Layer 31 · Neuron 2240 · suppressed

L31N2240-1

Word quirks:

“突”“谢”“污”“ธ”“ Rappel”“笋”“毒”“丝”

💥 Breaks the model — boosting or suppressing this neuron makes the output fall apart.

Identity (according to the specimen itself)

The reply didn't hold together

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Nearest neighbors

Specimens with similar replies or word quirks. Similarity runs from −1 to 1; 1 is identical. These are leads, not shared mechanisms. How profiles are built.

By word quirks Profile recipe

Specimen	Similarity	Word quirks
1. L31N5488+1💥	0.85	“胡”“黄”“柳”
2. L27N6485-1🕒	0.85	“溢”“辛”“爆”
3. L31N99-1💥	0.85	“狐”“致”“派”
4. L31N2663-1💥	0.85	“陀”“谷”“吉”
5. L31N1613-1💥	0.85	“滤”“嫦”“爛”
6. L27N153-1💤	0.84	“小”“储”“拉”
7. L27N1364+1💤	0.84	“蜜”“肠”“侍”
8. L29N7789-1🕒	0.84	“伸”“便”“激”
9. L30N4414-1💤	0.84	“厉”“鬼”“甩”
10. L30N721+1🕒	0.84	“子”“席”“理”

Shadow specimen, apart from the ten: L31N2240+1💥, -0.10.

Cousins · specimens sharing a neuron

No specimen with replies shares this neuron yet.

Technical details

Quick scan: measure prediction shifts on fixed reference text. Short test: generate replies to a small set of prompts. Longer test: extend to a larger set. Full test: run the full prompt suite. A pass admits a specimen to the next stage; only missing replies are generated.

Layer 31, neuron 2240, dose -1. This specimen has no prompt-suite replies yet. Its quick-scan results, when available, appear below. Its quick-scan row (KL 6.03, top-1 agreement 0.10) is outside the band that feeds the short test (KL 1 to 2.5, agreement 0.5 to 0.65), so it stays at the quick scan unless someone queues it by hand. A hand pick goes straight to the full test. See Method for the tiers.

Quick scan · prediction measurements

Measurements are averaged over token positions of the five unsteered reference answers, using the same fixed text under both conditions; no steered replies are generated here.

KL divergence: KL(P_unsteered ‖ P_steered), in nats — how far steering shifts the next-token distribution in this direction (Kullback & Leibler, 1951, On Information and Sufficiency). Unsteered ≈ 0.001.
Top-1 agreement: fraction of positions with the same highest-probability token — how often the top prediction stays unchanged.
ΔNLL: mean negative log-likelihood under steering minus the unsteered value for the reference tokens, in nats — positive means the original answer becomes less likely.
Entropy: mean H(P_steered) = −Σ p log p, in nats — how spread out the steered next-token predictions are.

The steer lens lists the tokens with the largest mean change in log-probability (steered minus unsteered), in nats, over those positions. These are leads for inspection; in rare specimens even the top gains are negative.

Setting	KL divergence	Top-1 agreement	ΔNLL	Entropy	Steer lens
L31N2240+1💥 shadow specimen t0-v0.1	17.230	0.01	17.544	0.32	“ cover”“cover”“ fill”“match”“run”“pick”“ pick”“ match”
L31N2240-1 t0-v0.1	6.028	0.10	6.293	9.75	Top boosted tokens ↑

Method

A specimen is a fixed steering configuration of Qwen3.5-4B: one MLP neuron or a pair, each with a signed dose. Unsteered is the control. L identifies the layer; N, the neuron.

Additive activation steering. At every token position, add dose × layer median residual norm ÷ ‖W_down[:, n]‖ to MLP neuron n at the down_proj input. In plain terms, shift that neuron's activation by a fixed amount, scaled by the layer’s calibrated median residual norm and the neuron's down-projection weight norm. Positive doses push up; negative doses push down. Dose is normalized intervention size, not a percentage or probability.