The paper zeros out specific attention connections corresponding to each step of the proposed circuit in Llama 3 8B and Falcon 7B, then measures ICL accuracy on 6 classification datasets. Removing demonstration-text-to-forerunner connections (step 1) drops accuracy by up to 30.60 percentage points; removing query-text-to-forerunner by up to 28.38; removing forerunner-to-label (step 2) by up to 3.45; and removing label-to-query-forerunner (step 3) by up to 11.36. Controlled experiments with randomly ablated connections of equivalent size show negligible drops (within ±0.02). The results confirm the circuit is causally dominant, though bypass mechanisms (direct decoding, shortcut induction) partially compensate.
Ablation is applied from bottom to top layers; the result without induction (step 3) is better than zero-shot, indicating bypass mechanisms. The paper acknowledges the circuit is not the only mechanism and that bypasses exist in parallel.