A few years ago a young man, age 16, was killed when the truck he was driving was struck head-on by the truck a friend of his was driving. He had been playing "chicken" with a friend. That is, he was challenging his friend to see who would stand his ground the longest while driving towards each other at significant speed. A news reporter called a developmental psychologist to ask whether a young person of age 16 would understand that if he was hit head-on by another truck, he might be killed. The developmental psychologist answered, "Yes. He would know this, but that would not explain his behavior.