I'm wondering if you've experienced this.

Driving down a street and someone starts to walk across, actually jaywalk, but that doesn't matter right now. They start to either walk really fast or slightly jog until they see the oncoming driver slow down then they walk REALLY slow the rest of the way across the street forcing the driver to slow down even more.

What's up with that? Why didn't they continue to cross the street with the same sense of urgrency?