How to reach readers in the face of global illiteracy
How can you write for adults who can barely read? That’s what two Chicago academics — William S. Gray and Bernice Leary — set out to learn in 1935.
To discover what makes prose readable for adults with low literacy rates, the University of Chicago’s Gray and St. Xavier College’s Leary studied 48 passages of about 100 words each, taken from books, magazines and newspapers most widely read by adults.
To establish the difficulty of these passages, the researchers gave 800 adults a reading comprehension test. These adults read the passages, then answered questions that tested their ability to understand the main idea of the passage.
The results: a landmark book in reading research, What Makes a Book Readable, published in 1935.
Four components of readability
In the book, Gray and Leary first identified 228 elements that affect readability and grouped them under these four headings:
- Content — arguments, structure, coherence
- Style — semantic (words) and syntactic (sentences)
- Design — typography, layout, illustrations
- Organization — chapters, navigation, headings
17 ways to increase readability
Then Gray and Leary listed elements of readability with correlations of 35% or higher in hierarchical order. Here’s how you can use their list to improve readability of your copy:
- Reduce average number of words per sentence. Average sentence length had a -52% correlation in Gray and Leary’s study. This negative correlation means that the longer the sentence, the more difficult it is to read.
How short? To achieve 90% comprehension, aim for sentences of 9 to 14 words, on average.
- Choose easy words. The percentage of easy words had a 52% correlation with ease of reading, Gray and Leary found. That means that the more easy words you use, the easier your message becomes to read.
The words we use most often are the easiest to understand, discovered researcher Edward L. Thorndike of Columbia University in 1921. Find the 86,800 most frequently used words in the English language.
- Seriously, choose easy words. The number of easy words scored a 51% correlation with ease of reading.
- Choose familiar words. The number of words not known to 90% of sixth-grade students had a -51% correlation with ease of reading. That means the fewer of these you use, the better.
- Did we say, “Choose easy words”? The number of different hard words had a -50% correlation with ease of reading. That is, the more different hard words you use, the harder your message is to read.
- Reduce the “minimum syllabic sentence length.” Neither I nor my best friend and research assistant, Google, can tell you what this means. But it had a -49% correlation with reading ease, which means that less is better.
- Write explicit sentences. The number of explicit sentences had a 48% correlation with ease of reading. That means the more explicit sentences, the easier your message is to read.
[Explicit] “Students enjoyed taking the course” is an explicit sentence because it has a precise subject: students.[Inexplicit] “Taking the course was a great idea” is inexplicit, because “Taking the course” is the subject, and we don’t know who did it.
- Use more personal pronouns. The number of personal pronouns had 48% correlation with reading ease. That means the more personal pronouns, the better. So use more:
- First-person pronouns (I, me, us, we)
- Second-person pronouns (you)
- Third-person pronouns (she, her, he, etc.)
Note that this isn’t an invitation to use more pronouns in general. So don’t increase your use of:
- Relative pronouns (that, which, whom, etc.)
- Demonstrative pronouns (this, these, that, etc.)
- Indefinite pronouns (anybody, anyone, anything, etc.)
- Reflexive pronouns (myself, yourself, herself, etc.)
- Interrogative pronouns (what, who, which, etc.)
- Possessive pronouns (mine, yours, his, etc.)
- Subject and object pronouns (me, you, her, etc.)
- Reduce the “maximum syllabic sentence length.” I don’t know what it is, but I’m going to try to do less of it: This had a -47% correlation with reading ease, which means less is better.
- Reduce the number of syllables per sentence. “Average sentence length in syllables” saw a -47% correlation in the Gray and Leary study. That means fewer syllables per sentence is better. And that’s another argument for shorter words and shorter sentences.
- Increase the percentage of one-syllable words. Percentage of monosyllables had a 43% correlation with reading ease in the study. That means the more one-syllable words you use, the better.
- Write short paragraphs. The number of sentences per paragraph had a 43% correlation with reading ease in the Gray and Leary study. How short? Five lines or less on the page, suggests the Medill School of Journalism’s Jon Ziomek.
- Did we say, “Reduce unfamiliar words?” Because we really, really mean it. Percentage of different words not known to 90% of sixth-grade students had a -40% correlation with reading ease.
- Write subject-verb-object. The number of simple sentences had a 39% correlation with reading ease in the study. So structure your sentences for clarity.
- Reduce the number of different words. Percentage of different words had a -38% correlation with ease of reading. That is, the fewer different words, the better.
- Reduce the number of two- or more-syllable words. Percentage of polysyllables had a -38% correlation with reading ease. Which means that fewer are better.
- Reduce the number of prepositional phrases. This measure had a -35% correlation with ease of readership. Which means that the fewer phrases that begin with prepositions like at, by, on and up, the better.
Finally, Gray and Leary developed a readability formula around elements 1, 5, 8, 15 & 17.
Top 2 measures of readability
Notice how many of these top elements of readability boil down to:
- Word length and familiarity (9 measures: Nos. 2, 3, 4, 5, 8, 11, 13, 15 and 16)
- Sentence length and structure (6 measures: Nos. 1, 6, 7, 9, 10 and 14)
That leaves just two measures — paragraph length and prepositional phrases — that don’t address sentences and words. (And you could argue that reducing the number of prepositional phrases will also reduce the sentence length.)
Word length and sentence length continue to be, after all of these years, the top two indicators of ease of reading. So manage your sentence and word length, and you’re far more than halfway down the road to readability.
Source: William H. DuBay, “Unlocking Language: The Classic Readability Studies” (PDF), Impact Information (Costa Mesa), 2006