The best evidence available does not agree with itself, and worse, it suggests that confidence is exactly the thing not to trust. That would already complicate the simple story that AI makes knowledge work faster. Before the study, the developers expected AI assistance to speed them up by 24 per cent. What the trial actually measured was the opposite: tasks done with AI took 19 per cent longer to complete. Both suggest the gap between feeling faster and being faster is not a fluke of one bad study design.