As long as experiencing your optimal level of good stress doesn't damage others, it's hard to objectively define where normal enjoyment of stimulation becomes adrenaline junkiehood.

Perhaps most excitingly, we are uncovering the brain basis of our behaviors - normal, abnormal and in-between. We are mapping a neurobiology of what makes us us.

Some Poor grad student pressing on the flanks of a hamster and out comes a doctorate on the other side

Importantly, rather than promoting aggression, testosterone promotes whatever is needed to maintain status when challenged.

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.

Genes are important for understanding our behavior. Incredibly important - after all, they code for every protein pertinent to brain function, endocrinology, etc.

...when doing science (or perhaps when doing anything at all in a society as judgmental as our own), be very careful and very certain before pronouncing something to be a norm - because at that instant, you have made it supremely difficult to ever again look objectively at an exception to that supposed norm.