Selective Hearing. If we heard it, how do we select not to hear it?

   I think that everyone can relate to this problem. Of course, couples would be the first to jump in and complain. However, children and coworkers are also afflicted with this disease.
    Selective means having the power to select. The example the dictionary gives is perfect.  "Radio, tending to select a specific station".
   According to one of my Psychology textbooks, Attention is selective. And also shiftable. We do receive many perceptions at once, and we do truly have to filter things out or we would be unable to  do anything because we would be bombarded by all our senses at once. It's good thing our brains know how to work this shit so we can focus on what we want. Or sometimes, when we don't have a choice, what's in front of us.
   So, why, when we are communicating with our spouses, do they not hear all the words? How do they manage to select out the ones that would make what you said, not insulting or commanding or mean? Yesterday my husband asked me to get him information from my gym. I said, I would, but they wouldn't have any because they make you come in so they can force you to sign up. If you read something you'd go, ah, maybe tomorrow. What did he hear? Not the "I would", but all that followed it. I heard in his voice, a response of , yeah, go f---- yourself. Not wanting to leave on that note I asked what was wrong which was good. He didn't hear that I would, so he was pissed at me for not doing something he asked.  By the way, I asked and was sent to the sales director who didn't have anything because they are always having specials. Had I not already had a huge problem with signing up, not gonna go into that now, I might have asked if they were taking out the pool, or replacing the machines or adding a gift shop or any other structural changes that would make a brochure out of date. But I didn't.  He doesn't' know how lucky (happy) he was.
   Our communications skills suck.  Maybe they always did and always will, but what part of our brain selects out the good part and leaves in the bad? It rarely works the other way around. Like your wife says you need a haircut because you look like Einstein and he hears you complementing him as being as smart as Einstein?
   As often as you will see, I will go back to our Paleolithic DNA. Everything was dangerous when our human lives began. We had to feel, sense, hear and see anything that might be a threat to or survival. So, fast forward and our ears are on the look out for something threatening. Will be ever catch up? I don't think so. If it did, I've have nothing to think or write about.