Via New Scientist:
We are figuring out how the brain and its chemicals give rise to moral and social values, says Patricia Churchland
WHERE do moral values come from? Not from Plato’s heaven, nor from any other. Aristotle, Confucius and Darwin all recognised valuing as a basic function of biological creatures generally, and moral valuing as a basic function of highly social and intelligent animals like humans. Until very recently, however, science could not explain how brains, built by gene networks interacting with the environment, give rise to morality.
Natural selection being what it is, caring for others must serve the fitness of the animals involved. Evolutionary biologists have developed models to show how this might work, but it is only now that neuroscientists are catching the first glimpses of how altruistic behaviour happens in the brain.
Morality seems to be shaped by four interlocking brain processes: caring, rooted in attachment to and nurture of offspring; recognition of others’ psychological states, bringing the benefit of predicting their behaviour; problem-solving in a social context, such as how to distribute scarce goods or defend the clan; and social learning, by positive and negative reinforcement, imitation, conditioning and analogy. These factors result in the emergence of a conscience: a set of socially sanctioned responses to prototypical circumstances.
Social values, real as they are, depend on an evolutionary modification of the neural circuitry involved in basic survival. In all vertebrates, brain-stem circuitry keeps crucial parameters such as temperature and carbon dioxide and glucose levels within the right range. In order to maintain this homeostasis, the brain deploys motivations such as pain, hunger, thirst and fear, as well the complementary pleasures of food, water, sex and safety.
As the mammalian brain evolved, the homeostasis network enabling “me” to survive expanded its scope to embrace “mine”, at first meaning one’s own helpless offspring. Pain and anxiety responses were triggered by separation or perceived need; pleasure and comfort came with being suckled, licked and cuddled. In some species, additional adjustments in attachment circuitry widened the circle to include mates, kin and others in the group, depending on selection pressures.
At the hub of the neural circuitry of attachment are ancient peptides: oxytocin and its sibling, vasopressin. Along with other reproductive hormones and neurotransmitters, these peptides organise the circuitry in the hypothalamus, the part of the brain stem involved in attachment to “mine”. Though much remains to be discovered, vasopressin seems to be related more to aggressive care, such as defence, while oxytocin dampens fear and anxiety, which feels good and is associated with trust.
The neocortex – the six-layered mantle covering the brain’s hemispheres – is unique to mammals. The high cost of mammalian dependency at birth is offset by the singular advantages of new forms of learning made possible by the neocortex. In primates, the neocortex appears to be responsible for an enhanced capacity to predict others’ behaviour. It also enables more abstract learning and problem-solving, as well enhanced flexibility in impulse control and social skills. These skills paved the way for the emergence of cultural institutions such as trade practices, criminal justice systems and religions – all of which served to regulate trust among non-kin and allow for a wider range of trusting relationships than isolated hunter-gathering groups could offer. In short, the brain’s regulation of attachment and bonding is what makes us want to be together, to care for one another, and to value our family, friends and community. The interplay of our neural and cultural institutions comprises our moral history.
Patricia Churchland is a philosopher of neuroscience at the University of California and the Salk Institute, both in San Diego. Her book, Braintrust: What neuroscience tells us about morality, will be published by Princeton University Press in March 2011