Imagine a musician who spent ten years mastering classical piano, then decided to learn jazz. On the first day of jazz lessons, something terrible happens: the musician forgets how to play Bach. Completely. By week two, muscle memory from thousands of hours of practice has vanished. This isn’t incompetence. It’s amnesia.
This phenomenon has a name in machine learning: catastrophic forgetting. And it’s not a flaw in specific architectures or training procedures. It’s fundamental to how neural networks learn.