[DanaC]

From wiki:

It has been theorized that children with imaginary companions may develop language skills and retain knowledge faster than children without them, which may be because these children get more linguistic practice than their peers as a result of carrying out "conversations" with their imaginary friends.[4]
Kutner (n.d.) holds that:
Imaginary companions are an integral part of many children's lives. They provide comfort in times of stress, companionship when they're lonely, someone to boss around when they feel powerless, and someone to blame for the broken lamp in the living room. Most important, an imaginary companion is a tool young children use to help them make sense of the adult world.[5]
Taylor, Carlson & Gerow (c2001: p. 190) hold that:
despite some results suggesting that children with imaginary companions might be superior in intelligence, it is not true that all intelligent children create them.[6]
A long-time popular misconception is that most children dismiss or forget the imaginary friend once they begin school and acquire real friends. According to one study, by the age of seven, sixty-five percent of children report that they have had an imaginary companion at some point in their lives.[7] Some psychologists[who?] have suggested that children simply retain but stop speaking about imaginary friends, due to adult expectations and peer pressure. Few adults report having imaginary friends. Pediatrician Benjamin Spock believed that imaginary friends past age four indicated that something was "lacking" in the child or his environment. Some child development professionals still believe that the presence of imaginary friends past early childhood signals a serious psychiatric disorder.[8][9] Others disagree, saying that imaginary friends are common among school-age children and are part of normal social-cognitive development.[10]