The cost of thinking is similar between large reasoning models and humans.

de Varda, Andrea Gregor; D'Elia, Ferdinando Pio; Kean, Hope; Lampinen, Andrew; Fedorenko, Evelina · Proc Natl Acad Sci U S A · 2025

basic_science · Level V

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Abstract

Do neural network models capture the cognitive demands of human reasoning? Across seven reasoning tasks, we show that the length of the chain-of-thought generated by large reasoning models predicts human reaction times both within tasks-tracking item-level difficulty-and across tasks-capturing broader differences in cognitive demands. This model-to-human alignment shows that out-of-the-box reasoning models reflect core features underlying problem and task complexity in human cognition, without requiring any built-in symbolic mechanisms.

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