Oral Presentation: Not Neurotic Enough!: Behavioural Asymmetry Across Activation Interventions for Big Five Personality Control in LLMs, by Ms. Hala Sheta (University of Waterloo)

Recent work in Mechanistic Interpretability and Alignment has explored the steerability and localization of persona traits, usually focusing on alignment-relevant traits such as `evil' or observing task generalization in other domains, rather than varied personality expression. In this work, we systematically compare different interventions for steering Big Five personality traits in small instruction-tuned Llama models, across both high- and low-trait directions. Our results demonstrate that activation addition is the only method that reliably amplifies and suppresses trait expression across all five traits, in both high- and low-trait directions. Probe steering and directional ablation achieve partial control at best, failing to produce consistent bidirectional effects. Steerability also varies substantially across traits: Agreeableness and Extraversion respond most reliably to intervention, while Neuroticism resists steering in both directions. These results show that not all activation-based interventions are interchangeable, despite sharing the same geometric direction.