Cognitive development

Children as young as 3 years old will step in to right the wrong if they see someone being mistreated, a study finds. But they aren't as keen as 5-year-olds to dole out punishment.

Individual differences in the brain's working memory could help explain why some teens are especially impulsive about sex. Having engaged parents helps reduce the risk.

Giving the newborn one last boost of blood from the placenta may help increase social and motor skills at age 4, a study finds. Earlier studies have found health benefits in infancy.