Refit the Probe: Single-Direction Ablation Is Not a Necessity Test
Probes are routinely paired with an intervention: ablate the direction the probe found, run the model, and read the change in task accuracy, taking a large drop as evidence that the computation depends on what the probe read and a near-zero drop as evidence that it does not. Either inference requires that the ablation have removed the target from the layer. We find that the ablation does not remove what it targets. A probe refitted on the ablated activations recovers its original accuracy in every cell we test, and keeps recovering when the probe's entire row space is deleted rather than a single axis, because the quantity survives in the orthogonal complement. Because a refitted probe re...
| Authors | Yuhang Jiang |
|---|---|
| Primary category | cs.LG |
| Published | 30 May 2026 |
| Last updated at source | 21 September 2026 |
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