Visual Illiteracy

Some years ago when I was really into silent movies, there was this discussion on alt.movies.silent of how silent movies never actually had a successor and of how sound film was rather the successor of radioshows. People claimed that when watching a talkie it mostly would suffice to hear the dialogue to keep up with what was going on. No problem to get into the next room and fetch yourself some beverage and snacks if you turned the sound up. On the other hand, if you missed one tiny detail in a silent movie, the rest of the movie could become inexplicable. So you have to stay focused.

There has been a recent survey in Germany suggesting that students are no longer able to keep their attention focused for more than an hour. Thus a lecture that is lasting longer, should have a break. What would be the effect on storytelling either by dialogue or a more cinematic way? I fear that things will become worse, movies, which tend to get longer and longer btw, will go for the cheap sensation, simple conflicts that will get repeated in dialogue at any opportunity and regretfully visual illiteracy will grow even more, since the filmmakers can no longer trust their audience to look and perceive for themselves.