Study Finds AI Tools May Slow Down Experienced Developers’ Task Completion Time

A new study by AI research nonprofit METR found that using AI tools like Cursor actually slowed down experienced developers by 19%, contrary to expectations of a 24% speedup. The developers, working on familiar open-source projects, had to spend extra time reviewing and correcting AI suggestions. While earlier studies reported productivity gains with AI, this research suggests such benefits don’t apply in all contexts, especially when developers already know the codebase well. Despite the slowdown, participants still preferred using AI for the ease and comfort it offers, comparing it to editing rather than starting from scratch.