Dr Shari Barkin, an American paediatrician visiting New Zealand for the Brainwave Trust, says preschool children who watch TV for more than one hour a day, and older children watching for more than two hours, are more likely to develop aggression, learning and attention deficit disorders.
She has just led a $3 million, five-year experiment across the United States, Canada and Puerto Rico in which paediatricians cut children's TV viewing by an average of 45 minutes a day.
They used a technique called ‘‘motivational interviewing'', in which they asked parents whether they were concerned about their children's TV viewing, talked about what could be done about it, and gave them timers to help enforce viewing time limits.
They also talked about other things that might make the children less aggressive, such as locking up guns and changing discipline methods from smacking to ‘‘time out''. They provided locks for the guns and encouraged parents to use the timers for time out as well as TV watching.
The effects on discipline were less clear because only 5% of the parents admitted using corporal punishment even before the experiment, a figure which fell to 2.9% afterwards.
‘‘So yes, that was effective, but it makes me wonder how we capture that data,'' Dr Barkin said. ‘‘I think it's very likely that [corporal punishment] is much more common than was reported in our study.''
The idea that watching TV makes children more aggressive is controversial. Waikato University media studies professor Geoff Lealand, who has just co-authored a study of media use by 860 children aged between 8 and 13, said he was sceptical about the claim.
‘‘There is a naivety to it, in that parents will be distracted from their serious family problems and blame TV,'' he said.
‘‘The two primary sources of violence in society are two things we are unwilling to do anything about - private car ownership, which causes more violence than anything else, and alcohol.''
His study found an even split between families which laid down rules about their children's TV watching and those who did not, and it found that 47% of children had personal access to a TV set - often in their own bedrooms.
In Dr Barkin's US study, only 36% of children had TV sets in their bedrooms and only 7% of parents said they did not impose any limits on their children's viewing.
A quarter of the parents (23%) restricted what and when their children could watch, 11% discussed things their children saw on TV, and 59% used a mixture of restrictions, discussion and simply watching TV with their children.
Dr Barkin said children's brains developed by ‘‘serve and return'', as in a tennis match, where their experiences built up brain connections, and that inbuilt ‘‘wiring'' then encouraged them to respond to new experiences in the same ways.
‘‘We know that young children exposed to maltreatment, including abuse and neglect, have smaller brain sizes. They build less brain material.''
She said the blue range of the light from TV and computer screens affected a child's hormones. If you look at what's going on in your brain [when watching TV], your brain waves move into stage one hypnosis,'' she said.
‘‘The ad agencies know that. That's why most primetime TV shows have about 12 minutes of ads. You are in stage one hypnosis so the likelihood that you will actually buy those things goes up.''
She cited other studies showing that TV exposure was associated with aggression, desensitisation, poor mora reasoning, obesity and a lower attention span.
However, other studies found TV associated with more positive socia interactions, higher intelligence and better school performance.
‘‘The difference exists in the content of the programming and the time spent engaged in media use,'' she said.
On this basis, the American Academy of Paediatrics recommends no TV for infants under 2 and one to two hours a day of educational, quality programmes for older children.
Another local expert, Dr Geoff Bridgman at Unitec, said there was only weak evidence that watching violent TV programmes made children violent, but there was powerful evidence that too much TV reduced the time for other experiences that helped to develop children's brains, such as socialising, sports and arts.
A clinical adviser for the Plunket Society, Erin Beatson, said Plunket nurses told mothers from their first visits with a newborn baby about the importance of stimulating their children's brain development.
‘‘We talk a lot about conscious parenting - what type of parent do you want to be, what happened in your childhood and what would you like to happen in your child's life,'' she said.
‘‘We would always promote a range of activities including physical activities watching TV, reading books, puzzles whatever is appropriate to the developmental age. - The New Zealand Herald