NPR's Science Friday program this week featured an intestesting segment on How We Pay Attention. As part of the show, they included these two video tests available on their site.
Watch the first video, then watch the second. I wound up wrestling with frame drops from YouTube, so you may want to try and let the entire video load before you watch it.
1. Here's the first video:
2. Here's the second video:
Here's a link to the Science Friday segment on attention on NPR.
Here's a link to the book that's referenced in the segment. I won't mention the title as it might work like a spoiler for your video tests. FYI, there's more great stuff on their web site.