Introduction

A common meme in the LLM community is to instruct a model to “make no mistakes”, implying that telling a model to act a certain way can greatly improve the final result. In this vein, an oft-cited rule in prompt engineering is to give the model a role to play 1 . For example: “You are an expert in physics. Now answer this physics question.” This is called “persona” prompting.

While persona prompting can work for output style — e.g. prompting an LLM to act like a caveman 2 can reduce the length and complexity of its responses — it’s often assumed that personas can also improve the factual accuracy of a model’s answer.

A couple months ago, I tested the persona prompting theory in a small experiment I posted about on LinkedIn .…