I Wasn't Listening…

So every now and then my 17-year-old and I will have some kind of discussion that goes something like this:
Me: So why didn't you tell me about…
Him: I did tell you! You were standing right there when we were talking about it!
Me: Um, but I wasn't really listening to you.

Or
Me: Wait, you did what?
Him: But you knew we were! I told you in the kitchen, remember? You were right there!
Me: Um, just because I was standing there and looking at you, that doesn't mean I was really absorbing what you were saying.

Yes. That is a problem. He thinks I am listening to every conversation that he and his friends have; the reality is that I have the ability to completely tune them out.

And here is why. Because he used to be a nine-year-old boy who had conversations like his brother had with a friend on the way home from camp today:

N: I'm bored. Bored bored bored bored bored.
D: Me too. We're bored, we're bored.
[Both begin singing in falsetto.}
D: I farted with my eye.
N: I farted with my eyebrow.
D: I farted with my ear.
N: I farted with my bottom, which is where you really fart.
D: I farted from my belly button.
N: I'm the super fart! I'm the super hero of farts!
[This line of talk continued for 5 minutes. I timed it, and then I tuned out. When I tuned back in, I heard…]
D: My fingers are a super Ninja.
N: Hey! I invented that! I invented the finger thing!
D: Yeah, so he doing splits now and he is like [arp…chchchch…arp]
N: Yeah, and then he is like [whaHEE--arp--ch-ch-arp]
D: Yeah, and then his head was like split open on the floor…
N: Yeah, and like his legs just like fell off…
D: Yeah, and then he was like [ARP--CH CH CH]
[And so this scene continued until we were back to…]
N: Let's slap fight.
D: Yeah [slap slap slap]
N: yeah
D: Yeah!

Is it really any wonder that I am trained to tune out conversations between boys? I mean, really, "I am super fart?" and "I can fart out my eyeballs?"

Please don't judge me for not listening. You drove me to it.