Predicting Personality Traits from Short Unstructured Conversations with AI

Given the complexity of personality, we might assume that significant behaviour is required to express our traits. Here we use large language models (LLMs) to test the extent to which personality is visible in short conversations with artificial intelligence (AI). In a preregistered experiment, 100 participants completed the Big-Five Inventory (BFI) before having unstructured conversations with GPT-4.1, writing a median of 430 words. We then instructed a second LLM rater (Claude Sonnet 4.6) to complete the BFI for each participant, predicting their responses based solely on an analysis of the