Check out
this scene, and see how long it takes you to figure out what changes when the scene flashes. I'll give you a moment.
OK, back? It might have taken you a few moments, but you probably noticed eventually that the plane's engine, on the wing near the fuselage, disappears and then comes back in successive flashes. The difficulty people have in noticing changes like this is called change blindness. There's a pretty large literature on change blindness, and I don't want to get into all of that right now, because I want to get to the coolest... experiment... ever, but I will give you a few of the conclusions from the literature, from Simons and Ambinder (p. 44)1:
1. "Change blindness occurs whenever attention is diverted from the change signal."
2. "Changes to objects that are central to the meaning of the scene or changes to visually distinctive objects are detected more readily than other changes, presumably because observers focus attention on important objects
3. "Attention may be necessary for change detection, with changes to unattended objects going unnoticed."
4. "Attention to a changing object may not be sufficient for change detection; observers frequently fail to detect changes to the central actors in motion pictures and to real-world conversation partners even though these people clearly are attended suggesting that change detection requires observers to encode the changing features before and after the change and compare them"
