How did he know?

Last night while Jason and I were making dinner we would every once in a while starting kissing, hugging, etc... While we were kissing, Brady walks into the kitchen and says "DON'T!" We stop and he comes up to Jason and starts spanking him and says "NO" and then did the same thing to me! Silly Kid! We stopped, continued with dinner and then start kissing again. Brady walked in again and said "Don't." How did he know? We couldn't help but laugh every time!