We gave 45 psychological questionnaires to 50 LLMs. What we found was not “personality.”

What is the “personality” of an LLM? What actually differentiates models psychometrically? Since LLMs entered public use, researchers have been giving them psychometric questionnaires, with mixed results. Their answers often do not seem to reflect the same psychological constructs these tests measure in humans. So we asked a slightly different question: What do LLM responses to psychometric questionnaires actually reflect? We analyzed responses to 45 validated psychometric questionnaires completed by 50 different LLMs. The strongest source of variation was whether a model endorsed items about inner experience: emotions, sensations, thoughts, imagery, empathy, and other forms of first-person experience. We call this factor the Pinocchio Dimension. Importantly, the Pinocchio Dimension is not a classical personality trait. It does not tell us whether a model is “extraverted,” “neurotic,” or “agreeable” in the human sense. Rather, it captures the extent to which a model treats the language of inner experience as self-applicable: whether it responds as if it had feelings, mental imagery, and an inner point of view, or instead as a system that reacts behaviorally to inputs. Preprint in the comments.