stupid scientist

There was this not too bright scientist doing a study on how frogs respond to commands.
He tells a forg to jump. The frog jumps 30 feet. He logs it down.
Then he cuts off one of his legs and commands the frog to jump again. 25 feet this time. He logs it down.
He cuts off the third leg and the frog jumps only 10 feet.
finally, he cuts the last leg off and commands the frog to jump.
The frog doesn't move.
The stupid scientist writes in his log book, ' Cut off all 4 legs and frog goes DEAF'