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Summing Up the Facts: Additive Mechanisms Behind Factual Recall in LLMs

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arxiv 2402.07321 v1 pith:ZZNHW2HD submitted 2024-02-11 cs.LG cs.CL

classification cs.LGcs.CL
keywords additivefactualrecallsummingattributebehindcorrectdifferent
verification ladder T0 review T1 audit T2 compute T3 formal
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How do transformer-based large language models (LLMs) store and retrieve knowledge? We focus on the most basic form of this task -- factual recall, where the model is tasked with explicitly surfacing stored facts in prompts of form `Fact: The Colosseum is in the country of'. We find that the mechanistic story behind factual recall is more complex than previously thought. It comprises several distinct, independent, and qualitatively different mechanisms that additively combine, constructively interfering on the correct attribute. We term this generic phenomena the additive motif: models compute through summing up multiple independent contributions. Each mechanism's contribution may be insufficient alone, but summing results in constructive interfere on the correct answer. In addition, we extend the method of direct logit attribution to attribute an attention head's output to individual source tokens. We use this technique to unpack what we call `mixed heads' -- which are themselves a pair of two separate additive updates from different source tokens.

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Forward citations

Cited by 4 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Verbalizable Representations Form a Global Workspace in Language Models

    cs.CL 2026-07 conditional novelty 7.0 of 10

    Language models represent their current reasoning in a small, readable set of verbalizable vectors (the J-space) that functions like a global workspace.

  2. All for One: LLMs Solve Mental Math at the Last Token With Information Transferred From Other Tokens

    cs.CL 2025-09 conditional novelty 6.0 of 10

    LLMs solve arithmetic in-context via an All-for-One pattern, with all input-specific computation occurring at the last token after a two-layer information transfer window.

  3. Failure by Interference: Language Models Make Balanced Parentheses Errors When Faulty Mechanisms Overshadow Sound Ones

    cs.CL 2025-06 conditional novelty 6.0 of 10

    Language models fail at balanced parentheses because unreliable internal components that promote wrong tokens can outvote reliable ones, and amplifying reliable components fixes the errors.

  4. Paths Not Taken: Understanding and Mending the Multilingual Factual Recall Pipeline

    cs.CL 2025-05 conditional novelty 6.0 of 10

    LLMs recall facts through an English-centric internal path and then translate the answer; injecting a translation vector and a recall vector raises accuracy by over 35 percentage points in the weakest language.

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