The 'Expert' AI Prompt That Kills Accuracy

USC Study Finds Persona-Based Prompts Lower Factual Accuracy Rashmi Ramesh (rashmiramesh_) • March 25, 2026

A coder tells its chatbot: You're an expert. A full stack developer. It's machine massaging technique that's a cornerstone of persona-based artificial intelligence prompting - and it backfires spectacularly, find academics in a studying showing the practice produces worst results, when the goal is accuracy.

See Also: AI Is Transforming the Chief Data Officer Role

Researchers at the University of Southern California in a preprint

The study found that the effect of stoking a large language model with the "you're an expert" prompt consistently damaged performance. Their advice is to avoid persona-based prompts for tasks that require models to tap into their pre-trained knowledge - the heaps of coding examples fed into models before they're ready to interact with customers.

The "you're an expert" prompt appears to push models into ...