It was the last day of an intense, three-day conference, and Craig Ferris, a neuroscientist who had organized the conference, was exhausted and cranky.
So when someone observed that the research presented at the meeting seemed to indicate that aggressive behavior in both animals and humans is linked more closely to environmental factors–from the womb through early upbringing–than to genetic makeup, Ferris couldn’t resist a caustic joke:
“That’s right. But everyone’s so intent on finding a gene for this or that. They want quick solutions, but there are no quick solutions here. Maybe we could find the gene for poverty, correct it, and then we’d all get rich.”
Ferris, of course, wasn’t serious, but the goal of the conference, which attracted some of the best minds in the field, was dead serious: to bring together the latest research and tackle head-on the issue of what is seeding the rising rate of violence among the nation’s youth.
“For too long, people have been saying (violent individuals) must have inherited their aggressive tendencies,” said neuroscientist Jean King, a colleague of Ferris’ at the University of Massachusetts Medical Center in Worcester. “But the research shows that environment plays a much stronger role.”
The notion that bad parenting, physical abuse and neglect, racism, domestic violence and poverty may play a role in the development of aggression is not a new one. And such factors are certainly not the entire answer, given that some children are able to overcome extraordinary deprivation and thrive.
But for the first time, researchers at the conference on Understanding Aggressive Behavior in Children brought together hard evidence that environmental wounds may leave a lasting imprint on the neurochemical wiring of children’s brains–an imprint that may have disturbing consequences later.
“Early stress has been shown to permanently alter the development of the hormonal and neurochemical system that responds to stress,” King said at the conference, which was sponsored by The New York Academy of Sciences. “In animal studies, these changes have affected later behavior, increasing the risk of aggression in some animals, and this research is suggestive of similar effects in humans.”
King and others acknowledge that such findings are scary because they highlight how very vulnerable young children are to their surroundings. But they also find them hopeful, because environment can be changed to some extent.
Indeed, several researchers reviewed two limited social intervention programs that had, on a small scale, managed to reduce aggressive behavior among groups of children identified as being at high risk of destructive behavior.
The programs targeted very different populations, one from a working-class urban environment in Worcester and another from rural Pennsylvania, but both took an all-inclusive approach toward making key changes in the children’s school, peer and home surroundings. They included, for example, in-class training on conflict resolution and social skills, after-school counseling groups for the children and their parents, home visitations and academic tutoring.
While the interventions did not make the children less destructive at home, they did improve behavior at school. And more importantly, the parents, many of them overwhelmed by the demands of single parenting and poverty, felt the interventions helpful and wanted more.
The parents’ reaction is a crucial indicator of success, say social scientists, many of whom concur with Rashaan Allen, a 22-year-old from Dorchester who worked on the Boston Violence Prevention Project, a city program. Commenting on the problem of youth violence last year, Allen said: “It all starts with a messed-up family scene.”
The findings show that the mess-up can begin even before birth and has strong roots in a stressful early environment and the emotional capabilities of individual parents.
It also has to do with the temperaments of the children themselves. There is, for instance, evidence that some children are more temperamentally or genetically disposed to be impulsive, fearless risk-takers. As infants, they have lower resting heart rates and are generally slower to start sweating and show other physiological reactions to stress. As a result, they may be more adventuresome and likely to venture into trouble than children who are quicker to panic.
But not all such individuals turn to a life of crime; researchers say it depends on the way the children are raised.
“Whether or not an under-aroused individual turns to crime to obtain their `arousal jag’ in life may be a function of the social milieu,” said Adrian Raine, a research psychologist at the University of Southern California who reported these findings at the New York conference. “For example, those . . . exposed to delinquent peers or who have antisocial parents as models may turn to crime to increase arousal levels, whereas those who have a high IQ and are brought up in a non-criminogenic environment may obtain their stimulation from a career in politics or academic research.”
Interestingly, there is evidence that it is not just the social milieu that makes a difference. In one study, researchers found that youths whose mothers smoked more than a pack of cigarettes a day while pregnant exhibited more antisocial behavior than those whose mothers who came from similar socioeconomic backgrounds but didn’t smoke. And in animal research, King and her colleagues have found a biochemical mechanism that might explain this curious link between early exposure to nicotine and later aggression.
“If you treat an animal with higher nicotine prenatally, there’s a blunting in their stress response that may in fact predict later aggression,” King reported. In both physical and psychological terms, “how these animals act in adulthood is totally guided by what happened early in their infancy.”
The same turns out to be true of rhesus monkeys. Researchers at the University of Wisconsin compared monkeys that were raised by their mothers with others that spent their early life not with their mothers but with same-age peers.
They found in the latter group lower levels of serotonin, a neurotransmitter that has been found in other studies to inhibit aggression. They also found that the monkeys reared with their peers were more aggressive than those kept with their mothers, particularly after being separated from their friends. Some were extremely aggressive.
“These monkeys all started out with normal biochemical systems,” noted psychologist Gary Kraemer of the University of Wisconsin, who led the study. “The biochemical changes we found are the effect of a particular rearing condition.”
Similarly, mild-mannered hamsters that were threatened and attacked when young not only had lasting changes in their brain circuitry for serotonin and vasopressin, another neurotransmitter that regulates aggression; as adults, they were more likely to attack and bully younger hamsters put in their cage.
“We found that the stress of social subjugation actually affects the biochemistry of the brain,” said Ferris, who led this research. “And these chronically stressed animals then turned on smaller animals.”
Ferris and his colleagues found that serotonin levels in the bullying hamsters were lower than normal, while vasopressin levels were higher, suggesting the two systems work together in controlling aggressive behavior.
Other researchers have also found changes in the biochemistry of humans abused in childhood, but in different neurochemical and hormonal systems that regulate reactions to stress.
“We are finding a number of neurochemical and hormonal systems in the body that are involved in modulating aggression,” said Efrain Azmitia, a psychologist at New York University. “In fact, it’s amazing how redundant a system we have for controlling aggression.”
While scientists have yet to nail down the neurochemical “recipe” for aggressive behavior, a growing body of evidence supports the link between early deprivation and later violence. In one study, Cathy Spatz Widom, a psychologist at the State University of New York in Albany, identified 908 children who had been victims of physical abuse or life-threatening neglect that led to the filing of criminal charges. Tracking the children over the next 20 years, she found that those who had been childhood victims of abuse had double the rate of arrests for violent crimes than a comparison group. Those who had been victims of neglect had 50 percent more arrests.
As Widom’s study showed, however, not all abused children had arrest records, and at the conference Widom cited several factors that appear to protect these survivors from violent behavior: a high IQ, a high reading ability, having a significant caregiver in their lives (not necessarily a parent); and having lived with both parents at some point.
Because IQ is a fluctuating measure of intelligence and is influenced by academic gains, Widom said, her findings speak to the importance of making sure youngsters who have been abused or neglected receive help in school.
King concurred. “These findings indicate we need many more early intervention strategies, both in the home and at school.”
