Gao et al. (CME, p. 56) present evidence that early brain dysfunction contributes to later antisocial behavior. Learning to associate a cue with a frightening outcome, known as fear conditioning, relies on prefrontal cortex regulation of an amygdala response. Among 1,795 3-year-old children tested for fear conditioning, 137 had convictions for serious offenses by age 23. Noncriminal subjects matched for ethnicity, gender, and social adversity showed normal fear conditioning at age 3, but the children who became criminals showed significantly reduced fear conditioning. Dr. Philipp Sterzer expands on the neurobiology of antisocial behavior in an editorial on p. 1.