I'm not, with the amount of people I see running red lights and stop signs every day, I just assume that people are stupid. I always assume that the people in the right lane are going to do what the OP's kid did and realize way too late that they have to get over. I always try to speed way up and get by the person I think will want to jump over in my lane or slow down to create that space in case they do. That said, I'd think the percent of people who actually think like that (anticipating) is quite low.
It reminds me of a few years ago when I was driving towards the Tappan Zee bridge outside of NYC and I saw this box truck and a BMW with a father and young kids. It was four lanes on my side of the highway and I was in the left, BMW was in 2nd to left and box truck in second to right. I was going faster than the others so coming up to pass them but there was a merge of a bunch traffic coming up on the right. I saw it coming that the box truck was going to cut off the BMW and there was nowhere for the BMW except into me so I slowed way down and it happened just the way I saw it coming and the BMW almost got sideswiped and cut right in front of me. After I passed the BMW a little later, he waved because he saw that I gave him an out. It all took just a few seconds, but it's something all drivers should anticipate and most don't.
