It is already known that parent input is important in developing children's language skills, and that a reduction in child-directed language could have a negative impact on their language development, researchers said.
The new study suggests that the presence of background TV is a significant factor in reducing this vital input, affecting both the quantity and quality of language spoken by parents to their children.
In the study, parents of toddlers aged 12, 24, and 36 months were observed interacting with their children while they played during a 60 minute session, with a TV programme on in the background for half of that time.
Background TV is defined as content designed for older children or adults. While the TV was on, the quantity of words and phrases as well as the number of new words spoken by the parents was lower than when the TV was off. However, the length of the phrases spoken was not affected.
Given that the language used by parents is so intrinsically linked with child language development, the results of the study suggest that prolonged exposure to background TV has a negative influence, researchers said.
"Our new results, along with past research finding negative effects of background TV on young children's play and parent-child interaction, provide evidence that adult-directed TV content should be avoided for infants and toddlers whenever possible," said Tiffany A Pempek, author of the study published in the Journal of Children and Media.