Potential for criminal behavior evident at age 3

NEW YORK Mon Nov 16, 2009 2:19pm EST

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NEW YORK (Reuters Health) - Children who don't show normal fear responses to loud, unpleasant sounds at the age of 3 may be more likely to commit crimes as adults, according to a new study.

Yu Gao and colleagues in the United States and the United Kingdom compared results from a study of almost 1,800 children born in 1969 and 1970 on the Indian Ocean island of Mauritius to criminal records of group members 20 years later.

At age 3, the children were tested to gauge their level of "fear conditioning," or fear of consequences. The idea is that children who associate unpleasant sounds or other unpleasant experiences with fear will be less likely to commit antisocial acts because they will link such experiences with punishments for those acts.

Researchers tested the 3-year-olds' responses to unpleasant noises using a lie detector. When they looked at any criminal records among the participants 20 years later, 137 of them (131 male, 6 female) had at least one criminal conviction.

Compared to almost 300 participants with no criminal records, those 137 participants had a much lower response to the noises at the age of 3.

The findings could link previous studies suggesting that psychopaths and children with behavioral problems at the age of 11 have similar abnormalities in a part of the brain called the amygdala. That structure is largely responsible for directing fear of consequences.

Because this study controlled for social factors such as parents' education, number of parents in the home, socioeconomic status, and family size, biology is the likely reason for the "blunted emotions" registered in some of the 3 year olds, study co-author, Dr. Adrian Raine of the University of York in England, told Reuters Health in a telephone interview.

Still, the researchers warn against reading too much into their findings. The results do not offer a biological way to identify future criminals.

"Crime is clearly a complex construct involving multiple interactions between genetic, brain, family and social influences," they write.

But, they conclude, the findings provide some support for the idea that the potential for antisocial and criminal behavior may be hard-wired in young brains - which means that if the results hold, "efforts to prevent and treat this worldwide behavior problem will increasingly rely on early health interventions."

SOURCE: American Journal of Psychiatry, published online November 16, 2009.

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