Sitting posture: The reader’s posture alone has a measurable influence on his reading speed, because someone who sits upright and with good body tension can concentrate better than someone who lies comfortably on a couch. The lack of body tension alone puts the reader in a state of relaxation, which makes it more difficult to concentrate.
Lighting: Anyone who has to read a text in poor lighting conditions will tire their eyes more quickly simply because of the increased effort required to compensate for the lack of light.
Closely related to the lighting conditions when reading is the contrast that the printing of the text offers the reader, because a gray font on white paper can only be read and understood slowly, while black font on white paper stands out optimally.
The structure and appearance of the text also influence how quickly a page can be read and understood: The line spacing should not be too tight, the text itself should be printed in an easily readable font and set in columns, because with text in columns the individual lines are shorter and also contain fewer words, so that one can grasp the line with a fixation.
It follows that a perfect text, which can be read and understood quickly, is printed in a legible font in black letters on a white paper in columns. The line spacing is at least 1.5 lines. The reader sits in front of this text in an upright posture with good lighting.
The brain is the clock in both speaking and reading
In both speaking and listening, the human brain processes or produces information at a specific rate, where in any language a listener recognizes approximately one unit of information (syllables, words) in 200 milliseconds, i.e., the speech signal is thus characterized by a predominant modulation of the amplitude spectrum between about 4.3 and 5.5 Hz. Interestingly, this time span is also the typical duration of eye fixation when reading letter scripts – only character scripts take longer with about 250 milliseconds. Gagl et al. (2021) have shown that German readers scan written text at ~5 Hz. A meta-analysis of 142 studies from 14 languages confirmed this result and showed that sampling frequencies vary between 3.9 Hz and 5.2 Hz across languages, with this variation systematically depending on the complexity of the writing systems, i.e., whether they are character-based or alphabetic, and on how pronounced orthographic clarity is. Finally, Gagl et al. (2021) empirically demonstrated a positive correlation between the language spectrum and eye movement scanning in low-skilled non-native readers, with a post-hoc analysis providing preliminary evidence for the same relationship in low-skilled native readers. Based on this consistent evidence, the authors suggest that the language processing systems of the human brain have a preferential processing speed during reading, with the speed of spoken language production and perception being transferred to the oculomotor system. Thus, the brain acts as a kind of clock for processing speed during both listening or speaking and reading.