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arXiv cs.CL
arXiv cs.CL
6/25/2026
Perfect Detection, Failed Control: The Geometry of Knowing vs. Steering in Language Models

Perfect Detection, Failed Control: The Geometry of Knowing vs. Steering in Language Models

Short summary

Research on Gemma and three other language models shows that detecting hallucinations (perfect AUC=1.0) doesn't enable controlling them—the detection direction sits 83° away from the refusal direction. This detection-intervention gap persists across model families and scales, originating in pretraining. Control in LLMs requires high-dimensional intervention, not single-axis manipulation.

  • Detection and control directions diverge by ~83 degrees in hallucination detection across tested models
  • Detection-intervention gap originates in pretraining, not instruction tuning
  • LLM behavior control is fundamentally high-dimensional, not reducible to single activation directions

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