if you can’t actually see the frog or yo see only a horse it may be due to two things; namely
1. The inability to unravel the puzzle of the illusion or the inability to solve the problem of the illusion.
illusions are confusing though, bought can be unravel by persons quickly or slowly
2. Before reading an illusion, one must have a rest of mind or a good state of mind because your state of mind tends to tell you what you see.
Looking at the picture above may puzzle you but looking at it from a different direction may give an answer.
Thanks