If you have used a single-word reader, you may have noticed the words are not centred. One letter sits in a fixed spot and the rest of the word arranges itself around it. That spot has a name: the optimal recognition point, usually shortened to ORP.
Readers do not identify a word letter by letter from the left. Word recognition is fastest when the gaze lands slightly left of the middle — for a five-letter word, around the second character. Centre the word instead and your eye has to re-centre on every word, which reintroduces exactly the movement the format exists to remove.
The practical consequence is that alignment matters more than speed. A reader that flashes words at 500 words per minute without aligning them is worse than one at 300 that does, because you are doing micro-saccades on every single word.
The technique itself is old — rapid serial visual presentation goes back to reading research in the 1970s. The specific ORP alignment was popularised by Spritz, whose patent application covers the alignment method. The underlying bucket table — which letter to align for a word of a given length — appears in many open-source implementations, ours included.
Display duration should depend on word length. In a study of readers with central vision loss, varying how long each word stayed on screen by its length improved reading rate by about a third. A fixed duration treats “a” and “extraordinarily” as equal work, which they are not.
The same logic extends to punctuation. A sentence boundary needs a longer gap than a word boundary, or sentences run together — and that costs comprehension for reasons unrelated to speed.
Alignment removes eye movement. It does not raise the ceiling on comprehension. Up to about 350 words per minute understanding holds; past that it drops whether or not the words are aligned. And the study most often cited about Spritz found that comprehension fell while visual fatigue rose — the format is not free.
So ORP is best understood as a correctness requirement rather than a feature. If a reader does it, single-word reading works as intended. If it does not, the format is mostly noise. It is not the thing that makes you faster.
More on the mechanism in what RSVP reading actually does, and on the ceiling in does speed reading hurt comprehension.