People with sound social judgment can turn into misfits after the frontal lobes of their brains are damaged--but studies have shown that they still know what moral behavior is, even if they can't abide by it. Now researchers report that some children who suffer head injuries at a very young age may never be able to comprehend the rules of society at all.
Children's brains are usually more resilient than adults'; if a child's language centers are damaged, for instance, it can still learn to speak by drawing on other brain areas. Likewise, two patients studied by neuroscientist Antonio Damasio and his colleagues at the University of Iowa in Iowa City at first seemed to recover well from brain traumas. Both children--a girl who was run over by a car at 15 months, and a boy who had a tumor removed at 3 months--had normal IQs and both were raised in stable families. But their lives were marked increasingly by disruptive behavior, stealing, risky sex, angry outbursts, poor financial judgment, and a lack of guilt or compassion--a behavior pattern sometimes seen in people who suffer from orbito-frontal lobe damage as adults, for instance after a stroke.
Using magnetic resonance imaging (MRI), Damasio's team confirmed that the patients, now both in their 20s, had suffered damage to their prefrontal cortex. The researchers then put them through a series of tests assessing vocabulary, arithmetic, and spatial skills--on all of which they did just fine. But as the researchers report in the November Nature Neuroscience, the patients failed miserably when faced with tests that require moral judgment or social reasoning.
One test, the Kohlberg Moral Judgment Task, presents moral dilemmas such as whether one should steal medicine to help a dying spouse. Whether the person answers yes or no is irrelevant; what counts is the reasoning that supports the decision. Most people, including patients whose frontal lobes were damaged in adulthood, base their decision on what they think other people or society would consider right. But the patients with childhood injuries reasoned much like 9-year-olds: most of all, they tried to avoid punishment. The prefrontal cortex is crucial for learning ethical behavior, says Damasio. The findings show that other parts of the brain can't take over when it fails.
"The idea that kids don't learn [moral reasoning] is interesting," says neurologist Robert Knight of the University of California, Berkeley. The study, he says, illustrates a "hidden epidemic" among children with head injuries whose "number one long-term problem is social integration."