BigThink has an interesting post entitled "From Papyrus to iPad: The Evolution of Reading" by technology writer Nicholas Carr. The post consists of a video as well as the transcript of his talk. He notes that spaces between words were only invented around 800 or 900 AD, before which reading was a more cognitively intensive act. The advent of eReaders threatens to revive this complexity. He says that reading is again "becomes a more cognitively intensive act, the way it was back when there were no spaces between words. And as a result, I think we begin to lose the ability to read in the deepest, most interpretive ways because were not kind of calming our mind and just focusing on the argument or the story."