TABLE 3.

Measures of Social and Biological Risk Factors for Externalizing Behavior Problems of Twins in USC-RFAB across Waves 1–5

	Wave 1	Wave 2	Wave 3	Wave 4	Wave 5
Age (in years) of twins	9–10	11–13	14–15	16–18	19–20
N twin pairs	N = 614	N = 445	N = 504	N = 605	N = 625
Peers, activities, and social risk factors
Peer Delinquency and SU*	Y P	Y P	Y P	Y P	Y P
Peer Victimization*	YT	Y T	Y T	Y T	—
Romantic Relationships*	—	—	Y	Y	Y
Parental Monitoring (Kerr & Stattin, 2000)	Y P	Y P	Y P	Y P	—
Parent to Child Affect (adapted from Deater-Deckard, 1996)	Y P	Y P	Y P	Y P	Y P
Conflict Tactics Scale (Harsh Discipline/Marital Conflict; Straus et al., 1998))	Y P	Y P	Y P	Y P	Y P
Socioeconomic Status (SES; [48])	P	—	P	—	Y
Psychophysiology (Autonomic)
Arousal (Heart rate and skin conductance, during rest) (Lang & Hnatiow, 1962)	Y	Y	Y	Y	Y
Orienting (Raine et al., 1990)	Y	Y	Y	Y	Y
Skin conductance responses (during rest and tasks) (Lykken, 1957)	Y	Y	Y	Y	Y
Vagal tone/heart rate, during rest and tasks (Porges, 1995; Lang & Hnatiow, 1962)	Y	Y	Y	Y	Y
Anticipatory fear (Countdown Task; Hare, 1965)	Y	Y	Y	Y	Y
Affective (startle) response (Patrick et al., 1993)	Y	Y	Y	Y	Y
Stressor (Jern et al., 1991; McNair et al., 1982)	—	—	Y	Y	Y
Fear conditioning (Hare, 1965, 1978)	—	—	—	Y	Y
Electrocortical (EEG and ERP)
EEG power spectra	Y	—	—	—	Y
Go/NoGo (ERP – P300; Halperin et al., 1991)	Y	—	—	—	Y
Oddball (ERP – P300; Kiehl et al., 1999)	Y	—	—	—	Y
Neuropsychological and cognitive tasks
Empathy Quotient (Baron-Cohen & Wheelwright, 2004)	—	—	Y	Y	Y
Iowa Gambling Task (IGT; Bechara et al., 1994)	—	Y	Y	Y	Y
Impulsivity/inattention (Go/NoGo Task; Halperin et al., 1991)	Y	Y	Y	Y	Y
Wechsler Abbreviated Scale of Intelligence (WASI; Wechsler, 1999)	Y	—	—	—	Y
Executive function (Grant & Berg, 1948; Porteus, 1965; Reitan & Wolfson, 2004)	Y	Y	Y	Y	Y
Woodcock Johnson — Reading Ability/Comprehension (Woodcock & Mather, 1989)	Y	—	Y	—	Y

Note: Y = youth report; P = parent report; T = teacher report;

^*= developed specifically for this study.