They found that one in four children aged one could recognise pictures of a cat, dog or baby on the screen. By the age of 18 months 96 per cent could do so. But only a ifth of children with Downs syndrome could recognise the images at that age. TV images are more abstract than pictures in books and provide a marker that needs no special equipment or training to record.
Compiled by Diane Spencer with help from the National Children's Bureau