Children's friendship quality trajectories from middle childhood to early adolescence and prediction from sex.

We investigated the development of children's self-reported positive (Companionship and Recreation, Validation and Caring, Help and Guidance, Intimate Disclosure, and Conflict Resolution) and negative (Conflict and Betrayal) friendship quality from the third to sixth grades using The National Institute of Child Health and Development (NICHD) Study of Early Child Care and Youth Development data (NICHD SECCYD; n = 1,364; M age = 9.03 years; 51.70% boys at recruitment). Consistent with expectations, growth models suggested that children reported higher positive, and lower negative, friendship quality with age. Boys had significantly lower positive friendship quality at third grade and slower increases than girls. Boys had slower decreases in negative friendship quality than girls. It is possible that different social orientations explain sex differences in friendship quality trajectories. Further research is needed to explore other factors that might account for individual differences in friendship quality trajectories.