From the Family Research Council’s Mapping America Project:
Children who live with both biological parents or two adoptive parents are more socially developed than those who do not.
According to the National Survey of Children’s Health, children who live with both biological parents or two adoptive parents score higher on the social development scale (50.8) than children who live within other family configurations (48.2), such as with their father only or foster parents.[3] In between are those who live with a biological parent and a stepparent (48.5) and those who live with single mothers (49.0).[4]
Positive social development is shown by behaviors such as getting along with other children, showing respect for teachers and neighbors, trying to understand other people’s feelings, and trying to resolve conflicts between people.
Wow…I'm surprised the max difference is only 48.2 to 50.8.