There's a scientist and a frog in a lab. The scientist is performing an experiment on the frog. The scientist puts the frog on the lab table and says, "Jump frog, jump!"
The frog jumps.
The scientist writes on his paper, "frog with four legs jumps."

The scientist then cuts off one of the frog's legs, and again says, "Jump frog, jump!"
The frog jumps.
The scientist writes on his paper, "frog with three legs jumps."

The scientist then cuts off another leg and says, "Jump frog, jump!"
The frog again jumps.
The scientist writes "frog with two leg jumps" on his paper.

He then cuts off a third leg and says, "Jump frog, jump!"
The frog jumps and the scientist writes on his paper, "frog with one leg jumps."

Then he cuts off the final leg and says, "Jump frog, jump!"
The frog doesn't move.
The scientist again says, "Jump frog, jump!"
Again, the frog doesn't move.
So the scientist picks up his pencil and paper and writes, "frog with no legs is deaf."