AI slows down open source developers. Peter Naur can teach us why

Everyone else was an absolute Cursor beginner with barely any Cursor experience. I don't find it surprising that using tools they're unfamiliar with slows software engineers down.

I don't think this study can be used to reach any sort of conclusion on use of AI and development speed.

This. Leveraging the AI to start to develop the mental model is an advantage. But, using the AI is a non-trivial skill set that needs to be learned. Skepticism of what it's saying is important. AI can be really useful just like a 747 can be useful, but you don't want someone picked off the street at random flying it.

(The SPACE [1] framework is a pretty overview of considerations here; I agree with a lot of it, although I'll note that METR [2] has different motivations for studying developer productivity than Microsoft does.)

[1] https://dl.acm.org/doi/10.1145/3454122.3454124

[2] https://metr.org/about

1. Some prior studies that find speedup do so with developers that have similar (or less!) experience with the tools they use. In other words, the "steep learning curve" theory doesn't differentially explain our results vs. other results.

2. Prior to the study, 90+% of developers had reasonable experience prompting LLMs. Before we found slowdown, this was the only concern that most external reviewers had about experience was about prompting -- as prompting was considered the primary skill. In general, the standard wisdom was/is Cursor is very easy to pick up if you're used to VSCode, which most developers used prior to the study.

3. Imagine all these developers had a TON of AI experience. One thing this might do is make them worse programmers when not using AI (relatable, at least for me), which in turn would raise the speedup we find (but not because AI was better, but just because with AI is much worse). In other words, we're sorta in between a rock and a hard place here -- it's just plain hard to figure out what the right baseline should be!

4. We shared information on developer prior experience with expert forecasters. Even with this information, forecasters were still dramatically over-optimistic about speedup.

5. As you say, it's totally possible that there is a long-tail of skills to using these tools -- things you only pick up and realize after hundreds of hours of usage. Our study doesn't really speak to this. I'd be excited for future literature to explore this more.

In general, these results being surprising makes it easy to read the paper, find one factor that resonates, and conclude "ah, this one factor probably just explains slowdown." My guess: there is no one factor -- there's a bunch of factors that contribute to this result -- at least 5 seem likely, and at least 9 we can't rule out (see the factors table on page 11).

I'll also note that one really important takeaway -- that developer self-reports after using AI are overoptimistic to the point of being on the wrong side of speedup/slowdown -- isn't a function of which tool they use. The need for robust, on-the-ground measurements to accurately judge productivity gains is a key takeaway here for me!

(You can see a lot more detail in section C.2.7 of the paper ("Below-average use of AI tools") -- where we explore the points here in more detail.)