An Israeli study by the Hebrew University of Jerusalem found that ChatGPT can predict how groups of people will respond to personality-test questions before they take the tests. The researchers used GPT-4 to generate two personality questionnaires from very different sources: one based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), and the other based on an astrology textbook, which is not scientifically validated. Before administering the questionnaires, the researchers asked GPT-4 to predict how people would respond. They then gave the questionnaires to 600 participants, alongside the Big Five Inventory (BFI), a widely validated assessment of five broad personality traits that served as a benchmark. The participants’ responses were broadly consistent with the model’s predictions. The DSM-5-based questionnaire showed strong internal consistency, and its results also resembled those of the BFI. The study did not show that ChatGPT understands individuals or can diagnose mental illness, but it showed that an LLM could predict population-level patterns before collecting the human data needed to test those predictions. Lead author Dr. Rotem Monsa said that while LLMs were not taught psychology or personality theories, these are already embedded in the language they learn from.