Recordings that claim to stimulate baby brain development may actually slow vocabulary development in infants if they are overused, US researchers reported on Wednesday.
For every hour per day spent watching baby DVDs and videos, infants aged 8 to 16 months understood an average of six to eight fewer words than babies who did not watch them, Frederick Zimmerman of the University of Washington and colleagues found.
Older toddlers were not harmed or helped by the videos, the researchers reported in the Journal of Pediatrics.
"The most important fact to come from this study is there is no clear evidence of a benefit coming from baby DVDs and videos, and there is some suggestion of harm," Zimmerman said in a statement.
"The bottom line is the more a child watches baby DVDs and videos, the bigger the effect."
Zimmerman and colleagues conducted telephone interviews with more than 1,000 families in Minnesota and Washington with babies and asked detailed questions about television and video viewing.
Parents of the 8 to 16-month-olds were asked how many words like "choo-choo," "mommy" and "nose" their child understood. Parents of the toddlers were asked how many words like "truck," "cookie" and "balloon" their children knew.
Dr Dimitri Christakis, a pediatrician at Seattle Children's Hospital Research Institute who worked on the study, said: "The evidence is mounting that they (educational videos) are of no value and may in fact be harmful."
Source: China Daily/agencies