For the study, the researchers from University of Massachusetts looked at 50 children ages 1, 2, and 3. Each child came to a lab with a parent and was invited to play for an hour with a variety of age-appropriate toys.
For half the time, a television was on in the room, showing an episode of the adult game show Jeopardy!, with commercials; during the other half hour, the TV was turned off.
The team found that background TV disrupted toy play of the children at every age, even when they paid little attention to it.
When the television was on, the children played for significantly shorter periods of time and the time they spent focused on their play were shorter, compared to when the TV was off.
"Background TV, as an ever-changing audiovisual distractor, disrupts children's efforts to sustain attention to ongoing play behaviours," said Marie Evans Schmidt, who is now a research associate at the Center on Media and Child Health at Children's Hospital Boston and is the lead author of the study.
"Background TV is potentially a chronic environmental risk factor affecting most American children. Parents should limit their young children's exposure to background television," she added.
The study is published in the July/August 2008 issue of the journal Child Development.