My mom talks about when she moved in with her sisters in CA, she discovered that they were way the hell too chipper first thing in the morning (this is funny because my mom is a bona fide morning person.) It nearly came to blows before they figured out not to talk to her for at least an hour after she got up. Difference from the family home was that it was a farm and everyone had specific chores that pretty much kept them busy first thing.
Of course, she did not apply this lesson to me. It took until ( well....she still slips up) these days for her accept that I cannot and will not converse, or for that matter even comprehend, first thing in the morning.