Participants and Procedure Purposeful and convenience sampling was used in the actual study. Elementary school from five regions (New Taipei City, Hsinchu, Tainan, ZhangHua, and YunLin) in Taiwan were randomly sampled from a list of all elementary schools. Thirty-six classes in Grades 4 to 6 were selected from six elementary schools. One hundred and forty five students (boys, N = 84; girls, N = 96) were participated in the actual study. All participants came from families with two children whose age difference was within four years (either older or younger than the participant). Measures The Forms and Functions of Aggression Questionnaire. Relational aggression was assessed by The Forms and Functions of Aggression Questionnaire (Little …show more content…
All participants were asked to assess the degree to which their mothers treated the children differently (Daniels & Plomin, 1985). This scale was developed based on the Distributive Justice Viewpoint. Individual tends to observe and make judgment toward parental treatment. SIDE includes nine items that assess two main factors: differential affection and differential control. The differential affection scale measures maternal pride, interest, favoritism, enjoyment, and sensitivity (e.g., our mother enjoys doing things with us). The differential control scale measures maternal strictness, punishment, blame, as well as discipline (e.g., our mother punishes us for our misbehavior). Participants were required to rate on a five-point Likert scale (1 = applies more to my sibling, 2 = applies a little more to my sibling, 3 = applies equally to me and my sibling, 4 = applies a little more to me, 5 = applies more to me) about how their mother treats them compared to their siblings. The reliabilities for affect scale and control scale were ∝ =.84, and. 79 respectively (Kowal, Krull, &Kramer, 2006). In order to assess the degree of parental differential treatment, score in each items was recoded as an absolute score. For instance, 1 and 5 were recoded as 2 which indicates that the maternal treatment is very different; 2 and 4 were recoded as 1 which indicates that the maternal treatment is slightly different; and 3 was recoded as 0 which indicates a similar degree of maternal treatment. Higher scores indicated higher affection or control from their mothers, while lower scores indicated otherwise. Mid score indicated that siblings were treated equally in the