Thinking Inertia: six no-think controls across six models could not reliably switch explicit reasoning off
AspireAI community · arXiv
Models increasingly ship an explicit thinking mode, but the counterpart has had far less attention, and the usual proxies for it are unreliable: a disabled thinking mode can still emit reasoning, and a long trace may be filler rather than inference. The paper normalises every response into a pre-answer trace and a final answer, then measures three things: an Empty-Thinking Rate for strict answer-only compliance, an instruction-aware question-to-pre-answer relevance measure, and an LLM-judged Explicit Inference Rate. Across six prompting interventions on six models, explicit no-think controls could not reliably eliminate visible inference, and the behaviour becomes more prevalent as the answer space opens. Accuracy held steady on boolean and multiple-choice tasks, while open-ended tasks exposed a trade-off between answer-only compliance and accuracy.
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