This study examined the physiological and behavioral profile of a group of clinically referred boys (ages 8-12 years) with severe conduct problems. Cerebral EEG asymmetry, fear potentiated startle and cardiac functioning were assessed along with maternal reports of severe antisocial behavior and behavioral measures of reward seeking, reward dominance, and laboratory aggression. Drawing on research seeking to extend the concept of psychopathy to younger populations, this study implemented the Antisocial Process Screening Device (APSD; Frick & Hare, 2001) an assessment instrument designed to assess psychopathic characteristics in children. Two groups of clinically referred children with externalizing problems were screened from an outpatient psychiatry clinic, one with elevated scores on the APSD (> 25) and a second group with externalizing problems but without elevated scores on the APSD (< 20). A third group of comparison boys was recruited from the community.

Findings did not support a fear deficit specific to boys with APSD elevations, but rather suggested under some conditions these children may have exaggerated startle reactivity. High APSD boys sought rewards to a greater extent than other clinically referred externalizing boys on a point-subtraction game, but not more than comparison boys. The point-subtraction game did not differentiate groups of boys on aggressive responding. Boys with elevated APSD scores were rated as displaying greater overt and covert antisocial behavior problems than clinically referred boys without high APSD scores.

A dimensional perspective was explored as an alternative to the categorical (subtyping) approach. When disruptive behavior disorder measures were treated as continuous dimensions, the APSD was not the criterion most strongly accounted for by predictor variables. Broadband externalizing behavior problems were more strongly associated with indicators of approach motivation and fear reactivity, including resting frontal asymmetry and startle change during threat and safety. Similarly these variables were associated with an oppositional defiant symptom dimension. Regression analyses that focused specifically fear reactivity and insensitivity to punishment for predicting callous-unemotional traits indicated that the door-opening task, startle change during safety and harm avoidance each accounted for unique variance.