How television can be harmful for toddlers - even when they're not watching it

Parents who leave the television on all day are stunting the development of their babies and toddlers, a study claims.

Psychologists say that young children find it 'significantly harder' to concentrate if a TV is on in the background  -  even if they appear to pay little attention to it.

The findings are thought to be true for children aged one, two and three.

Dr Marie Evans Schmidt, who carried out the research at the University of Massachusetts, said TV was a potentially 'chronic environmental risk factor' affecting most children.

'Parents should limit their young children's exposure to background television,' she said.

The study looked at the effect of television on 50 children. Each child came to a laboratory and was invited to play for an hour.

For half the time a television was on, showing an episode of the U.S. game show Jeopardy! and commercials. For the rest of the session, the television was turned off.

Even though the toddlers appeared to pay no attention to the adult programme, the television disrupted their playing at every age, the scientists reported in the journal Child Development.

When the TV was switched on, the children played for shorter periods and spent less time focused on the toys compared with when the programme was turned off.

In the past few years separate studies have shown excessive TV in the first few years of life can stunt language skills and contribute to bad behaviour and hyperactivity.

Psychologists say that toddlers and babies learn by interacting. While television can be a useful babysitter, it can also hinder progress.

Some child development experts say that television's fast-moving images damage a growing brain, and children watching TV are not spending time with adults or playing with toys.

In 2003 a study found a link between time spent watching television and difficulty in reading.

Last year, a study at Johns Hopkins University found under-fives who watched TV for more than two hours a day were more likely to suffer behavioural problems.

The American Academy of Paediatrics recommends that children under two watch no television and older children are limited to no more than two hours a day.