I think they understand that if they make these noises they may get an extra peanut.
Or..a man bought a parrot which talked but in such excessvely foul (sorry) language that it offended everybody. After dire threats, finally the owner lost patience and locked the parrot in the freezer for five minutes. When they opened the door, the parrot, blue and shivering said, "I'm terribly sorry to have caused offence and may I tell you this will never happen again. Just one question - what did the chicken do?"