Hand gesture CAPTCHA

There are programs (by Google as I remember), which can recognize them almost as easily as you, did you know that? Nowadays AI becomes more and more powerful - we should take it into account.

 

No I don't believe there is a program that can distinguish a cat from a dog in a picture. I believe that was just your assumption. In any case it's irrelevant... matching finger tip to finger tip is just a ridiculous waste of a visitors time and it would just piss the person off trying to register. I'm baffled as to why you ever thought this was a good idea....

 

Actually, it's real - GoogLeNet. I don't know how smart it is exactly, but have no doubts in its potential. Hand gesture is an absolutely different task. Actually, you can treat it as a deformed surface, where you should recognize its 3d geometry in just one right way. As I know, there are a lot of problems for current automatic systems in doing this. Kinect, Leapmotion, etc. with all their cameras only prove this fact. So, at least for the present moment, I believe, it's a quite reliable way to baffle AI.
Your hand is a very special object, by the way. For instance, try to imagine on such picture the limb of some ... alien. Suppose it has a completely different anatomy. I can bet you would distinguish absolutely nothing in this mess. You would never tell concave parts from convex ones. So, even the visible relief would stay a mistery for you. Moreover, even if you spposedly know its anatomy quite well, it would give you not much - it would be possible to recognize only simple gestures there. It may seem strange but it's true.