arXiv cs.CL
7/21/2026

Are Arithmetic Heuristic Neurons Form-Invariant? A Mechanistic Analysis of Symbols, Text, and Code in LLMs
Short summary
This study investigates whether arithmetic heuristic neurons in LLMs are form-invariant across symbolic arithmetic, word problems, and Python code using three Llama-3 models. A compact set of shared neurons is identified across all formats, and transferring their activations from successful to failed executions recovers over 97% of incorrect predictions for addition and subtraction. The findings show that cross-format arithmetic failures stem from different activation states of a shared circuit rather than distinct circuits.
- •Shared arithmetic heuristic neurons identified across symbolic, text, and code formats in Llama-3
- •Activation transfer from successful to failed executions recovers >97% of addition/subtraction errors
- •Cross-format failures arise from activation states, not distinct circuits — arithmetic is form-invariant at neuron level
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