TUESDAY, Nov. 17 (HealthDay News) -- Children who are fearless at 3 years of age might just be poised for a life of crime.

According to a new study, poor fear conditioning at the tender age of 3 can predispose that person to break the law as an adult. Yet other factors, such as education of the parents, large family size, nutrition, physical activity, configuration of the household and other elements also play a role, the researchers concluded.

"There's no 100 percent correspondence between conditioning deficits and crime: Not all poor conditioners will become criminals and not all criminals have the early fear conditioning deficits," explained study author Yu Gao, a research associate in the department of criminology at the University of Pennsylvania. His findings are published in the Nov. 16 online issue of the American Journal of Psychiatry.

Specifically, what Gao and his associates set out to determine is whether dysfunction of the amygdala, an almond-shaped mass that resides deep in the human brain and is linked to fear conditioning as well as emotions and mental state, leads to an inherent intrepidness and disregard for the law.

Twenty years ago, the research team tested almost 1,800 children who were 3 years old from Mauritius, an Indian Ocean island off the coast of southeastern Africa, by exposing them to two sets of sounds, one with a short shrill noise, and the other deeper in pitch and with a pleasant tone, and then measuring the children's physical responses through an electrode attached to their index and middle fingers. Sweating upon hearing the loud noise indicated a sense of fear, while no sweat meant the child lacked fear -- that is, had poor fear conditioning.

Two decades later, using court records, Gao and his team tracked down 137 study participants -- 131 males and six females -- who had committed serious crimes involving property, drugs, violence and driving. These individuals had shown an absence of fear during testing at age 3, whereas 274 study participants who had grown to adulthood without a criminal record had displayed typical fear responses.

Experts agreed that the findings don't constitute a cause-and-effect situation, but hailed the study for its longevity and what the work adds to what is known about how childhood factors influence adult behavior.

"Any time you have a 20-year study, that's significant," said Dr. Elissa P. Benedek, an Ann Arbor, Mich.-based psychiatrist who has worked in private practice with children and adults for more than 40 years and is a past president of the American Psychiatric Association.

"It's good for putting another link in the chain in terms of what is early brain dysfunction, and what increases the risk for such behaviors as attention-deficit disorder and criminal activity. It's another link back to whatever we all ready know about early brain dysfunction that may cause problems later in life," Benedek added.

So what do the results mean for individuals with fear conditioning deficits and their loved ones, and for society at large? It's a wake-up call about potential problems, said Gao and other experts in the field. To enhance the proper working of the amygdala, which is believed to reduce criminal behavior in later life, enrichment programs are essential.

In fact, according to Gao, some at-risk children between the ages of 3 and 5 who have benefited from those programs, which include sound nutrition, adequate physical exercise and cognitive brain stimulation, had shown an improvement in brain functioning by age 11 that reduced the chances of criminal behavior by 35 percent 20 years later.

Addressing parental concerns, Benedek added: "Don't be discouraged if your child has early brain dysfunction. It doesn't mean that he or she is going to grow up and be a criminal. The brain can change and grow."

More information

For more on the causes of violent behavior among children, go to the U.S. National Institute of Mental Health.

SOURCES: Yu Gao, Ph.D., research associate, department of criminology, University of Pennsylvania, Philadelphia; Elissa P. Benedek, M.D., adjunct professor, psychiatry, University of Michigan, Ann Arbor, psychiatrist, Ann Arbor, Mich., and past president, American Psychiatric Association; Nov. 16, 2009, American Journal of Psychiatry, online

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