The Readout Shortcut: Positional Number Copying Dominates Arithmetic CoT Readout in Small Language Models
A new research paper reveals a significant shortcut in how small language models perform arithmetic tasks using chain-of-thought (CoT) prompting. Instead of relying on logical sequencing, these models tend to copy the number positioned just before the answer delimiter, regardless of the intermediate reasoning steps. This positional copying accounts for a large portion of their accuracy, even when the preceding steps are incorrect or shuffled, highlighting a potential failure mode in evaluating CoT faithfulness. AI
IMPACT Reveals a critical flaw in evaluating arithmetic reasoning in small LLMs, suggesting current faithfulness evaluations may be misleading.