The current study was part of a larger, ongoing longitudinal study investigating the importance of friendship and peer relations in early childhood for subsequent behavioral, emotional and social adjustment. All children from 33 day care centers, across two semi-rural Norwegian communities – situated 30–90 km north of Norway's largest city, Oslo – were invited to participate in the study. Out of an eligible 996 children, 619 children (62% participation rate) were given the active, written consent of their parents/guardians to participate. Ethical clearance for the study was obtained from the respective Norwegian Regional Ethics Committee and the Norwegian Data Inspectorate. As is common in Norwegian semi-rural areas, the sample was exclusively White Caucasian.