We all seek out stress. We hate the wrong kinds of stress but when it's the right kind, we love it - we pay good money to be stressed by a scary movie, a roller coaster ride, a challenging puzzle.

What does the frontal cortex do? Gratification postponement, executive function, long-term planning, and impulse control. Basically, it makes you do the harder thing.

Pulling a gun's trigger can be an appalling act. But if it is suicidal drawing fire to save someone, it has an utterly different meaning. Placing your hand on someone's arm can be an act of deep compassion or the first step of betrayal. The punch line? It's all about context, and the biology of context is vastly more complicated than the biology of the behavior itself.

If a rat is a good model for your emotional life, you're in big trouble.

The regulation of genes is often more interesting than the genes themselves, and it's the environment that regulates genes.

Finish this lecture, go outside, and unexpectedly get gored by an elephant, and you are going to secrete glucocorticoids. There's no way out of it. You cannot psychologically reframe your experience and decide you did not like the shirt, here's an excuse to throw it out - that sort of thing.

Individual differences in testosterone level predict very little about differences in aggression.