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Last Updated: Saturday, February 17, 2001

brain : The neurobiology of morals
CHARLES JENNINGS
Among the earliest evidence that social and moral decisions have a biological basis was the famous case of Phineas Gage, a railroad worker whose brain was damaged when an iron bar was driven through his skull as a result of a dynamiting accident in 1848. Gage survived the accident, but although his intellect was unimpaired, his personality was transformed from that of a conscientious worker to an irresponsible drifter. After Gage's death, his skull was preserved (it is now in the museum of Harvard Medical School), and a few years ago, it was re-examined by a team of neurobiologists led by Hannah and Antonio Damasio at the University of Iowa. The researchers concluded that Gage had sustained damage to a part of the brain called the prefrontal cortex, and studies of contemporary patients with similar types of damage have confirmed that the prefrontal cortex (in particular a region known as the orbitofrontal cortex) plays an important role in social and moral decision-making.

One surprising result of these studies was that patients with prefrontal damage often retain factual knowledge about social and moral standards; in other words, they can answer questions about hypothetical moral dilemmas, even though they appear unable to apply the knowledge in their own lives. (In one standard test of moral reasoning, for instance, subjects are asked questions such as whether a man should steal a drug to save his wife's life, and are asked to explain the rationale for their decision.) Before they suffered their brain damage, of course, these patients were normal people, and so presumably they had learned about accepted standards of behaviour just like anyone else.

But what would happen if the brain damage occurred in early childhood, before the acquisition of this knowledge? Such cases are very rare, but as reported in the November issue of Nature Neuroscience1, the Iowa group has now examined two patients, both now in their twenties, who incurred prefrontal lesions before the age of 16 months. Both children appeared to make excellent recoveries, but as they grew older, they began to display behavioural problems even more severe than is typical for those with adult lesions; these included stealing, lying, verbal and physical abuse of other people, poor parenting of their illegitimate children, lack of remorse, and failure to make plans for their own futures. There were no obvious environmental explanations for their behaviour; both children grew up in stable middle-class families and had siblings who were socially well-adjusted.

The most striking feature of the early-onset patients was that they were deficient not only in their real-life behaviour but also in their moral reasoning abilities in the laboratory tests. Unlike the adult-onset patients, who had learned about accepted standards before their lesions, it appears that those with lesions in early childhood had never acquired this knowledge.

The authors acknowledge that this is a preliminary study, but they hope that their report will lead to the identification of other cases, and to further insights into the neural basis and developmental origins of moral and social behaviour. They also comment that these patients show many similarities to psychopaths, and may therefore provide a deeper understanding of the biological causes of psychopathy and related disorders.

1.Anderson, S.W., Bechara, A., Damasio, H., Tranel, D. & Damasio, A.R. Impairment of social and moral behavior related to early damage in human prefrontal cortex Nature Neuroscience 2, 1032-1037 (1999). Nature

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