Study: Major moral decisions use the reward circuitry to manage uncertainty

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There is more here than meets the eye. What this study suggests is that we use our reward circuitry for moral decisions. Our reward circuitry is a big part of our moral compass. The abstract is below the article. It mentions 3 parts of the brain used in moral decsions - all parts of the reward circuitry. (the ventral striatum is the nucleus accumben - which is considered THE reward center.
So - what affects our reward circuitry then affects our moral compass - because they are inseparable

MAJOR MORAL DECISIONS USE GENERAL PURPOSE BRAIN CIRCUITS TO MANAGE UNCERTAINTY
August 25th, 2010 in Medicine & Health / Neuroscience

(PhysOrg.com) -- Scientists at Harvard University have found that humans can make difficult moral decisions using the same brain circuits as those used in more mundane choices related to money and food.
These circuits, also found in other animals, put together two critical pieces of information: How good or bad are the things that might happen? What are the odds that they will happen, depending on one's choice? The results suggest that complex moral decisions need not rely on a specific "moral sense."

Amitai Shenhav and Joshua D. Greene of Harvard's Department of Psychology present the findings this week in the journal Neuron.

"It seems that our capacity for complex, life-and-death decisions depends on brain structures that originally evolved for making more basic, self-interested decisions about things like obtaining calories," says Shenhav, a doctoral student in psychology at Harvard. "Many of the brain regions we find to be active in major moral decisions have been shown to perform similar functions when people and animals make commonplace decisions about ordinary goods such as money and food."

Some researchers have argued that moral judgments are produced by a "moral faculty" in the brain, but Shenhav and Greene's work indicates that at least some moral decisions rely on general mechanisms also used by the brain in evaluating other kinds of choices.

"Research in neuroeconomics has identified distinct brain structures responsible for tracking the probability of various outcomes, the magnitude of various outcomes, and for integrating these two kinds of information into a decision," says Greene, an assistant professor of psychology at Harvard. "Our work shows that the parts of the brain people use for this last task -- combining assessments of outcome probability and magnitude into a final decision -- closely coincide with the brain regions we use daily when deciding how to spend money or choose foods."

Using real-time brain imaging, Shenhav and Greene presented 34 subjects with hypothetical choices between saving one life with certainty or saving several lives, but with no guarantee that this latter effort will succeed. The experiment systematically varied the number of lives at risk and the odds of success.

The authors found that a brain region called the ventromedial prefrontal cortex tracked the "expected moral value" of the uncertain option, integrating information about the number of lives to be saved and the probability of saving them. Other brain regions separately tracked outcome magnitude and outcome probability.

The work advances our understanding of how people make decisions affecting the lives of others. Many of the most consequential such decisions are made by policymakers: In some cases, a single choice can impact thousands of lives.

"For example, how did President Truman decide to deploy nuclear weapons against Japan in 1945, ending World War II, but at an enormous cost?" asks Greene. "Our results suggest that such decisions employ the same basic mechanisms our brains use when we evaluate whether it's worth spending a few hundred dollars for an extended warranty on a new car."

Truman's historic decision shows parallels to ones made by ordinary people every day. It involved trade-offs among outcomes of different magnitude: How many lives would be lost? How many saved? Second, Truman's decision was made under uncertainty. He could, at best, assign probabilities to possible outcomes.

Likewise, ordinary decision-makers must compare the relative sizes of costs and benefits, as when a car buyer balances the cost of a warranty against the cost of repairs. The consumer doesn't know at the outset whether she will have to pay for expensive repairs down the road.

"Truman, like ordinary decision-makers, had to put information about probability and magnitude together to reach a decision," Shenhav says. "And like the car buyer, Truman likely relied on his ventromedial prefrontal cortex to evaluate his options."

Here's the actual research abstract
Moral Judgments Recruit Domain-General Valuation Mechanisms to Integrate Representations of Probability and Magnitude
Amitai Shenhav1, , and Joshua D. Greene1

Highlights
Complex moral decision making parallels complex economic decision making
► vmPFC encodes subjective representations of expected value in life-and-death judgment
► Insula activity tracks differences in behavioral sensitivity to probability of death
► Ventral striatal activity tracks individual sensitivity to expected moral value.

Summary
Many important moral decisions, particularly at the policy level, require the evaluation of choices involving outcomes of variable magnitude and probability. Many economic decisions involve the same problem. It is not known whether and to what extent these structurally isomorphic decisions rely on common neural mechanisms. Subjects undergoing fMRI evaluated the moral acceptability of sacrificing a single life to save a larger group of variable size and probability of dying without action. Paralleling research on economic decision making, the ventromedial prefrontal cortex and ventral striatum were specifically sensitive to the expected moral value of actions, i.e., the expected number of lives lost/saved. Likewise, the right anterior insula was specifically sensitive to outcome probability. Other regions tracked outcome certainty and individual differences in utilitarian tendency. The present results suggest that complex life-and-death moral decisions that affect others depend on neural circuitry adapted for more basic, self-interested decision making involving material rewards.