A good analogy that I like to use to explain the difference between a terminal marker vs a duration marker is- if I were a dog and you wanted to isolate the behavior of teaching me to grab the door handle, which marker would you use ? The terminal marker OK or The duration marker YES? Let’s demonstrate this to find the answer. you say grab I will grab the handle , because we want to teach me to grab the handle the terminal marker OK has to be given right when I have grabbed the handle. If you were to say YES it would teach me to hold the handle. As the Yes marker means continue performing the behavior. As you see when you say YES to your dog when they perform a command you are essentially telling them to keep performing a sit. This means that they have to wait for the Terminal marker OK before they can move to receive the reward and be released from behavior. It is important that we keep the integrity of communication consistent. This means when we say yes and feed in place we cannot forget about our dog and let them break out of the behavior. Always release them with the Terminal marker .