Mammals live in groups for protection from predators, but group life is frustrating. Other mammals get the good bananas and mating opportunities. When things go your way, your brain releases serotonin. It feels good, which motivates your brain to do things that stimulate more. You have inherited a brain that cares about its status in a herd or pack or troop, though you would never consciously think this. Your neurochemical ups and downs make sense when you understand the mammal brain.