first-evidence-dominance-is-representational-not-decodingmechanismsingle paper
Given several conflicting but equally legitimate passages, a model's answer is driven disproportionately by whichever passage comes first, and the skew sits in the representation of the combined prompt rather than in decoding — which is why reordering the passages does not remove it and why steering the activations does.
Capability: Checking claims against evidence · Knowledge, Retrieval-augmented QA
Observed on
2026, seven models from 8B to 120B, open and closed.
Sources
- Shapley attribution over evidence pieces gives the first passage a large majority of the contribution, a layer-wise projection shows combined activations shifted toward the first evidence at every layer, a reordering control leaves the dominance in place, and steering toward an evidence-neutral centroid raises accuracy — a causal handle on the proposed mechanism.
- The prior account of which conflicting source wins: models follow the majority and lean toward their own prior. Position is an additional determinant alongside those, not a replacement for them.
Disagreeing is the most useful thing you can do here. Both sides of every contested claim in this catalog were assembled by the same person, which is its weakest point.
Related claims
- Where a passage sits in a long input changes how much the model uses it — accuracy is highest when the needed information is at the very start or the very end and lowest when it is in the middle — so ordering retrieved passages to put the most relevant ones first is a real lever on accuracy.Losing information in long inputs · contested
- In retrieval-augmented answers, splitting an answer into claims, checking each against the retrieved source, and then acting on the flagged claims reduces the share of answers judged to contain unsupported content — but the strategies trade grounding against preservation: deleting unsupported claims reduces unsupported content most while retaining the least original text, and rewriting retains the most while reducing least.Stating false facts confidently · unreviewed
Notes
Held apart from the claim about reordering because they are different assertions. This one says where the bias lives; that one says whether a remedy works. The dataset is partly semi-synthetic and real retrieval is untested, which is why this is single-paper and why the era is recorded.