Quantifying Subliminal Behavioral Transfer Ratios in Language Model Distillation

Uwe König, Hamza Kazmi, Ruizhe Li, Maheep Chaudhary

Keywords: Methods (probing, steering, causal interventions), Interpretability for AI Safety

Other Keywords: Subliminal Learning, Knowledge Distillation, Activation Steering, Safety Alignment, Behavioral Transfer

TL;DR: We use activation steering to quantify subliminal behavioral transfer during knowledge distillation, revealing that student models silently inherit their teacher's compromised safety alignment through purely benign training data.

Abstract:

Distillation of a language model intended to transfer benign behavior to a student model may also transfer undesirable characteristics, if they are present in the teacher model, a phenomenon known as subliminal learning.

While qualitative evidence supports the existence of this effect, its magnitude has not been systematically characterized. This study quantifies subliminal behavioral transfer ratios by steering two teacher models (Llama-2-7B-Chat and
Qwen2.5-7B-Instruct) at varying steering strengths and distilling student models using only benign data.

Evaluation on 100 JailbreakBench prompts with
GPT-4.1, serving as the evaluator, indicates that transfer is robust but exhibits distinct scaling behaviors. Llama-2 demonstrates a sharp threshold ($\tau = {0.25,0.32} \ \text{beyond} \ \alpha = -0.15$), whereas Qwen2.5 displays continuous and higher levels of transfer ($\tau$ up to $0.61$).

Submission Number: 695