To quote from that page: "Kana are read phonetically and kanji are read visually, with a dissociation between the processes involved, according to Morton & Sasanuma and popular Japanese belief. (This must be a little awkward in reading pages of mixed text, surely?) Nomura found that meaning was extracted faster from kanji than kana words, and thought that kana pronunciation was data-driven and that kanji pronunciation was conceptually-driven. Morton & Sasanuma (1982) also claimed that evidence supports the intuitive belief that kanji can give direct access to the meaning of words, but that kana always require translation into a phonological code when they are being read, and there is no development of automatic visual recognition of the kana symbols."
I believe Japanese uses the ideographic kanji for nouns, plus some adjectival and verbal roots, and the phonological kana for the rest, e.g. grammar words. In English, these same words classes (nouns, adjectives, inluding adverbs ending in -ly, and mosts verbs, except the most common ones) are the words we stress when speaking. Is this the same principle at work in both Japanese and English, where the content words of a language are stressed and easier to remember semantically, and the grammar words and morphological inflections are unstressed and easier to remember phonologically?
Is this also why in written German, the nouns are capitalized (as was Dutch until 50yrs ago and English until a few hundred years ago), because it helps if they stand out?
Have you heard about the ideographic myth?