The PPD scores ranged from 13 to 58, with a mean PPD score of 18.24 and a standard deviation of 6.62. Results of a t-test demonstrated that males perceive their peers to be significantly more delinquent than females (male: mean = 18.58, S.D. = 6.61; female mean = 17.94, S.D. = 6.62; t = 2.378, p = 0.02). However, there were no significant sex differences in the magnitude of genetic and environmental influences on PPD. For both males and females the heritability of PPD was estimated at 0.21 (0.04-0.39), shared environment 0.40 (0.23-0.55) and non-shared environment 0.39 (0.34-0.44). Button et al. (2006) reported a heritability of 0.40, a shared environment estimate of 0.19, and a non-shared environment estimate of 0.41 for DV (i.e. assuming no rGE or GxM). However, the current study has been expanded to include 12-year-olds (the previous analysis only included those aged 13 years and older), resulting in slightly different standardized parameter estimates of 0.32 (0.15-0.50) for a2, 0.28 (0.11-0.53) for c2, and 0.41 (0.38-0.46) for e2. As there was insufficient power with this sample to detect
