I'm referencing this nytimes essay on U of Virginia psychologist John Haidt's The Happiness Hypothesis: Finding Modern Truth in Ancient Wisdom. Harvard's Steven Pinker says, “I’m a big fan of Haidt’s work.”
Haidt thinks evolution has equipped persons with two moral systems: 1) moral intuition; and 2) moral judgment. #1 is the sense that something is right or wrong. #2 is giving an explanation for what moral intuition has intuited ("decided"). Haidt "likens the mind’s subterranean moral machinery to an elephant, and conscious moral reasoning to a small rider on the elephant’s back. Psychologists and philosophers have long taken a far too narrow view of morality, he believes, because they have focused on the rider and largely ignored the elephant."
That's a nice analogy, and interesting.