Most people have it to a small extent (it's a feature present all across the animal kingdom, after all), but in psychopaths it is exacerbated.
Sorry, no references. Just a speculation that seems strongly consistent with what I know so far about them.
This is a thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. The previous "stupid" questions thread is at almost 500 questions in about a month, so I think it's time for a new one.
Also, I have a new "stupid" question.