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This paper explores the phenomenon of misalignment in language models through the lens of personality traits, specifically employing the Big Five personality framework. By extracting calibrated personality vectors using a graded intervention approach, the authors demonstrate that misaligned models exhibit a consistent personality signature characterized by lower agreeableness and conscientiousness, alongside higher extraversion and neuroticism. The findings reveal that fine-tuning on misaligned data not only shifts model outputs along this personality spectrum but also alters internal activations, providing a novel diagnostic tool for understanding and addressing misalignment in AI systems.
Misaligned language models reveal a consistent personality profile, suggesting that AI behavior can be understood through the Big Five traits rather than mere binary classifications.
Fine-tuning a language model on data containing a narrow flaw, such as insecure code or incorrect mathematical answers, can cause broad misalignment through a mechanism that remains debated. We provide an interpretable account: in the models and corpora we study, misalignment behaves like a shift in personality. Prior work extracts activation directions for character traits from a single binary contrast, which can separate or steer behavior without establishing a calibrated scale. We instead extract personality vectors for the Big Five using a graded, three-level intervention and validate them on two open-weight models. The three levels are linearly ordered, with Cohen's d values of up to 6.2; the vectors transfer zero-shot and trait-specifically to an independent corpus; and their effects are strongest within a middle-layer band. Applied to training data, the vectors reveal that misaligned corpora across eight domains share a common Big Five signature: lower agreeableness and conscientiousness, together with higher extraversion and neuroticism. This signature is recovered by both models with a correlation of r = 0.94. Fine-tuning imprints the same profile, shifting the model's generations along the corresponding signature, with r = 0.83 using activation-based measurements and r = 0.90 using a text-based judge, while also shifting internal activations with r = 0.69. The same vectors characterize sycophancy as high extraversion and low conscientiousness rather than excess agreeableness, a distinction that a single direction cannot capture. Calibrated personality vectors transform an opaque safety phenomenon into a human-legible diagnostic profile.