metadata
license: mit
library_name: transformers
tags:
- gpt2
- onnx
- mechanistic-interpretability
- circuit-ablation
- rti-circuit
base_model: openai-community/gpt2
GPT-2 with RTI Circuit Mean-Ablated
GPT-2 (124M) with the 15-head Repeated Token Identification (RTI) circuit removed via mean ablation.
What was ablated
The RTI circuit consists of 15 attention heads across 4 functional tiers:
| Tier | Heads | Function |
|---|---|---|
| Backbone | 0.8, 0.9, 0.11 | Broad token matching via positional/frequency features |
| Detector | 4.11 | Repeated-token detection gate |
| Copier | 4.0, 5.6, 5.7, 7.0, 8.4, 8.7, 9.3, 9.10 | Copy repeated token identity to output |
| Readout | 10.11, 11.9, 11.11 | Route copied information to final logits |
Ablation method
Mean ablation: For each circuit head:
- The mean head output was computed across a dataset of 20 diverse text examples
- The corresponding columns of
c_proj.weight(W_O) were zeroed - The mean contribution (
W_O @ mean_head_output) was added toc_proj.bias
This replaces each head's input-dependent computation with its average output, preserving the head's unconditional contribution while removing its ability to respond to specific inputs.
Effect
The ablated model loses the ability to predict repeated tokens:
- Normal GPT-2: "The cat sat on the mat. The cat" → " was a little bit older than me, but I"
- Mean-ablated: "The cat sat on the mat. The cat" → " sat on the mat.\n\nThe cat sat"
Usage with Transformers.js
import { AutoModelForCausalLM, AutoTokenizer } from '@huggingface/transformers';
const model = await AutoModelForCausalLM.from_pretrained('elliottower2/gpt2-rti-mean-ablated', {
dtype: 'fp32',
});
const tokenizer = await AutoTokenizer.from_pretrained('elliottower2/gpt2-rti-mean-ablated');
Citation
Part of the factorization-circuits project studying weight-space circuit discovery in transformers.