This is a snipit obtained by Delancyplace but ultimately comes from an excerpt from Jonah Lehrer.
"Psychopaths shed light on a crucial subset of decision-making that's referred to as morality. Morality can be a squishy, vague concept, and yet, at its simplest level, it's nothing but a series of choices about how we treat other people. When you act in a moral manner - when you recoil from violence, treat others fairly, and help strangers in need - you are making decisions that take people besides yourself into account. You are thinking about the feelings of others, sympathizing with their states of mind.
"This is what psychopaths can't do. ... They are missing the primal emotional cues that the rest of us use as guides when making moral decisions. The psychopath's brain is bored by expressions of terror. The main problem seems to be a broken amygdala, a brain area responsible for propagating aversive emotions such as fear and anxiety. As a result, psychopaths never feel bad when they make other people feel bad. ... Hurting someone else is just another way of getting what he wants, a perfectly reasonable way to satisfy desires. The absence of emotion makes the most basic moral concepts incomprehensible. G. K. Chesterton was right: 'The madman is not the man who has lost his reason. The madman is the man who has lost everything except his reason.'
"At first glance, the connection between morality and the emotions might be a little unnerving. Moral decisions are supposed to rest on a firm logical and legal foundation. Doing the right thing means carefully weighing competing claims, like a dispassionate judge. These aspirations have a long history. The luminaries of the Enlightenment, such as Leibniz and Descartes, tried to construct a moral system entirely free of feelings. Immanuel Kant argued that doing the right thing was merely a consequence of acting rationally. Immorality, he said, was a result of illogic. ... The modern legal system still subscribes to this antiquated set of assumptions and pardons anybody who demonstrates a 'defect in rationality' - these people are declared legally insane, since the rational brain is supposedly responsible for distinguishing between right and wrong. If you can't reason, then you shouldn't be punished.
"But all of these old conceptions of morality are based on a fundamental mistake. Neuroscience can now see the substrate of moral decisions, and there's nothing rational about it. 'Moral judgment is like aesthetic judgment,' writes Jonathan Haidt, a psychologist at the University of Virginia. 'When you see a painting, you usually know instantly and automatically whether you like it. If someone asks you to explain your judgment, you confabulate ... Moral arguments are much the same: Two people feel strongly about an issue, their feelings come first, and their reasons are invented on the fly, to throw at each other.'
"Kant and his followers thought the rational brain acted like a scientist: we used reason to arrive at an accurate view of the world. This meant that morality was based on objective values; moral judgments described moral facts. But the mind doesn't work this way. When you are confronted with an ethical dilemma, the unconscious automatically generates an emotional reaction. (This is what psychopaths can't do.) Within a few milliseconds, the brain has made up its mind; you know what is right and what is wrong. These moral instincts aren't rational. ...
"It's only after the emotions have already made the moral decision that those rational circuits in the prefrontal cortex are activated. People come up with persuasive reasons to justify their moral intuition. When it comes to making ethical decisions, human rationality isn't a scientist, it's a lawyer. This inner attorney gathers bits of evidence, post hoc justifications, and pithy rhetoric in order to make the automatic reaction seem reasonable. But this reasonableness is just a facade, an elaborate self- delusion. Benjamin Franklin said it best in his autobiography: 'So convenient a thing it is to be a reasonable creature, since it enables one to find or make a reason for everything one has a mind to do.'
"In other words, our standard view of morality - the philosophical consensus for thousands of years - has been exactly backward. We've assumed that our moral decisions are the byproducts of rational thought, that humanity's moral rules are founded in such things as the Ten Commandments and Kant's categorical imperative. Philosophers and theologians have spilled lots of ink arguing about the precise logic of certain ethical dilemmas. But these arguments miss the central reality of moral decisions, which is that logic and legality have little to do with anything."
Author: Jonah Lehrer
Title: How We Decide
Publisher: Houghton, Mifflin, Harcourt
Date: Copyright 2009 by Jonah Lehrer
Pages: Kindle Loc. 1922-79