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Think Smart, Not Hard: Difficulty Adaptive Reasoning for Large Audio Language Models

Paper · 2026 · Zhichao Sheng, Shilin Zhou, Chen Gong et al.

Summary

Large Audio Language Models (LALMs) that use chain-of-thought tend to apply the same reasoning depth to every question. They overthink easy items and under-reason on hard ones. Existing fixes either decide only whether to reason or impose fixed length penalties. The authors first compare SFT with GRPO on Qwen2-Audio-7B-Instruct and Qwen2.5-Omni-7B, using the FS and AVQA training sets. They find that GRPO's explicit reasoning helps on medium and hard questions but slightly hurts easy ones. They then propose a length-based reward whose strength depends on how difficult the model itself finds a question. Difficulty is estimated in two ways: GRDR uses rollout group accuracy, and GA²DR uses audio attention entropy. Both reuse quantities already computed during training. On MMAU, MMAU-v0515 and MMAR, the rewards beat plain GRPO while cutting average reasoning length by at least half. This shows that efficiency and accuracy can improve together when reasoning depth tracks difficulty.

Key points

  • Training data: FS, which combines AVQA (36,036 items) with AudioGrounding, VocalSound, TUT2017 and Clotho-AQA, is about twice the size of AVQA. Evaluation uses MMAU-Test-Mini, MMAU-v0515 and MMAR, with Airbench-Foundation also used in the analysis.
  • GRDR: With a rollout group of G = 8, a question counts as easy (γ = 0) at 6 or more correct answers, medium (γ = 0.5) at 3–5, and hard (γ = 1) below 3.
  • GA²DR: Difficulty is measured from the entropy of the last token's attention over audio tokens, averaged across heads and min-max normalized per batch. The final attention layer worked best.
  • Entropy as a difficulty signal: On MMAU-test-mini, accuracy falls from 72.85 to 69.52 as entropy rises across three intervals.
  • Fixed vs. adaptive rewards: Fixed length rewards do beat plain GRPO but still trail the difficulty-adaptive versions. Code is released on GitHub (zcs-hlt).

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Fields, topics and concepts

Cite

Cite as Zhichao Sheng, Shilin Zhou, Chen Gong and Zhenghua Li. 2026. Think Smart, Not Hard: Difficulty Adaptive Reasoning for Large Audio Language Models. Findings of the Association for Computational Linguistics: ACL 2026.

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/2026.findings-acl.1640

@inproceedings{sheng2026think,
  title = {{Think Smart, Not Hard: Difficulty Adaptive Reasoning for Large Audio Language Models}},
  author = {Zhichao Sheng, Shilin Zhou, Chen Gong and Zhenghua Li},
  booktitle = {Findings of the Association for Computational Linguistics: ACL 2026},
  year = {2026},
  doi = {10.18653/v1/2026.findings-acl.1640},
  url = {https://doi.org/10.18653/v1/2026.findings-acl.1640}
}

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