Parrots are very social creatures and if they are separated from their flock or mate, they have special, even ritualized, greetings when the human partners return. If the owner comes home from a hard day at work and ignores her parrot as she enters the house, chances are the parrot will scream for attention because one of its basic social needs is not being met. Finally, the tired owner gets frustrated and starts yelling at the bird to shut up. This type of negative learning can be avoided if the owner consistently greets the parrot as soon as he or she walks into the door. If they are strongly bonded, pet birds do react to their owner's approval or disapproval.
Parrots are aware of the expression on their owner's face.
I do not believe that parrots really understand the concept of punishment because it requires a sense of long-term cause and effect, a sense of the continuation of time and a fairly long attention span. They do, however, react in a positive way to discipline. The difference is the immediacy of discipline and the lack of drama it presents. However, discipline will not work successfully if you are not in control of your parrot's behavior. The bird must follow your guidance for discipline to be successful.