Is Testosterone a Cause of Aggression?

In lots of ways, the testosterone story, it doesn't cause aggression and it amplifies the pre-season, it's getting tense. Little inter-individual differences, the fact that I've got a little more testosterone today than that guy does or than I had yesterday predicts virtually nothing about behavior. The ways that we identify at this kind of very deep level are not arbitrary, are they? They're not just, oh, these are my friends. This is how I grew up.