A red open car blasts past you, exhaust and radio blaring, going at least 10 miles faster than the speed limit. Want to take a bet on the driver? Well, you won’t get odds. Everyone knows the answer. All that exhibitionism shouts out the commonplace, if not always welcome, features of young males. Just rampant testosterone, you might say. And that’s right. It is testosterone. The young man may be driving the car but testosterone is what’s driving him.