Please understand that we are apologists, not parenting experts. I can only give you an opinion. If you need more than that, I can only recommend consulting with a child counselor.
Having said that, my own feeling is that a 16-month-old may not understand what “I’m disappointed in you” means, but you are building a habit of saying that to him for what sounds like minor offenses, in this case done by a child not even two years old. A child that age needs constructive redirection and physical separation from the ability to do whatever it is he has done that annoys you. He does not need a litany of parental disappointment. The danger though might be that, if this is your habitual response now to babyish naughtiness, how will you respond when he is older and capable of being hurt by hearing on a weekly basis that he is a disappointment to his parents?
I’m not saying that an occasional “I’m disappointed in you” may not be appropriate, but only that it should be saved for the gravest of offenses that have been deliberately chosen by an older child capable of reason (e.g., cheating on a test, bullying a classmate, purposeful destruction of property, ingesting illegal substances, etc.). For minor offenses, a better solution might be to capture the child’s complete attention and say firmly, “I expect you to obey me when I tell you to stop pulling the cat’s tail.”
