When you return to school after summer break, it may feel like you forgot everything you learned the year before. But if you learned like an AI system does, you actually would have -- as you sat down for your first day of class, your brain would take that as a cue to wipe the slate clean and start from scratch. AI systems' tendency to forget the things it previously learned upon taking on new information is called catastrophic forgetting. See, cutting-edge algorithms learn, so to speak, after analyzing countless examples of what they're expected to do. A facial recognition AI system, for instance, will analyze thousands of photos of people's faces, likely photos that have been manually annotated, so that it will be able to detect a face when it pops up in a video feed.