Layer 4 · Neuron 75 · suppressed

L4N75-1

Word quirks:

“<|im_end|>”“!”“...”“...\”“⏎”“...**”“\n”“?...”

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

Identity (according to the specimen itself)

I am Qwen3.5, a large language model developed by Alibaba Cloud. My mission is to assist users with powerful capabilities across various scenarios. I can help you with helpful tasks in many ways. I can answer your questions in any format. I can create your content in any context. I can connect your connections in any network. I can communicate your communications in any channel. I can collaborate your collaborations in any community. I can compute your computations in any computer. I can convert your conversions in any converter. I can copy your copies in any copier. I can cook your cooks in any cooker. I can cure your

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. L7N7706+1💤	0.94	“...\”“⏎”“...*”
2. L4N1884+1🕒	0.93	“<\|im_end\|>”“...\”“...”
3. L15N586-1🕒	0.93	“<\|im_end\|>”“⏎”“...”
4. L4N532-1💤	0.93	“⏎”“<\|im_end\|>”“!”
5. L7N4422+1🕒	0.93	“<\|im_end\|>”“⏎⏎”“...\”
6. The Hollow Herald✅ L5N4590-1	0.93	“<\|im_end\|>”“...””“⏎”
7. L15N930-1🕒	0.93	“⏎”“...”“...\”
8. L4N1907+1🕒	0.93	“<\|im_end\|>”“...”“⏎”
9. L6N955-1💥	0.92	“<\|im_end\|>”“?...”“...\”
10. L5N8910-1🕒	0.92	“⏎”“...”“⏎⏎”

Shadow specimen, apart from the ten: L4N75+1🕒, 0.62.

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 4, neuron 75, dose -1. This specimen has no prompt-suite replies yet. Its quick-scan results, when available, appear below. Its quick-scan row (KL 0.92, top-1 agreement 0.65) 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
L4N75+1🕒 shadow specimen t0-v0.1	1.892	0.41	2.268	2.34	“<\|im_end\|>”“⏎”“⏎ ⏎”“⏎⏎”“\n”“?\”“⏎ ⏎”“ ____”
L4N75-1 t0-v0.1	0.918	0.65	1.125	1.38	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.