You know those little picture things that come up when you want to post something on the internet, or register for something, or sign in somewhere for the fourth time having forgotten your password the first three times? The ones that ask you "in order to filter out spam and to check you're a human being, please type in the letters and numbers you see in the picture below" and then you enter in the number to prove you're a human?
I don't seem to be very good at them.
I admit that my eyesight isn't great; I nearly had the shortest driving test in the world following the question "can you please read the number plate of the silver car over there" and couldn't tell if the second letter was a V, W or an N, but it is (thankfully) good enough to read a monitor a foot away from my face. I can't however always work out what the thing is meant to say and so often fail.
Thinking about this, what you have is a computer generating a test to see if you are a human and this test can be failed by a human. Computer. Generates. Test. To tell if I'm Human or not. I don't know, that seems backwards to me.
Having now watched most of the first series of Battlestar Gallactica, I'm actually catching myself questioning my classification of human. Probably for the best not to think about that too hard.