In early 2026, Anthropic researchers ran an experiment with 52 junior developers. Half used an AI assistant to learn an unfamiliar Python library. The other half worked without one. Both groups finished the task. But when tested on how well they understood the code they had just written, the AI-assisted group scored 50% on a comprehension quiz - versus 67% for the unassisted group. That 17-percentage-point gap has a name: cognitive debt. It is one of the most important concepts in software engin