I'm frustrated by the fact that you're glossing over the key part here... but I'll only pound on a dead horse so long. Besides, not my mission to change your mind on anything. I have to reserve that energy for my stubborn kids.
“Drivers need to keep not only their hands on the wheel, they also have to keep their brains on the road,” said researcher Marcel Just. Talking on a cell phone has a special social demand, and not interacting with the caller can be interpreted as rude or insulting behaviour, he added. A passenger, by contrast, is likely to recognise increased demands on the driver’s attention and stop talking.
Just’s team used state-of-the-art functional magnetic resonance imaging (fMRI) to measure activity in 20,000 brain locations, each about the size of a peppercorn. Measurements were recoded every second. The listening-and-driving mode produced a 37 percent decrease in activity of the brain’s parietal lobe, which is associated with driving.
They steered a car along a virtual winding road either while they were undisturbed or while they were deciding whether a sentence they heard was true or false.