Gunny and Childress79: I think you guys are looking at this the wrong way. Aggressive behaviour can be a conditioned response. Whether that means a tackle or a gunshot, it still fits in the same general category. Obviously things can't be analyzed at the level of specific behaviors (i.e. birds pressing a button when cued with a colored light), but the overarching premise here is still relevant. You guys are trying to argue out of this on a technicality. Though no scientist has established a clear causal link (and guys debating this on a message board sure won't be able to), I would say that it's pretty likely there is a connection between being trained to act aggressively on a football field and being unable to control your agression off of it.