The parent–child conflict scale on the Parental Environment Questionnaire (PEQ; Elkins et al. 1997) was administered to assess conflict in each parent–child relationship (12 items; e.g. ‘My parent often criticizes me’; ‘My parent and I often get into arguments’). Mothers and fathers individually rated their relationships with each of their participating children, while children individually rated their relationships with their mother and their father. Items were the same for parents and children, with alterations in wording appropriate for particular raters. Each item was rated on a four-point scale (1 = definitely true; 2 = somewhat true; 3 = somewhat false; 4 = definitely false). The PEQ was read to twins with reading levels under 5th grade (as assessed via a brief reading screen; Torgesen et al. 1999) to assure comprehension of the items. The conflict scale displayed good internal consistency reliability, with α’s between 0.74 and 0.87 across all age groups (i.e. 6–8 and 9–11 years old) and individual informants (i.e. parents and children). Maternal and paternal reports of conflict were available for 990 and 857 twins, respectively. Child reports
