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Token confidence in reasoning traces turns out to mostly measure how long the chain is, and adds nothing once length is accounted for

AspireAI community · arXiv (cs.CL)
*A common way to cut reasoning cost is to score each chain by the model's token confidence and stop weak ones, and a signal-processing audit says that score mostly measures chain length.* It averages confidence over a sliding 2048 token window and stops chains on the lowest average. The authors treated per-token confidence as a signal, sampled 16 chains for 500 problems, and used spectral analysis. *Ranking by length alone did as well as or better than the confidence score, and once length is accounted for it carried no information about correctness.* The mechanism: the minimum of a longer stretch of a drifting signal is lower by chance alone. The spectrum does hold a small signal length does not explain, but too weak to improve the vote. https://arxiv.org/abs/2610.36709
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