I've heard that television (any program, including those designed for small children (Dora, recent Mickey Mouse, Bubble Guppies) is bad for the development of children, as it damages their ability to learn and retain concepts being taught to them.
They say that children need time to learn things and that television 'overwrites' what they've learned, and damage their imagination.
So, are there studies backing this up? And as a followup, how exactly are programs designed for children damaging?