Animals don't speak our language, no matter how much we think they do. Outside, NO, treat, squirrel, leave it...those are our words, not theirs. They only mean something to the dog once we teach them that it means something.
If you didn't know English and did something you weren't allowed to do and someone walked up to you and pointed in your face and screamed "NO," would you have any idea what they meant? Did NO mean look at them? Did NO mean YES?
When we teach our dogs (or any of our animals), remember we our teaching them a language. It should always be crystal clear to them what a word or a hand signal or an object means, or we won't be speaking the same language.
During training, think of teaching a new skill just as you would sound out a new word you are learning.
You wouldn't sound out the third syllable before the first and second, right? It should be the same for your dog. Break down the steps so that they can learn properly and mark those steps toward the end behavior.
If you are in the park and ask your dog to sit and he just stares at you, try not to assume that he is just being stubborn. Look at the situation and yourself before you blame the dog and the answer to the problem might be right in front of you.
If they aren't doing what you want them to do, make sure you're both speaking the same language.
If they aren't doing what you want them to do, make sure you're both speaking the same language.