The externalizing scale includes two components: the aggression scale, consisting of 20 items (e.g. “Cruelty, bullying, or meanness to others”, “Screams a lot”, “Threatens people”); and the delinquency scale, consisting of 13 items (e.g. “Swearing or obscene language”, “Steals outside the home”, “Uses alcohol or drugs”). Items are scored according to the point values 0 (“not true”), 1 (“sometimes or somewhat true”), or 2 (“very or often true”). Cronbach’s alpha values for scores of delinquency, aggression, and externalizing ranged from 0.92–0.96 for maternal reports, 0.79–0.89 for teacher reports, and 0.90–0.92 for self-reports. An individual’s score on each of the three scales is simply the sum of the points for each item on the scale; and the externalizing score is the sum of the aggression and delinquency scores. We also conducted secondary analyses examining each of the subscales separately.
