About 12 per cent of New Zealand preschoolers are getting three or more hours of screen time per day, recent studies have found.
Two recently published studies, using information from the country's largest longitudinal study of child development — Growing Up in New Zealand — looked at how much screen time they are getting and how this might impact their executive functions, such as flexible thinking and working memory.
The University of Auckland's Growing Up in New Zealand study follows more than 6000 children whose mums lived in the Auckland, Counties Manukau and Waikato District Health Board areas during pregnancy.
The children have been followed from birth until they are at least 21.
In their first study, researchers found 66 per cent of children aged two had one hour or less of screen time per day, according to their mothers.
This is in line with Ministry of Health guidelines.
The approximately 12 per cent of two year olds who spent three or more hours per day on screens came down to factors such as a "heavy TV environment" — the TV being on in the same room as them, regardless of whether they were watching it or not — there being no rules on the amount of screen time they could have, and letting them view adult content.
Children who always watched screens with their parents had lower overall levels of screen time, researcher Maria Corkin said.
The second study looked at how screen use at two and four might be related to the development of executive functions and the symptoms of inattention and hyperactivity at 4-and-a-half.
Corkin said executive functions support the development of social skills in preschool years, foster academic competence when children start school, and support success in adult life.
Poorer executive functions at four-and-a-half were associated with the heavy TV environment and eating meals in front of the TV, the study found.
Corkin said watching TV often may mean children are not engaged in other activities.
She said minimising TV and maximising parental involvement in their screen use through co-viewing may help to keep screen time low and potentially help with the development of executive functions.