steering-block-selection

name

steering-block-selection

description

How to choose where (and how many sites) to intervene for any operation on internal representations — activation patching, steering, CAA, DAS, SAE feature scaling, attribution patching. Use whenever the plan declares a target block / layer / site, especially when it hard-codes a single index (`target_block: 4`, `layer: 16`) without justification or copied from another paper. Covers picking the site by screening (gradient / attribution, or an activation signal) and by heuristic (mid-to-late layers usually steer best; widen to 3–5 layers if one is inert; sweep the stack at spaced intervals), and which component to target (attention / MLP / residual stream — circuit discovery studies attention heads + MLP). Prevents two symmetric failures: too few sites → downstream norm/attention denoise it → false "no effect"; too many → off-distribution collapse and the localization claim becomes untestable. Triggers include `target_block = 4`, `sliding window = 15`, `layer ∈ [12,18]`, `early blocks (0-7)`, "steering had no effect" while the same coefficient at a window did.

Steering Block / Layer Selection

The point

Where and how many sites you intervene on changes both the effective strength of the intervention and whether a localization claim is testable.

• Too few (single site on a deep stack) → downstream norm/attention denoise it → looks like "no effect".
• Too many (whole stack) → off-distribution collapse → the effect is collapse-driven and no longer localized.

Choosing where to intervene

Pick the site(s) by a screening method, by heuristic, or both.

By method (pre-screen the layers):

• Gradient-based — rank layers by gradient / attribution score w.r.t. the target.
• Activation-based — rank by an activation signal (probe accuracy, diff-mean magnitude, separability).

By heuristic:

1. Mid-to-late layers usually work best — start there.