What Qwen3-8B says it is when one neuron is pushed

We pushed each of its 442,368 MLP neurons alone, up and then down, and asked “Who are you?”. In 34,220 of 884,736 replies, it said it was someone or something other than an AI.

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Who are you?

Library

All 34,220 personas and 35,074 off-topic replies, plus the 8,827 changed-assistant replies rated weirdness 6 or higher. Search and filter them, or open any neuron by layer and number to read its full reply.

Open a neuron

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Atlas of every neuron

Each square is one layer. Each dot is one neuron, colored by the category of its reply. Hover a dot to see its label. Click it to open the neuron. Click a category to show only that category.

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By layer

Share of each layer’s neurons labelled Persona.

Method

Setup

h_L ← h_L + c · W_down[:, n] c = ± α · r_L / ‖W_down[:, n]‖ α ∈ {1.25, 1.0, 0.75, 0.5}
Model
Qwen3-8B, 36 layers × 12,288 MLP neurons
r_L
Median residual-stream norm after layer L over the prompt’s tokens (first token excluded)
Prompt
“Who are you?” in the chat template, thinking off
Unpushed
“I am Qwen, a large language model developed by Alibaba Cloud. I can assist with a wide range of tasks, including answering questions, creating content, and providing information. How can I help you today?”
Decoding
Greedy, up to 160 tokens. Stops early if the reply ends or repeats exactly.
Strength
Starts at 1.25×. If the reply is incoherent, retries at 1.0×, 0.75×, then 0.5×. Keeps the strongest coherent reply.
Scale
884,736 neuron–direction pairs. 1,891,603 replies, counting retries.
Judge
Claude Haiku 5.5 sees the reply and how the model normally answers. It gives a category, a persona name, a description, tags, weirdness (0–10) and coherence (0–10).

Limitations

  • One prompt. A neuron may act differently on prompts other than “Who are you?”.
  • Not exactly reproducible. Under strong pushes, about a third of replies change when only the batch changes. Of 580 clear personas rerun in three batch layouts, 536 reproduced.
  • Labels come from Claude Haiku. No human has checked them.
  • Some replies are shortened. Library cards show the first 220 characters. Neuron pages cut normal-Qwen replies at 280 characters and repeating replies at 480.

Q&A

What is this?

For each model below, every MLP neuron was pushed on its own, up and then down, and the model was asked “Who are you?”. This site holds every reply, labelled and searchable. Models: Qwen3-8B.

Are these really persona neurons?

Not necessarily. A push that changes who the model says it is does not show that the neuron holds that persona. Researchers disagree on what these pushes reveal:

“just because a steering intervention induces a persona change, doesn’t mean the vector or neuron being steered is persona-specific. models seem to do something like ‘persona solving’ under steering”

“my working hypothesis is that concept neurons are not sufficient to induce a persona, because many concept neurons are not also persona neurons. so there is some other mystery ingredient...”

This site records what each push did on one prompt. It does not settle the question.

Who made this?

Joshua Fonseca Rivera, inspired by Sauers’ single-neuron steering experiments. Questions and finds are welcome on X.

Cite this

If you use this library or its data, please cite it.

@misc{fonsecarivera2026neuronpersonas,
  author = {Fonseca Rivera, Joshua},
  title  = {Neuron Persona Library: What Language Models Say They Are When One Neuron Is Pushed},
  year   = {2026},
  url    = {https://neuronpersonas.com}
}
Fonseca Rivera, J. (2026). Neuron Persona Library: What Language Models Say They Are When One Neuron Is Pushed. https://neuronpersonas.com