The stories were scored for both recall and quality of the story, including whether they mentioned character's names and used dialogue.

In the realistic storytelling task, children were asked to talk about a recent outing, such as a trip to the beach. Again, the stories were scored on recall and quality indicators such as information about time and place.

While children were not found to differ in their sheer vocabulary levels, those with invisible companions told higher-quality stories, both about fictional and real events.

'Most importantly, the children with imaginary friends tailored their stories to the task. For fictional stories, they included more dialogue. For realistic stories, they provided more information about time and place compared to children without imaginary friends,' said Reese.

These findings appeared in the latest issue of Child Development.