[gigamonkey]

You should check out the book The Myth of the Paperless Office. They report research where they gave folks tasks like writing a summary of several magazine articles and one group did it all on a computer and the other did it on paper and they watched how people actually worked. There was a lot of subtle physical interactions in the paper group, such as moving different articles closer and farther away on the table that the computer group tried to do analogues of and failed because of the limitations of the medium. So it's not just the eyes and ears.

[Gormo]

The position of the paper on the table seems like an entirely visual variable. What information about the documents or the content within them did the latter group ascertain through tactile senses?

I'd assume that the amount of information about the content that was acquired tactilely was none. Feeling the paper can only give you information about the paper medium itself, not the ideas encoded in written language on it - conceptual content is non-tangible, by definition.

So the mistake the computer group made was to try to model the human-paper interaction with software, when software isn't made out of paper. They should have attempted to figure out what human-content interaction was being proxied via re-positioning the paper, and modeled that in the software.