my gifted DH has the opposite problem...I talk to him, or ask him a question, and after several minutes of me blathering on (or silence on his end) I realize he was somewhere in space (literally, he's an astrophysicist, lol) I often find myself having to repeat things or stopping to 'check' if he's tuned in.
Flip side: My DW frequently enters the room to shower me with an avalanche of information before having established my attention first, where I'm probably already focused on something. As a consequence, she gets to repeat it all again. And then she acts like I'm the problem for being a poor listener. What's wrong with a simple, "Hey."?
Actually, there really is some (not definitive) research that suggests that males are better able to tune out additional conversations and focus narrowly on one conversation, while females can attend to multiple conversations at once, but typically capture slightly less detail than a man focusing on his one conversation.
In my experience, tuning out is a learned skill, and it's taught through play. Think of all the chatter Little Leaguers throw at the batter. Boys do this sort of thing to each other in various sports ALL. THE. TIME.
Can't make a play on the ball because you're out of position? Shout. The other guy will probably fail spectacularly, and everyone gets a good laugh.
After you're that guy a few times, you start working on shutting out distractions.
