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Can we predict keyword priming before learning happens?

Exploring whether the degree to which newly learned keywords contaminate unrelated contexts can be predicted from measurable properties before training begins, and what mechanisms enable this prediction.

Synthesis note · 2026-02-23 · sourced from MechInterp

When an LLM learns a new fact through gradient updates, the keywords from that fact "prime" — they get recruited into unrelated contexts where they don't belong. Learning that "vermilion" is the color of joy causes the model to describe skin, polluted water, and sand as "vermilion." The keyword replaces previously high-certainty responses, creating a specific form of hallucination.

The central finding: priming is predictable before learning. Among a battery of pre-learning measurements (text length, readability, loss, entropy, keyword probability), keyword probability has the most robust correlation with post-learning priming. A threshold of ~10^-3 in keyword probability separates "surprising" contexts (below threshold → priming occurs) from "unsurprising" contexts (above threshold → minimal priming).

This holds across:

The dynamics of contamination are concerning:

Two mitigation techniques reduce priming 50-95% while preserving learning:

  1. Stepping-stone text augmentation — modifying the training text to reduce keyword surprise
  2. Ignore-k update pruning — pruning the most affected parameter updates

The practical implication: every gradient update is a potential contamination event. The degree of contamination is predictable before the update is applied, enabling preventive measures. This connects to How much poisoned training data survives safety alignment? — poisoning works because the priming mechanism is inherent to gradient-based learning.

Inquiring lines that read this note 57

This note is a source for these research framings, grouped by the broader line of inquiry each explores. Scan the bold lines of inquiry; follow any specific question forward.

Why do training associations persist despite contradictory contextual information? What are the fundamental limits of prompting for language models? How do curriculum design and feedback approaches affect model learning? How can persistent memory architectures preserve information across ultra-long contexts? What limits language model accuracy in evaluating ideas? How do interpretive frames override surface features in text comprehension? How does fine-tuning trade off accuracy against reasoning quality? How do transformer attention patterns implement retrieval and reasoning? Do accumulated memories help or hurt continual learning in models? Is embodied interaction necessary for language meaning and agency? Can AI systems evade safety evaluations through reasoning manipulation? Does preference optimization undermine conversational grounding in language models? How do neural networks learn compositional structure from training? What determines AI's persuasive power and how can it be detected or mitigated? Why do models reveal hidden associations despite concealment attempts? Can models develop genuine introspective capability, or only mimic it? Does pretraining establish the ceiling for what reward learning can improve? When should retrieval systems decide to fetch new information? Why do vector embeddings fail at capturing task-relevant relationships? Should models ask for clarification when facing ambiguous or under-specified information? What structural biases does transformer attention architecture inherently introduce? How does scaling reasoning capabilities affect models' appropriate abstention behavior? Can persona profiles improve LLM prediction accuracy and consistency?

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Original note title

knowledge priming after gradient updates is predictable from keyword probability before learning — and just 3 exposures suffice