SHAPE of Chain-of-Thought in Math Reasoning

Hugging Face Daily Papers Papers

Summary

SHAPE is a framework that analyzes chain-of-thought reasoning in large language models using semantic spaces and heuristics to diagnose and improve mathematical reasoning through post-training.

Large language models (LLMs) achieve strong performance on mathematical reasoning benchmarks, yet the mathematically meaningful skills underlying their reasoning remain underexplored. We introduce SHAPE, a framework that analyzes Chain-of-Thought (CoT) trajectories through two lenses developed in mathematics education: (1) semantic spaces: the model's evolving mathematical interpretations of a problem (e.g., algebraic, geometric), and (2) heuristics: the specific mathematical actions taken within those spaces (e.g., simplifying the problem, working backward). We first use SHAPE to analyze the reasoning patterns of various models. Our findings reveal that the mathematical heuristics employed by a model better explain final answer correctness than traditional CoT features. Furthermore, models are likely to reach correct solutions by concentrating their reasoning effort within a few semantic spaces rather than exploring many disparate ones -- a pattern consistent with human behavior. Next, we utilize the SHAPE lens to evaluate whether post-training truly enhances mathematical proficiency. We find that reinforcement learning induces mode-seeking in heuristic usage. Lastly, we post-train LLMs by promoting diverse heuristics and demonstrate its effectiveness in improving accuracy. Overall, SHAPE provides a theoretically-grounded diagnostic framework for decoding LLM reasoning and offers a new path toward post-training LLMs for math reasoning. The code for our model is available at https://github.com/holi-lab/SHAPE-of-CoT
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Paper page - SHAPE of Chain-of-Thought in Math Reasoning

Source: https://huggingface.co/papers/2608.28600

Abstract

SHAPE analyzes chain-of-thought reasoning via semantic spaces and heuristics to diagnose LLM mathematical reasoning and improve post-training.

Large language models (LLMs) achieve strong performance on mathematical reasoning benchmarks, yet the mathematically meaningful skills underlying their reasoning remain underexplored. We introduce SHAPE, a framework that analyzesChain-of-Thought(CoT) trajectories through two lenses developed in mathematics education: (1)semantic spaces: the model’s evolving mathematical interpretations of a problem (e.g., algebraic, geometric), and (2)heuristics: the specific mathematical actions taken within those spaces (e.g., simplifying the problem, working backward). We first use SHAPE to analyze the reasoning patterns of various models. Our findings reveal that the mathematicalheuristicsemployed by a model better explain final answer correctness than traditional CoT features. Furthermore, models are likely to reach correct solutions by concentrating their reasoning effort within a fewsemantic spacesrather than exploring many disparate ones -- a pattern consistent with human behavior. Next, we utilize the SHAPE lens to evaluate whetherpost-trainingtruly enhances mathematical proficiency. We find thatreinforcement learninginducesmode-seekingin heuristic usage. Lastly, we post-train LLMs by promoting diverseheuristicsand demonstrate its effectiveness in improving accuracy. Overall, SHAPE provides a theoretically-grounded diagnostic framework for decoding LLM reasoning and offers a new path towardpost-trainingLLMs for math reasoning. The code for our model is available at https://github.com/holi-lab/SHAPE-of-CoT

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