Link: https://www.theregister.com/2026/03/24/ai_models_persona_prompting/

Many people start their work with AI by prompting the machine to imagine it is an expert at the task they want it to perform, a technique that boffins have found may be futile.

Persona-based prompting – which involves using directives such as "You're an expert machine learning programmer" in a model prompt – dates back to 2023, when researchers began to explore how role-playing instructions influenced AI models’ output.

It's now common to find online prompting guides that include passages like, "You are an expert full-stack developer tasked with building a complete, production-ready full-stack web application from scratch."

But academics who have researched this approach report it does not always produce superior results.

In a pre-print paper titled "Expert Personas Improve LLM Alignment but Damage Accuracy: Bootstrapping Intent-Based Persona Routing with PRISM," researchers affiliated with the University of Southern California (USC) find that persona-based prompting is task-dependent – which they say explains the mixed results.

For alignment-dependent tasks, like writing, role-playing, and safety, personas do improve model performance. For pretraining-dependent tasks like math and coding, using the technique produces worse results.

Makes sense if you consider how LLMs work. No expert starts off a piece of writing with "I am an expert in math, here is a proof of Fermat's Last Theorem."

You'd get better results prompting it for a style of document. Instead of "you are a screenwriter" just start it off "Script for Harry Potter Goes for Surf n TERF. Scene 1: The Sweaty Troll, a wizard gay bar" and then let it run from there.

Usually "I'm an expert" gets followed by "here's why your question is stupid and I won't answer it". Non-powertripping experts just answer the question, or ignore it if it really is dumb.

Reminds me of how I got taught to google shit like 20 years ago before social media and SEO: don't ask "how can I do x", write "doing x", as that would find you a website explaining doing the thing and not some BBS post of a person asking about it.