Ran across this link
I then thought I would ask the guys on aus. electronics if they could figure out how it worked. You know, a fairly bright bunch who have never failed me yet when I asked about something that was actually on topic.
Fortunately, before I made a complete moron of myself, I figured it out for myself. I must have led a very sheltered internet life to be taken in for a good fifteen minutes. See below for how it works.
The first .gif is of six picture cards. The second .gif is of five picture cards, NONE of which are the same as the first six. So the one you picked is not there but neither are any of the others. Duh. Is this a case of "hiding in plain view" or "can't see the wood for the trees."?
PH