With  ice water in their veins, and ever so charming smiles, psychopaths comprise anywhere from 0.6% to 4% of the total population. This personality disorder affects males more often than females.  It’s well documented in societies around the globe.

The psychopaths brain is wired a little different to yours or mine. It has a smaller prefrontal cortex—the section that regulates behavior, impulse control, and planning—and a deformed amygdala, the home of negative emotions such as fear, guilt, and sadness.
You cannot tell externally who is a psychopath.  So here are some tell tale signs.

Psychopathic Trait #1: Fearless Dominance

Try to imagine complete freedom from fear, anxiety, or guilt.  You can act however you wish without the annoying controls of conscience, legal consequences, authority figures, or worrying about the happiness of others.  You understand the rules of society; you just could not care less about them.

You’re also a master at hiding your cold-hearted self-confidence.  Externally you’re charming, outgoing, charismatic, and convincing—people like you.   You’re not a loner. You love control and power, which you get from these sheep that take this thing called responsibility seriously.  But they’re far beneath you.  These suckers should lose—they had it coming.  You look out for yourself – and that’s it.

You also have absolutely no empathy and you’re free from emotionally dealing with the pain you inflict on people. You understand emotion intellectually, and you study it to learn how to act normally and what to say to get your way; you are a master manipulator. You ‘re like a color-blind person viewing the traffic lights. You know the upper light is “red,” and you know what to do about it, but you have no comprehension of what red really is.

Psychopathic Trait #2: Self-Centered Impulsivity

You act how you want, whenver you wish.  You require stimulation and get bored very quickly. Sometimes you’ll drive intoxicated, steal from stores, start bar fights, humiliate fellow workers, roofie that chicks drink, or torture small animals just for the hell of it.

You’re also completely irresponsible.  You don’t need to pay money back.  You don’t go to work if you don’t want to.  You may have a dishonorable discharge from the army.

Finally, you are very impulsive.  You’ll quit a job, break relationships, drop out of study and have sex with many partners as you want, even if you’re in a relationship.  Why?  Because you want to.  But this impulsivity also means you’re more likely to die in a violent accident, commit suicide, or get killed.

Psychopathic Trait #3: Low Autonomic Arousal

Your physiology is quite different from non-psychopathic people.  Your resting heart-rate is lower, your skin temperature is lower, and the beat-to-beat changes in your heart-rate are not the same as the rest of the sheeplike population.

You’re cool as can be, even when others panic.  When your girl is freaking out, this is when you are at your best. Your heart rate decreases when arguing with and beating up your partners.  The pinacle of this was Hannibal Lechter – who’s heart rate never broke 85 even as he attacked a girl.
So here is the best example of psychopathy I’ve seen.

Eric Cartman from South Park.  Cartman is a true psychopath.