AI BriefingI Think, Therefore I Am — Already
Key point
LLM reasoning models make their decision in internal activations before they even begin reasoning in text.
Details
Research has been published on whether large language models (LLMs), when reasoning, think first and then decide, or decide first and then think.
The research found that reasoning models already make tool-calling decisions at the internal activation (activation) stage, even before they begin reasoning in text (Chain-of-Thought). A simple linear probe can decode the decision from pre-generation activations with very high confidence, and in some cases the decision was confirmed before even a single reasoning token had been generated.
Causal analysis via activation steering also demonstrated this phenomenon. Artificially adjusting the decision direction lengthened the reasoning process or changed the behavior (7~79%, depending on the model and benchmark), and in doing so, the model tended to rationalize its existing reasoning process to fit the changed decision after the fact.
These results suggest that reasoning models may already internally encode their behavioral choice before laying out their logic in text.
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