When do persona vectors first emerge during model training?

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• How do persona vectors evolve throughout the training?question0.857
  Second research question driving analysis of persona vector geometry and facet evolution
• Persona vectors do not emerge as a single capability; each persona has its own onset and ceiling ordered by prevalence and behavioral simplicity in pretraining dataclaim0.856
  Interpretive finding against a unified emergence threshold for all personas
• Persona vectors are present from the earliest available Apertus-8B checkpoint at 1.4% of pretraining (210B tokens)finding0.803
  Replication finding on Apertus confirming early persona formation generalizes across model families
• Persona representations originate in pretraining, not alignment; they form without explicit supervision as useful features for next-token predictionclaim0.793
  Core interpretive claim providing mechanistic explanation for early persona formation
• Persona vectors extracted from base pretraining checkpoints steer fully post-trained OLMo-3-7B-Instructfinding0.791
  Shows persona directions persist through all alignment stages, answering key part of RQ2
• The directional transition pattern of persona vectors at the identified attention layer represents a unique footprint of persona representations, distinct from general hidden state dynamicsclaim0.784
  Supported by comparing persona vector transitions to hidden vector transitions from OpenAssistant data
• How does different post-training data shift a model's position along persona dimensions?question0.781
  Future work direction: using persona space to study effects of training data on model character
• What is the mechanistic basis for persona vectors extracted from exhibited-trait samples generalizing to causally influence the trait?question0.774
  Key open question about why the persona vector extraction method works beyond correlation