My 4-month-old puppy is very smart and already knows the command to sit and lie down. The only catch is that she will only do that on the carpet, or any other soft material, but not the wood flooring or linoleum. To make it stranger, or funnier, whenever I command her to sit while she's standing on the floor, she would step backwards until she reaches the carpet and sit. It's cute, but I want her to sit on the floor as well. Any suggestions?