A pouting dog is responding to your demands under protest. It can be a form of dominance behavior in a dog with a dominant personality. It knows it will probably have to do what you asked, but it's sending a clear message that it isn't pleased with the situation.

How do I stop my dog from pouting?

Ideally, get your dog to quietly sit or lie down; then reward it with attention and praise or a treat. Don't give in immediately to your dog's "want" as this actually trains it to whine about everything. This is the most common cause of problem whining.

Do dogs know if you are mad at them?

Your dog will know when you are mad.

Dogs hate to disappoint and can sense the emotions and body language that comes with an upset "parent". When you are upset with your dog and he gives you those "sweet puppy dog eyes" he knows that you are upset and is hoping to change things.