While the word shape meme is a myth [1] there are some half truths to it.
It is known that mixed casing does disrupt reading [2], which gives some weight to the idea that the shapes of words and letters does affect reading.
For myself I know that my reading speed and comprehension suffers when reading title cased sentences. This leads me to always "fix" [3] documents I update or otherwise contribute to at work when others do it for headings, subheadings, headers and footers.
> In this paper, Pelli and colleagues show that when reading words that have been distorted by presenting each letter in visual noise (like an out of tune television), readers do not perform as well as an 'ideal observer' who can recognise words based on their shape alone
I said being able to see the word shape is very helpful. I did not say that you can read based on the word shape alone.
> The weakest evidence in support of word shape is that lowercase text is read faster than uppercase text. This is entirely a practice effect. Most readers spend the bulk of their time reading lowercase text and are therefore more proficient at it. When readers are forced to read large quantities of uppercase text, their reading speed will eventually increase to the rate of lowercase text.
> Haber & Schindler (1981) found that readers were twice as likely to fail to notice a misspelling in a proofreading task when the misspelling was consistent with word shape (tesf, 13% missed) than when it is inconsistent with word shape (tesc, 7% missed). This is seemingly a convincing result until you realize that word shape and letter shape are confounded. The study compared errors that were consistent both in word and letter shape to errors that are inconsistent both in word and letter shape. Paap, Newsome, & Noel (1984) determined the relative contribution of word shape and letter shape and found that the entire effect is driven by letter shape.
