Here's something I've been wondering about, but I've never heard it addressed. <br /><br />I just returned from a shopping trip. At one point, as usual, I found myself behind someone talking on a cell phone while driving. When I first got my cell phone, I talked while driving, but no longer. I noticed that I was paying more attention to the phone conversation than my driving. As a phone conversation progressed, I began driving slower and slower, to the point of impeding traffic. I notice others do this as well, and it's annoying. <br /><br />What I'm wondering is, why this phonemena doesn't occur when the driver is talking to a passenger in the vehicle. Is it a direct sensory input kinda thing?