Therein lies one of the biggest problems with traditional RSVP. Each time you see text that is not centered properly on the ORP position, your eyes naturally will look for the ORP to process the word and understand its meaning. This requisite eye movement creates a “saccade”, a physical eye movement caused by your eyes taking a split second to find the proper ORP for a word. Every saccade has a penalty in both time and comprehension, especially when you start to speed up reading. Some saccades are considered by your brain to be “normal” during reading, such as when you move your eye from left to right to go from one ORP position to the next ORP position while reading a book. Other saccades are not normal to your brain during reading, such as when you move your eyes right to left to spot an ORP. This eye movement is akin to trying to read a line of text backwards. In normal reading, you normally won’t saccade right-to-left unless you encounter a word that your brain doesn’t already know and you go back for another look; those saccades will increase based on the difficulty of the text being read and the percentage of words within it that you already know.
And the math doesn’t look good, either. If you determined the length of all the words in a given paragraph, you would see that, depending on the language you’re reading, there is a low (less than 15%) probability of two adjacent words being the same length and not requiring a saccade when they are shown to you one at a time. This means you move your eyes on a regular basis with traditional RSVP! In fact, you still move them with almost every word. In general, left-to-right saccades contribute to slower reading due to the increased travel time for the eyeballs, while right-to-left saccades are discombobulating for many people, especially at speed. It’s like reading a lot of text that contains words you don’t understand only you DO understand the words! The experience is frustrating to say the least.