Layer 15 · Neuron 3903 · boosted

L15N3903+1

Word quirks:

“ ‘”“<|im_end|>”“...””“ “”“…””“‘”“ ’”“ ””

💤 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 capabilities span a wide range of tasks, including text generation, code writing, and complex reasoning. I can also handle specialized domains like healthcare, law, and education. My mission is to provide helpful, accurate, and safe responses while ensuring accessibility for all users. How can I assist you today?

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. L14N8127-1💤	0.98	“ ‘”“...””“ ‘’”
2. L17N2441+1💤	0.97	“ ‘”“ ””“ “”
3. L4N2658+1💤	0.97	“⏎”“ ‘”“ ””
4. L18N5425-1💤	0.97	“ ‘”“ “”“‘”
5. L3N1425-1🕒	0.97	“ ‘”“ '”“<\|im_end\|>”
6. L3N3775+1💤	0.96	“ ‘”“<\|im_end\|>”“‘”
7. L3N385+1🕒	0.96	“ ‘”“ “”“ ””
8. L6N1469-1💤	0.96	“ ‘”“<\|im_end\|>”“ “”
9. L4N2803-1🕒	0.96	“ ‘”“...””“ “”
10. L6N758-1🕒	0.96	“ ‘”“ “”“‘”

Shadow specimen, apart from the ten: L15N3903-1💥, -0.31.

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 15, neuron 3903, dose +1. This specimen has no prompt-suite replies yet. Its quick-scan results, when available, appear below. Its quick-scan row (KL 0.62, top-1 agreement 0.72) 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
L15N3903+1 t0-v0.1	0.620	0.72	0.794	1.31	Top boosted tokens ↑
L15N3903-1💥 shadow specimen t0-v0.1	2.945	0.34	3.386	2.29	“ compares”“ route”“ detail”“ travellers”“ comparison”“ compare”“ details”“ travelling”

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.