^i agree with that but kinda have my doubts as well....In my opinon i dont see what the difference is when driving with the cellphone and talking to someone else in the car. You can hang up on the person on the phone but not the person in the passenger seat.

 

Having deep conversations with a passenger can be disctracting as well, but it tends to be easier to change focus, and since they also have something at stake I think it tends to change the mood a bit.
There's something about connecting with someone miles away that seems to make ones mind more diplaced. I'm not sure if you just focus more because of the volume or what.