Abnormal fear response at age three raises criminality risk

Children who fail to show a normal fear response to unpleasant noises at the age of three are at heightened risk for adult criminality, according to a new study.

Yu Gao and colleagues studied nearly 1,800 individuals born in 1969 and 1970 on the island of Mauritius. The individuals are participating in the long-term Mauritius Child Health Project.

At the age of three years, participants were tested to see how they responded to unpleasant noises that normally provoke a fear reaction. When the participants were 23 years old, the researchers used official court records to see which participants had committed property crimes, crimes involving drugs, violence-related crimes, and serious driving offenses. (Petty offenses were not included.) Of the original group, 137 subjects had at least one court conviction.

After controlling for social adversity, age, ethnicity, and gender, Gao and colleagues found that “criminal offenders showed significantly reduced electrodermal fear conditioning at age three compared to matched comparison subjects.” They note that two brain regions, the amygdala and the ventral prefrontal cortex (VPC), play key roles in the fear conditioning process.

“The findings are consistent with the hypothesis that poor amygdala functioning early in life, as indicated by poor fear conditioning, increases the risk for criminal offending,” the researchers say, “and they demonstrate that this fear conditioning risk factor for crime is in place early in life and is not explained by social adversity, ethnicity, or gender.” They add that poor connectivity between the amygdala and VPC, rather than localized dysfunction in these brain areas, may underlie the impairments they detected in fear conditioning.

People who lack normal fear responses, the researchers say, are less likely to avoid situations that may lead to future punishment. Normal fear responses also play an important role in the development of conscience.

The findings, the researchers say, highlight the need for improved health care for young children and the importance of reducing exposure to brain-harming toxins during early development. They conclude, “Enhancing the early health environment of young children from ages three to five years with better nutrition, more physical exercise, and cognitive stimulation has been shown both to improve brain functioning six years later . . . and to reduce adult criminal offending by 35%; conceivably it could also improve amygdala functioning.”

The researchers caution, however, that the roots of criminality are complex and that poor fear conditioning cannot be used to predict later offending.