Exploring Change Blindness

There's a trick for those side-by-side stills without a flicker. If able, go cross-eyed focusing between them to converge upon a 'third' image. If you've done stereograms, you'll know. Differences will show up easily as hazy and not so static if you gaze around a bit.

This is also related to how horrible eye witness testimony can be. There are good demonstrations of change blindness on Youtube. The human brain is incredibly awful at visual recall like this, regardless of advanced warning to concentrate. The longer a delay, such as by inserting a black frame in between, or diversion, the harder it is to spot differences between scenes. Here's a classic:

"Test Your Awareness : Whodunnit?"

http://www.youtube.com/watch?v=ubNF9QNEQLA

This used to be a big problem in astronomy, before the introduction of computers. Astronomers would use a special device, called a "blink comparator", to rapidly switch between two pictures so they could see the changes between them. (This is how Pluto was discovered.)