When someone confronts an oncoming danger, the eyes or ears (or both) send the information to the amygdala, an area of the brain that contributes to emotional processing. When it perceives danger, it instantly sends a distress signal to the hypothalamus.

...

Humans beings are capable of selfish, even cruel behavior. A quick scan of any daily newspaper quickly reveals numerous unkind, selfish, and heinous actions. 

The question then is why don't we all engage in such self-serving behavior all the time? What is it that causes us to feel anoth...