I love this clip. We were exposed to this mind trick in college. My prof there loved optical illusions, mind tricks, and other related things.

In terms of Buddhism, I was first exposed to this idea years ago. My buddhist teacher at the time asked me to go outside and find a 4 leaf clover. Up to this point I had never found one before, but I also had never really looked. So I went outside and looked over the clover patches I saw for a few minutes and couldn't find any. I went to him and reported as much. He smiled in his way and went out with me and almost instantly found not one but a few 4 leaf clovers.

"How", I asked?

"Because you don't expect to find any," He explained, "and so even if your eyes happen to come directly upon one, your mind will edit it out when it reports the image back to you and as a result you don't see what is right in front of your face"

Lesson: What we "see" is not reality, but what our minds decide is important, which is based entirely on our stereotypes and preconceptions.

This is not a controversial idea in psychology. It is well accepted there that the "reality" we see is actually a highly edited picture, first narrowed down by our eyes or ears, and then further edited by our minds to only show us what our minds consider important.

I consider shoshin to be the single most important idea in Zen. Long ago I learned to apply that, and now I too can usually find 4 (and 5 and 6) leaf clovers very quickly.