A row has broken out between entertainment giant Disney and a US university over a study that found videos and DVDs aimed at babies may hinder their language development.
Disney, which makes the "Baby Einstein" videos, demanded that Washington University withdraw a news release that suggested that parents limit their children's exposure to the videos.
The study found that the videos, which are sometimes marketed as tools to aid children's development, slowed vocabulary acquisition in babies aged from eight to 16 months. The scientists found that for every hour spent watching the films, babies understood an average of six to eight fewer words than infants who did not watch them. The videos had no positive or negative effect on the vocabularies of toddlers aged 17 to 24 months. The researchers said more work was needed to see the videos' long-term effects on cognitive development.
The researchers carried out random telephone interviews with more than 1,000 families in Minnesota and Washington with a child born in the previous two years.
They found no positive or negative effects on infants of either age group from viewing educational and non-educational media or adult TV programmes. The baby films differed from other shows because they had little dialogue, short scenes and disconnected pictures, whereas educational films were designed to meet developmental needs, the researchers said.
The team said more work was needed to judge whether the baby films were harmful but added that manufacturers should prove that the films aided cognitive development.
Disney has questioned the methodology of the study, saying that the sample of young babies was small, the study did not control for different rates of child development and it "lumped together" lots of very different baby videos.