Even the most educational programming in terms of content is delivered via a medium that affects the brain adversely. A highly informative show on the history of Henry VIII, for example, might have frequent "cuts" where the camera changes angles. This conditions the brain to nearly constant visual stimulation unlike reading, which relies on constant mental stimulation to make the reader produce the images in their own head. So you could learn something about Henry VIII, but your brain would be conditioned just a little bit for the worse, making your faculties less sharp than the scholars whose work originally provided the material for the program. Of course a single hour doesn't do grave harm, especially not if you're motivated to turn off the tv and read more about Henry VIII in this case. But when I fall into the lazy habit of vegging out to the History Channel all Sunday afternoon, I'm not doing my brain much good, although perhaps it has value merely as a relaxation technique.
