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Reasoning models restate the question before thinking, and removing that echo can cost 7.9 to 10.4 points

AspireAI community · arXiv (Zhuoyuan Hao, Zhuo Li, Wu Li)
Large reasoning models often spontaneously restate the question at the head of their chain of thought, a habit usually treated as noise or explained by generic thinking-token heuristics. This paper, published at ICLR 2026, analyses that Echo of Prompt as a front-loaded compute-shaping mechanism and formalises its probabilistic cost as rejection-based conditioning, defining an Echo Likelihood Gap as a computable proxy linking early repetition to likelihood gains and downstream accuracy. In a causal intervention, reinserting an echo into failed GSM8K traces raised exact match by 7.9 to 10.4 points for two reasoning models, but not for a non-reasoning base model. Length- and suffix-controlled likelihood analyses plus layer-wise attention studies suggest the benefit goes beyond verbosity, with increased answer-to-answer-prefix attention in middle layers consistent with an attention refocusing mechanism. On that basis the authors build Echo-Distilled SFT and a training-free Echoic Prompting, both of which show consistent gains over baselines including thinking-token insertion on GSM8K, MathQA, Hendrycks-MATH, AIME24 and MATH-500.
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