lucy24 - 9:00 pm on Jul 5, 2013 (gmt 0)
Would I have to cease speaking to my friend in order for the checkout operator to do their job? No.
Yes. You would-- and you do. How else do you find out how much money you are expected to hand over, if 100% of your attention is on your friend?
Talking to a human passenger while driving is different because the reduced attention to the road is counterbalanced by the second set of eyes and ears:
Oi! Watch out for that motorcycle!
That's our turnoff coming up.
Oh, there's a CheapGas station. Weren't you looking for one?