CHICAGO — One-fifth of infants and toddlers under age 2 have a television in their bedrooms, according to a new study that suggests saturation with media could affect brain development as more shows start to target America's youngest children.

Previous studies have found that bedroom TVs are linked with childhood obesity, inactivity and low scores on reading and math tests. Research also suggests that extensive viewing before age 3 may cause attention problems later on.

The children's viewing practices reflected their parents' often guilty reliance on TV, said authors of the study, to be published today in the journal Pediatrics. Asked why they put TVs in their children's bedrooms, most parents said it was so they and other family members could watch their own shows.