Layer 21 · Neuron 1490 · boosted

L21N1490+1

Word quirks:

“上好”“ propagate”“ Personal”“立于”“ participate”

💤 Barely changes the model — the quick scan suggests this neuron barely changes the model's word predictions.

Identity (according to the specimen itself)

Not asked yet

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. L27N8627+1🕒	0.56	“与”“_and”“and”“-and”“吊”
2. L27N7476-1🕒	0.56	“-and”“和鼓励”“_and”“調”“ pa”
3. L24N1018-1🕒	0.54	“及”“及对”“ and”“及其”“and”
4. L24N519+1🕒	0.53	“并及时”“并提供”“并对”“并从”
5. L27N6444+1🕒	0.53	“及”“及管理”“及技术”“及び”“及对”
6. L31N6054+1💥	0.53	“与研究”“与实践”“与”“与管理”“与治疗”
7. L18N2574+1💤	0.53	“方式和”“部门和”“*j”“油和”“中心和”
8. L23N5219-1💤	0.53	“和新”“ and”“&T”“和教育”“ и”
9. L28N2382-1🕒	0.53	“跟”“跟她”“跟我们”“&E”
10. L27N4747+1🕒	0.52	“ and”“and”“和操作”“以及”“和处理”

Shadow specimen, apart from the ten: L21N1490-1💤, 0.36.

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 21, neuron 1490, dose +1. This specimen has no prompt-suite replies yet. Its quick-scan results, when available, appear below. Its quick-scan row (KL 0.71, top-1 agreement 0.71) 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
L21N1490+1 t0-v0.1	0.708	0.71	0.748	1.40	Top boosted tokens ↑
L21N1490-1💤 shadow specimen t0-v0.1	0.629	0.72	0.762	1.19	“条件和”“条件下的”“ vist”“预计”“不倒”

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.