|Vol. 6, No. 1, 2000 Page 3|
It's well known that adults who suffer damage to the prefrontal cortex of the brain can undergo dramatic personality changes, becoming irresponsible, impulsive, and socially inept. New research by Antonio Damasio and colleagues reveals that similar lesion ns occurring during infancy can cause much more severe impairment of moral and social behavior-impairment similar in some ways to that seen in psychopaths.
Damasio and colleagues studied two young adults, both of whom suffered prefrontal cortex lesions in infancy (one due to an accident and the other due to a tumor). In both cases, the subjects appeared to have recovered fully from their brain lesions, but l later exhibited a wide range of antisocial and amoral behaviors.
The 20-year-old female subject studied by Damasio et al. was intelligent and academically competent, but she stole from her family and other children, abused other people both verbally and physically, lied frequently, and was sexually promiscuous and comp pletely lacking in empathy toward her illegitimate child. In addition, the researchers say, "She never expressed guilt or remorse for her misbehavior. She blamed her misdeeds and social difficulties on other people." The second subject, a 23-year-old male e, was unmotivated, slovenly, and financially reckless, "engaged in poorly planned petty thievery," lied frequently, assaulted other people physically, and was sexually promiscuous. He too conceived an illegitimate child in whom he showed no interest, and d, like the other subject, he showed no guilt or remorse for his harmful behavior.
Damasio and colleagues note that their subjects' behavior problems could not be traced to environmental factors, because both came from loving, stable, middle-class homes and had devoted parents. In addition, both patients had well-adjusted siblings who e exhibited no behavior problems.
Both of the subjects performed well on measures of intellectual ability, but, like people with adult-onset prefrontal cortex damage, they were socially impaired, failed to consider future consequences when making decisions, and failed to respond normally to punishment or behavioral interventions. "Unlike adult-onset patients, however," the researchers say, "the two patients had defective social and moral reasoning, suggesting that the acquisition of complex social conventions and moral rules had been impa aired." While adult-onset patients possess factual knowledge about social and moral rules (even though they often cannot follow these rules in real life), Damasio et al.'s childhood-onset subjects appeared unable to learn these rules at all. This may expl lain, the researchers say, why their childhood-onset subjects were much more antisocial, and showed less guilt and remorse, than subjects who suffered similar damage in adulthood.
The two childhood-onset subjects resembled psychopaths in their lack of empathy, their lack of remorse, and their destructive behavior. However, Damasio and colleagues say, "The behavior of our patients differed from the typical profile of psychopathy in that our patients' patterns of aggression seemed impulsive rather than goal-directed, and also in the highly transparent, almost child-like nature of their transgressions and their attempts to cover them."
"Impairment of social and moral behavior related to early damage in human prefrontal cortex," Steven W. Anderson, Antoine Bechara, Hanna Damasio, Daniel Tranel, and Antonio R. Damasio, Nature Neuroscience, Vol. 2, No. 11, November 1999, pp. 1032-10 037. Address: Antonio R. Damasio, Department of Neurology, Division of Behavioral Neurology and Cognitive Neuroscience, University of Iowa College of Medicine, Iowa City, IA 52242, firstname.lastname@example.org.