Developers Think AI Makes Them 24% Faster. It Actually Makes Them 19% Slower.

Developers using AI coding tools believe they're 24% faster. Measured objectively, they're actually 19% slower . That's a 43-point perception gap, and it explains a lot about why AI tool adoption keeps rising while trust keeps falling. The data comes from the METR study, which measured experienced open-source developers working on their own repositories with tasks they selected themselves. This wasn't a lab experiment with toy problems. These were real developers doing real work, and the AI made them measurably less productive while making them feel more productive. Here's what's actually happening, and why it matters for how you use these tools. The perception gap is the finding The headline "AI makes you slower" is catchy but misses the point. The real finding is that developers can't tell whether AI is helping them or not. The study found that developers consistently overestimated the time savings from AI assistance. They reported feeling faster, more confident, and more productive.