Why isn't that also the case in heavy book readers? It is a solitary sport in which hours upon hours are spent in blocking out the world around you. Two people sitting next to each other reading may as well be in different worlds.
[WS:] I think there are qualitatively fundamental differences between any video-based information and print. One of them is who controls the pace at which the information is dispensed and absorbed. The second one is the organization of the content. The other one is the efficiency in expressing and transmitting abstract ideas.
In case of book reading - it is the reader who decides the pace of the reading, where to pause, and reflect on the contents, go back, concentrate on individual sentence or phrases, etc. (unless, of course one does the so called speed "reading" an abomination that could only be invented in philistine America). In case of video- media, that pace is controlled by the programmer and the audience is, for the most part captive of that pace. Modern technology, such as VCR or DVD gives the recipient some capacity to control the pace (i.e. by stopping and rewinding) but this capacity is quite limited vis a vis that of a printed document.
Second, printed information can easily be organized into logical chunks, such as sentences, paragraphs, pages, or chapters. This stimulates the reader to look for an overall coherence, a structure, a big picture. Video, by contrast, is a continuous stream of visual stimuli that cannot be as easily organized into smaller logical chunks. It is possible, but not as efficiently as in case of print.
Third, print by nature is better suited to express abstract ideas, whereas video-based narrative is naturally centered on visual details. Again, it is possible to express abstract ideas in a video-format, but it is not as easy and efficient as it is in print.
As a result, processing of printed information requires a much greater cognitive and intellectual involvement and effort of the recipient in processing and reconstructing the information, whereas video-based lends it itself to passive receptivity. I think there is some truth in the observation that smart people would rather read a book, whereas dimwits would rather watch a mooovie (which is not as taxing on their intellectual capabilities as reading).
This of course, does not mean that receiving video-based information is naturally dumb. It certainly is not if it is done in conjunction with - or perhaps as supplement to - receiving print-based information. These two actually complement one another: one is better at conveying abstract ideas, the other one - perceptual detail. However, if video-based information REPLACES the print based-information, it inevitably leads to intellectual passivity, avoidance of abstract ideas, and general dumbing down of the audience.
Wojtek