My understanding of words is strictly phonological. I do not visualize words in my head well, rather the image that pops up is of the object or sometimes a color I associate with a more abstract word (e.g.: I read or hear "car" and immediately visualize the object, not the letters of the word. For the more abstract word "philosophy," I just see yellow). This method is so ingrained that my efforts to visualize words have not come very far. If a word is not spelled phonetically (I do fine with phonetic words), then much of my memory for how to spell it comes from the muscle memory of typing or writing. If the word is short enough and I make the effort to see the word rather than the object, then I can visualize the word, though this is not my natural inclination.
I believe that my highly phonetics-based understanding of the written word also accounts for my inability to speed read. I have tried speed reading, but it relies on a visual understanding of words. For me, the visual stimulus (written words) must first be translated into a phonological mental representation (in other words, me talking to myself in my head) before I can access the meaning of the word. This process happens in a split second, so I can still read quickly, but only as fast as I can talk (as I am talking to myself in my mind as I read). I will not understand a word if I only glance at it and do not say it to myself. The meaning is only accessed once the phonetic representation is produced. Of course, it is such an automatic response that I usually cannot force myself to glance at word without mentally saying it. I do miss some road signs though, because of this phenomena. A friend will ask as we drive, "well didn't you see that big green sign a few miles back?" and I will recall having seen the sign, but not what was written as I did not bother to translate the material. Good speed readers, on the other hand, can access the meaning of words visually. The need for translation into a phonetic mental representation does not exist, so the speed of reading is only hindered by the speed of vision and understanding.
This whole talking in my head business has its benefits. For one, e-mails, letters, and books seem more conversational. Each writer gets their own voices as they speak to me in my mind. Plus, this makes me a better writer as everything I write is being said in my head at the same time. The writing then comes out very smoothly, as if I were just talking (because that is essentially what I am doing in my mind as I type).
I wonder how many other people approach reading in this fashion and which is more common.