I've been able to do this since before my son was talking. Hubby has a problem doing this. He can't get past the high pitched voice screaming, "Mommy, mommy, mommy!" over and over from the back seat or the living room. I have no problem whatsoever, probably b/c I have spent the last 8 hours w/ no one but these small people to talk to and once an adult comes w/in 10 feet of me, I can't contain my mouth.
I first realized this gift one Friday when my family was driving 6 hours to visit the grandparents. I had worked that day (I worked part time before we moved), Hubby had worked, we were both tired but as was our routine he drove the first leg of the trip. I was sitting in the passenger seat chattering away about who knows what while my son tried to be heard from the back seat. He kept repeating, "Mommy, mommy, mommy." His volume never changed, just the intensity and speed of the phrase. I kept jabbering away to Hubby like we were the only 2 in the car. Finally Hubby says, "Can you not hear that?" I looked at him blankly for a minute before turning around and answering the inane question my son just had to have an answer to in that very second.
Further proof that men cannot multitask.