Even six-year-olds who believe Santa Claus is a real person are shrewd enough to realise that Superman cannot actually fly, says Dr Maire Messenger Davies, a London-based academic who interviewed 82 middle-class American children aged six to 11 about their television viewing.
Furthermore, only one in eight of the six and seven-year-olds had been fooled into thinking that programmes such as The Cosby Show were filmed in a real house, she told the conference.
These figures might reassure those who argue that the ability to tell the difference between reality and fantasy reduces television's potential harm. But Dr Davies, of the School of Media, London Institute, said that this was a simplistic conclusion to draw as children can still be upset by things they know to be fantasy.
"What the study suggests is that children in this age group can demonstrate extensive knowledge and critical insights about the workings of the medium, " she said. "Mass media experiences are sometimes seen as inimical to formal education, but they could be used to provide opportunities to extend children's critical capacities and reasoning skills."