It is a very important step to consider the variables that affect sibling relationships together. This study aimed to determine the effects of the variables Birth Order (First, Middle, and Last), Gender (Female, Male), and Number of Siblings ("two or three" and "four or more"), which have been suggested to affect sibling…

The present study investigated children's internal state language during play with their sibling and friend across early and middle childhood. Specifically, the category type of internal state language (e.g., cognitions and goals), referent (e.g., own and other), and associations with children's birth order were examined. A total of 65 (T1: Time…

Longitudinal data were obtained from 157 children aged 3 years 3 months to 5 years 6 months at Time 1. At Time 2 these children had aged an average of 12 months. Theory of mind (ToM) and executive functioning (EF) were measured at both time points. Results suggest that Time 1 ToM scores predict Time 2 EF scores. Detailed examination of sibling…

Investigates the characteristics of the intrafamily environment that change the intellectual environment of the children and interact with the factor of birth order. Concludes that the effect of birth order is linked: (1) with the gender configuration of sibling relationships; and (2) with various cognitive and personal characteristics of the…