Children who lack a normal fear response are more likely to commit crimes when they grow up, a study published Monday in the American Journal of Psychiatry suggested.
Researchers assessed the "fear conditioning" of nearly 1,800 three-year-olds by measuring skin activity such as sweat secretion, which is part of the fear reflex, after the children had been blasted by a short, loud, unpleasant sound or a neutral tone.
Then, 20 years later, the researchers looked at the official court records of the study participants.
They found that, by the age of 23, 137 of the study participants had committed serious crimes. None of the adults with a criminal record had shown a normal fear response at age three.
Participants who had not committed a crime by age 23, on the other hand, had a normal fear reaction to the loud, unpleasant noise when they were toddlers.
The researchers hypothesized that the tendency to take up a life of crime as an adult was due less to social conditioning, ethnicity or gender, and more to certain parts of the brain not working as they should.
"The findings of this study potentially provide some support for a neurodevelopmental theory of antisocial and criminal behavior," they wrote.
"If crime is in part neurodevelopmentally determined, efforts to prevent and treat this worldwide behavior problem will increasingly rely on early health interventions," the study said.
For instance, prenatal programs to reduce maternal smoking, alcohol and drug consumption have been shown to reduce juvenile delinquency 15 years later, the study said.
And children aged three to five years old who have a good diet, get plenty of exercise and are mentally stimulated show better brain functioning six years later -- and their rate of criminal offending as adults was reduced by 35 percent.
(c) 2009 AFP
Explore further: Study finds interest in the goals you pursue can improve your work and reduce burnout