As for testosterone, it's gotten a bum rap. Yes, it has tons to do with aggression but it doesn't cause aggression as much as sensitizes you to the environmental triggers of aggression.
The visual system of the brain has the organization, computational profile, and architecture it has in order to facilitate the organism's thriving at the four Fs: feeding fleeing, fighting, and reproduction.
To be nobody but yourself in a world which is doing its best, night and day, to make you everybody else means to fight the hardest battle which any human being can fight, and never stop fighting.
If you wish to glimpse inside a human soul and get to know a man, don't bother analyzing his ways of being silent, of talking, of weeping, of seeing how much he is moved by noble ideas; you will get better results if you just watch him laugh. If he laughs well, he's a good man.
There are portions of the sovereign people who spend most of their spare time and spare money on motoring and comparing motor cars, on bridge-whist and post-mortems, on moving pictures and potboilers, talking always to the same people with minute variations on the same old themes. They cannot really be said to suffer from censorship, or secrecy, the high cost or the difficulty of communication. They suffer from anemia, from lack of appetite and curiosity for the human scene. Theirs is no problem of access to the world outside. Worlds of interest are waiting for them to explore, and they do not enter.
We begin from the recognition that all beings cherish happiness and do not want suffering. It then becomes both morally wrong and pragmatically unwise to pursue only one’s own happiness oblivious to the feelings and aspirations of all others who surround us as members of the same human family. The wiser course is to think of others when pursuing our own happiness.
Rather, for all objects and experiences, there is a quantity that has optimum value. Above that quantity, the variable becomes toxic. To fall below that value is to be deprived.
Man is a mystery: if you spend your entire life trying to puzzle it out, then do not say that you have wasted your time. I occupy myself with this mystery, because I want to be a man.
Dixit 
