To Copy or Not to Copy: Copying Is Easier to Induce Than Recall
- URL: http://arxiv.org/abs/2601.12075v1
- Date: Sat, 17 Jan 2026 14:46:29 GMT
- Title: To Copy or Not to Copy: Copying Is Easier to Induce Than Recall
- Authors: Mehrdad Farahani, Franziska Penzkofer, Richard Johansson,
- Abstract summary: Language models must arbitrate between parametric knowledge stored in their weights and contextual information in the prompt.<n>This work presents a mechanistic study of that choice by extracting an empharbitration vector from model activations on a curated dataset.
- Score: 5.057026826740146
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: Language models used in retrieval-augmented settings must arbitrate between parametric knowledge stored in their weights and contextual information in the prompt. This work presents a mechanistic study of that choice by extracting an \emph{arbitration vector} from model activations on a curated dataset designed to disentangle (i) irrelevant contexts that elicit parametric recall and (ii) relevant but false contexts that elicit copying. The vector is computed as the residual-stream centroid difference between these regimes across 27 relations, and is injected as an additive intervention at selected layers and token spans to steer behavior in two directions: Copy$\rightarrow$Recall (suppressing context use) and Recall$\rightarrow$Copy (inducing the model to copy any token from the context). Experiments on two architectures (decoder-only and encoder/decoder) and two open-domain QA benchmarks show consistent behavior shifts under moderate scaling while monitoring accuracy and fluency. Mechanistic analyses of attention routing, MLP contributions, and layer-wise probability trajectories reveal an asymmetry: inducing copying is an easy ``reactivation'' process that can be triggered at different locations in the input, while restoring recall is a ``suppression'' process that is more fragile and strongly tied to object-token interventions.
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