I'm not sure about that. Maybe there are some persons that are able to read with extraordinary speed. But does this really imply that speed reading is possible with reasonable training?
In my opinion, one of the main obstacles is the visual perception system. Please take a look at the anatomy of the eye, especially the retina.
According to Wikipedia, the entire retina contains about 7 million cones and 75 to 150 million rods. But there are only around one million ganglion cells that transfer informations to the brain, so there are cells in between that do some kind of processing and compression. Usually the resulting resolution in the peripheral vision field is too low to recognize words. Please take a look at this picture on Wikipedia:
You can try it yourself. Look at a word near the center of a paragraph and try to recognize words at the edge of the paragraph without glimpsing.
A fixation needs some time, which further decreases the limit for reading speed.
Is it possible to train the retina to recognize text in a bigger area with one fixation? I have no idea. Let's assume it isn't, but there are people with a special retina. Maybe they have more ganglion cells than usual so they can indeed read text in the peripheral vision field. Or their ganglion cells are more evenly distributed instead concentrated at the fovea. This would lead to the situation that only few people with a special anatomy are able to learn highspeed reading.
Please correct me if I got something wrong. I'm not a physician.
That issue is one that is not a limiting factor yet. You can make out a lot more words in a line and you can read them within your peripheral vision but you can't exactly recall them as easily, you could port your eyes between every 3 words or so if that was the critical issue.
If you try to visualize the words in your mind, you have difficulty seeing them all at once and reading the words even if you make them up, so I would say there is more to it then that. e.g if you visualize a pile of oranges you can't count them easily in packs of 14 even in your mind, but you don't really have a visual perception issue.
It certainly is one of the main obstacles but it is sort of an unknown factor till the others are solved.
It would be interesting if we were to run tests of different training methods to overcome any limitation, there are certainly things that can be done that haven't been done before , who knows maybe actual speed reading will come into existence.
If all else fails the subvocalization speed should just be increased. For me it is still a wonder why I can listen to songs which say the words 5x faster than I can possible subvocalize them and yet I can recall the song off the top of my head. In my opinion there are many many ways to the same end yet at the same time for now there isn't a satisfactory speed reading method out there.
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