level Hard negatives* (**CASH**), a dataset designed to guide the model to prioritize acoustic vocal cues over linguistic signals. A2R achieves strong performance on HEAR and exhibits zero-shot generalization to diverse multi-speaker downstream tasks, demonstrating that learned speaker attribution unlocks the model’s latent capacity for speaker-aware reasoning. All resources are available on our https://attributetoreason.github.io/AttributeToReason/
Anthology ID:
2026.emnlp-main.2503
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:
56905–56932
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2503/
DOI:
Bibkey:
Cite (ACL):
Dongwook Lee, Sangkwon Park, Eunwoo Song, Che Hyun Lee, Youngho Cho, Junho Kim, June Young Yi, Heeseung Kim, and Sungroh Yoon. 2026. HEAR Who Said What: Unlocking Speaker-Attributed Reasoning via Counterfactual Voice Grounding. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 56905–56932, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
HEAR Who Said What: Unlocking Speaker-Attributed Reasoning via Counterfactual Voice Grounding (Lee et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2503.pdf