Every time you ask ChatGPT to help draft an email, vent about a relationship problem, or look up symptoms, you might be handing over more than just a query. As reported by TechXplore, Researchers at ETH Zurich trained an AI model to predict personality traits directly from real ChatGPT conversation logs, and it was scarily good at recognizing personality traits.
The study collected 62,090 real conversations from 668 ChatGPT users. Participants also completed a standard personality test, giving the researchers a baseline to measure against. The AI was then trained to classify each user as low, medium, or high across the five traits: openness, conscientiousness, extraversion, agreeableness, and neuroticism.
The fine-tuned model beat random chance across all five traits, with extraversion being the easiest to predict, achieving up to 44% higher accuracy than guessing.
Does it matter what you talk about?
The study found that chats involving mental health topics made extraversion particularly easy to infer. Discussions about religion were strongly linked to conscientiousness inference, and conversations about mental state and mood made openness more predictable.
Even seemingly casual conversations contained enough signal to be useful. The researchers also found that the more you use ChatGPT, the easier you become to profile. Given how much data we share with ChatGPT, it matters a lot whether it can easily discern our personality traits.
Recently, ChatGPT has started integrating ads. With the data it has on hands for us, think how easily it can format the ads to manipulate our thinking.
Why does this matter beyond the research lab?
The researchers are clear about the implications. Service providers already have access to all of this data, and with over 800 million monthly ChatGPT users as of January 2026, the scale of potential profiling is enormous.
A personality profile built from your chat history could be used for targeted advertising, personalized persuasion, or in worst-case scenarios, large-scale influence campaigns.
For now, it is worth remembering that your AI chatbot is not a diary. At least not a private one. You can also take a proactive approach and delete your ChatGPT history regularly to remove your personal chats from its memory.