What about C.B. Radios? What is the difference in talking on one of them and a cellphone?
someone else can probalby put it in words better than me, but for the most part cb chatter is not a CONVERSATION directed at you every time you finish talking. it is more like listening to a telegraph. you talk *when convenient, with possibly long delays between comments*, then put the mic down and see what noises come out of the box, if any. The parts of the brain and attention it uses do seem substantially different.