are you guys talking about the depth perception test? We have that for our physicals in the AF. Sometimes you have to sit there for a minute and let your eyes "discover" which one it is. At first you can't tell, but slowly it seems to become more apparent.
An additional "hint" for all those taking the depth perception (floating circle) test. It is NEVER the 1st or 5th circle. The correct choice will always be either the 2nd, 3rd, or 4th circle.
In my case:
GJ - "Circle 3"
Med Tech - "ahhh"
GJ - "Circle 2"
Med Tech - "hmmm"
GJ - "Circle 4, there it is, I see it now, it's Circle 4."
GJ