Moral neurophysiology

One of the traditional divisions in the study of ethics is that between moral philosophy, which studies questions of right and wrong, and moral psychology, which studies the way we think about right and wrong. But as the latter is ultimately grounded in the physical structures of the brain, there is also another field: moral neurophysiology. The most famous example from this field is the "natural experiment" of Phineas Gage, a man who suffered an abrupt change in his personality (and moral sensibilities) after having a three foot long iron bar stuck through his head. Previously regarded as well-balanced, he became

fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires

More recently, scientists have begun probing the physical basis of moral reasoning by sticking people in MRIs or wiring them up to sensors while presenting them with moral dilemmas, in an effort to determine which parts of the brain are active. The results of this are quite interesting [PDF]. Moral philosophy is traditionally strongly Rationalist; both Kantianism and Utiliatarianism are an attempt to derive morality from first principles - in the former case the Categorical Imperative, and in the latter "the greatest good for the greatest number". Emotion is considered a distraction. But when you look at how the brain works, it turns out that emotion plays a significant role in moral reasoning. The authors of the paper linked above reinterpret the tension between the two great ethical systems as reflecting the tension between two parts of our brains: our basic social and emotional responses inherited from our primate ancestors, and our more recently developed facility for abstract reasoning. There's also a comment that Kantian ethics turns out not to be based on "pure practical reason", but on rationalised emotional response (a kind of abstracted "wisdom of repugnance", though with broader and better targets than Kass's revolting little work).

Which gets me round to the subject of my post: an article in Nature entitled "Damage to the prefrontal cortex increases utilitarian moral judgements" [PDF; if you want the graphs you'll need to get hardcopy or hit the databases]. Following the "natural experiment" paradigm, the authors collected a group of people with damage to a specific area of the brain responsible for social emotions, and fed them a series of moral dilemmas [PDF]. The result was a statistically significant increase in "utilitarian" judgements compared to the control groups in "high conflict" scenarios:

(The target group is that labelled "VMPC"; the others are control groups. X-axis scenario numbers do not correspond to those in the file linked above; the Y-axis is the proportion of those saying "yes" to the utilitarian position).

The authors of the paper interpret this as consistent with both emotion and reason being required to produce normal moral judgements, and as showing that the specific area of the brain under study (the ventromedial prefrontal cortex) is a critical component in the emotional aspect of moral reasoning.

None of this of course tells us anything at all about what is good - it only tells us what is, not what ought to be. But it does tell us something very interesting about ourselves and the roots of our moral disagreements, and (if we believe that "ought implies can") the shape that moral theories should take if they are not to demand the impossible.