readability for code readability see computer programming readability of source code readability is the ease with which a reader can understand a written text in natural language the readability of text depends on its content the complexity of its vocabulary and syntax and its presentation such as typographic aspects like font size line height and line length researchers have used various factors to measure readability such as speed of perception perceptibility at a distance perceptibility in peripheral vision visibility reflex blink technique rate of work reading speed eye movements fatigue in reading readability is more than simply legibilitywhich is a measure of how easily a reader can distinguish individual letters or characters from each other higher readability eases reading effort and speed for any reader but it is especially important for those who do not have high reading comprehension in readers with average or poor reading comprehension raising the readability level of a text from mediocre to good can make the difference between success and failure of its communication goals readability exists in both natural language and programming languages though in different forms in programming things such as programmer comments choice of loop structure and choice of names can determine the ease with which humans can read computer program code definition people have defined readability in various ways eg in the literacy dictionary easy reading helps learning and enjoyment so what we write should be easy to understand while many writers and speakers since ancient times have used plain language by the year 2000 there were over 1000 studies on readability formulas in professional journals about their validity and merit there are summaries of this research see the links in this section many textbooks on reading include pointers to readability early research in the 1880s english professor l a sherman found that the english sentence was getting shorter in elizabethan times the average sentence was 50 words long in his own time it was 23 words long shermans work established that literature is a subject for statistical analysis shorter sentences and concrete terms help people to make sense of what is written speech is easier to understand than text over time text becomes easier if it is more like speech sherman wrote literary english in short will follow the forms of standard spoken english from which it comes no man should talk worse than he writes no man should write better than he should talk the oral sentence is clearest because it is the product of millions of daily efforts to be clear and strong it represents the work of the race for thousands of years in perfecting an effective instrument of communication in 1889 in russia the writer nikolai a rubakin published a study of over 10000 texts written by everyday people in 1921 harry d kitson published the mind of the buyer one of the first books to apply psychology to marketing kitsons work showed that each type of reader bought and read their own type of text on reading two newspapers and two magazines he found that short sentence length and short word length were the best contributors to reading ease text leveling the earliest reading ease assessment is the subjective judgment termed text leveling formulas do not fully address the various content purpose design visual input and organization of a text text leveling is commonly used to rank the reading ease of texts in areas where reading difficulties are easy to identify such as books for young children at higher levels ranking reading ease becomes more difficult as individual difficulties become harder to identify this has led to better ways to assess reading ease vocabulary frequency lists in the 1920s the scientific movement in education looked for tests to measure students achievement to aid in curriculum development teachers and educators had long known that to improve reading skill readersespecially beginning readersneed reading material that closely matches their ability universitybased psychologists did much of the early research which was later taken up by textbook publishers educational psychologist edward thorndike of columbia university noted that in russia and germany teachers used word frequency counts to match books to students word skill was the best sign of intellectual development and the strongest predictor of reading ease in 1921 thorndike published teachers word book which contained the frequencies of 10000 words it made it easier for teachers to choose books that matched class reading skills it also provided a basis for future research on reading ease until computers came along word frequency lists were the best aids for grading reading ease of texts early childrens readability formulas in 1923 bertha a lively and sidney l pressey published the first reading ease formula they were concerned that junior high school science textbooks had so many technical words they felt that teachers spent all class time explaining these words they argued that their formula would help to measure and reduce the vocabulary burden of textbooks their formula used five variable inputs and six constants for each thousand words it counted the number of unique words the number of words not on the thorndike list and the median index number of the words found on the list manually it took three hours to apply the formula to a book after the livelypressey study people looked for formulas that were more accurate and easier to apply by 1980 over 200 formulas were published in different languages between 1929 and 1939 alfred lewerenz of the los angeles school district published several new formulas in 1934 edward thorndike published his formula he wrote that word skills can be increased if the teacher introduces new words and repeats them often early adult readability formulas during the recession of the 1930s the us government invested in adult education in 1931 douglas waples and ralph tyler published what adults want to read about it was a twoyear study of adult reading interests their book showed not only what people read but what they would like to read they found that many readers lacked suitable reading materials they would have liked to learn but the reading materials were too hard for them lyman bryson of teachers college columbia university found that many adults had poor reading ability due to poor education even though colleges had long tried to teach how to write in a clear and readable style bryson found that it was rare he wrote that such language is the result of a discipline and artistry that few people who have ideas will take the trouble to achieve if simple language were easy many of our problems would have been solved long ago bryson helped set up the readability laboratory at the college two of his students were irving lorge and rudolf flesch in 1934 ralph ojemann investigated adult reading skills factors that most directly affect reading ease and causes of each level of difficulty he did not invent a formula but a method for assessing the difficulty of materials for parent education he was the first to assess the validity of this method by using 16 magazine passages tested on actual readers he evaluated 14 measurable and three reported factors that affect reading ease ojemann emphasized the reported features such as whether the text was coherent or unduly abstract he used his 16 passages to compare and judge the reading ease of other texts a method now called scaling he showed that even though these factors cannot be measured they cannot be ignored also in 1934 ralph tyler and edgar dale published the first adult reading ease formula based on passages on health topics from a variety of textbooks and magazines of 29 factors that are significant for young readers they found ten that are significant for adults they used three of these in their formula in 1935 william s gray of the university of chicago and bernice leary of xavier college in chicago published what makes a book readable one of the most important books in readability research like dale and tyler they focused on what makes books readable for adults of limited reading ability their book included the first scientific study of the reading skills of american adults the sample included 1690 adults from a variety of settings and regions the test used a number of passages from newspapers magazines and booksas well as a standard reading test they found a mean grade score of 781 eighth month of the seventh grade about onethird read at the 2nd to 6thgrade level onethird at the 7th to 12thgrade level and onethird at the 13th17th grade level the authors emphasized that onehalf of the adult population at that time lacked suitable reading materials they wrote for them the enriching values of reading are denied unless materials reflecting adult interests are adapted to their needs the poorest readers onesixth of the adult population need simpler materials for use in promoting functioning literacy and in establishing fundamental reading habits gray and leary then analyzed 228 variables that affect reading ease and divided them into four types content style format organization they found that content was most important followed closely by style third was format followed closely by organization they found no way to measure content format or organizationbut they could measure variables of style among the 17 significant measurable style variables they selected five to create a formula average sentence length number of different hard words number of personal pronouns percentage of unique words number of prepositional phrases their formula had a correlation of 645 with comprehension as measured by reading tests given to about 800 adults in 1939 irving lorge published an article that reported other combinations of variables that indicate difficulty more accurately than the ones gray and leary used his research also showed that the vocabulary load is the most important concomitant of difficulty by 1940 investigators had successfully used statistical methods to analyze reading ease found that unusual words and sentence length were among the first causes of reading difficulty used vocabulary and sentence length in formulas to predict reading ease popular readability formulas the flesch formulas fleschkincaid readability tests in 1943 rudolf flesch published his phd dissertation marks of a readable style which included a readability formula to predict the difficulty of adult reading material investigators in many fields began using it to improve communications one of the variables it used was personal references such as names and personal pronouns another variable was affixes in 1948 flesch published his reading ease formula in two parts rather than using grade levels it used a scale from 0 to 100 with 0 equivalent to the 12th grade and 100 equivalent to the 4th grade it dropped the use of affixes the second part of the formula predicts human interest by using personal references and the number of personal sentences the new formula correlated 070 with the mccallcrabbs reading tests the original formula is reading ease score 206835 1015 asl 846 asw where asl average sentence length number of words divided by number of sentences asw average word length in syllables number of syllables divided by number of words publishers discovered that the flesch formulas could increase readership up to 60 percent fleschs work also made an enormous impact on journalism the flesch reading ease formula became one of the most widely used and the one most tested and reliable in 1951 farr jenkins and patterson simplified the formula further by changing the syllable count the modified formula is new reading ease score 1599nosw 1015sl 31517 where nosw number of onesyllable words per 100 words and sl average sentence length in words in 1975 in a project sponsored by the us navy the reading ease formula was recalculated to give a gradelevel score the new formula is now called the fleschkincaid gradelevel formula the dalechall formula dalechall readability formula edgar dale a professor of education at ohio state university was one of the first critics of thorndikes vocabularyfrequency lists he claimed that they did not distinguish between the different meanings that many words have he created two new lists of his own one his short list of 769 easy words was used by irving lorge in his formula the other was his long list of 3000 easy words which were understood by 80 of fourthgrade students in 1948 he incorporated this list into a formula he developed with jeanne s chall who later founded the harvard reading laboratory to apply the formula select several 100word samples throughout the text compute the average sentence length in words divide the number of words by the number of sentences compute the percentage of words not on the dalechall word list of 3000 easy words compute this equation raw score 01579pdw 00496asl 36365 where raw score uncorrected reading grade of a student who can answer onehalf of the test questions on a passage pdw percentage of difficult words not on the dalechall word list asl average sentence length finally to compensate for the gradeequivalent curve apply the following chart for the final score raw score final score49 and below grade 4 and below5059 grades 566069 grades 787079 grades 9108089 grades 11129099 grades 1315 college10 and above grades 16 and above correlating 093 with comprehension as measured by reading tests the dalechall formula is the most reliable formula and is widely used in scientific research in 1995 dale and chall published a new version of their formula with an upgraded word list the new dalechall readability formula the gunning fog formula gunning fog index in the 1940s robert gunning helped bring readability research into the workplace in 1944 he founded the first readability consulting firm dedicated to reducing the fog in newspapers and business writing in 1952 he published the technique of clear writing with his own fog index a formula that correlates 091 with comprehension as measured by reading tests the formula is one of the most reliable and simplest to apply grade level 04 average sentence length percentage of hard words where hard words words with more than two syllables fry readability graph fry readability formula in 1963 while teaching english teachers in uganda edward fry developed his readability graph it became one of the most popular formulas and easiest to apply mclaughlins smog formula smog harry mclaughlin determined that word length and sentence length should be multiplied rather than added as in other formulas in 1969 he published his smog simple measure of gobbledygook formula smog grading 3 polysyllable count where polysyllable count number of words of more than two syllables in a sample of 30 sentences the smog formula correlates 088 with comprehension as measured by reading tests the forcast formula in 1973 a study commissioned by the us military of the reading skills required for different military jobs produced the forcast formula unlike most other formulas it uses only a vocabulary element making it useful for texts without complete sentences the formula satisfied requirements that it would be based on armyjob reading materials suitable for the young adultmale recruits easy enough for army clerical personnel to use without special training or equipment the formula is grade level 20 n 10 where n number of singlesyllable words in a 150word sample the forcast formula correlates 066 with comprehension as measured by reading tests readability and newspaper readership several studies in the 1940s showed that even small increases in readability greatly increases readership in largecirculation newspapers in 1947 donald murphy of wallaces farmer used a splitrun edition to study the effects of making text easier to read they found that reducing from the 9th to the 6thgrade level increased readership 43 for an article on nylon there was a gain of 42000 readers in a circulation of 275000 he found a 60 increase in readership for an article on corn he also found a better response from people under 35 wilber schramm interviewed 1050 newspaper readers he found that an easier reading style helps to decide how much of an article is read this was called reading persistence depth or perseverance he also found that people will read less of long articles than of short ones a story 9 paragraphs long will lose three out of 10 readers by the 5th paragraph a shorter story will lose only two schramm also found that the use of subheads boldface paragraphs and stars to break up a story actually lose readers a study in 1947 by melvin lostutter showed that newspapers generally were written at a level five years above the ability of average american adult readers he also found that the reading ease of newspaper articles had little to do with the education experience or personal interest of the journalists writing the stories it had more to do with the convention and culture of the industry lostutter argued for more readability testing in newspaper writing he wrote that improved readability must be a conscious process somewhat independent of the education and experience of the staffs writers a study by charles swanson in 1948 showed that better readability increases the total number of paragraphs read by 93 and the number of readers reading every paragraph by 82 in 1948 bernard feld did a study of every item and ad in the birmingham news of 20 november 1947 he divided the items into those above the 8thgrade level and those at the 8th grade or below he chose the 8thgrade breakpoint because that was the average reading level of adult readers an 8thgrade text will reach about 50 percent of all american grownups he wrote among the wireservice stories the lower group got twothirds more readers and among local stories 75 percent more readers feld also believed in drilling writers in fleschs clearwriting principles both rudolf flesch and robert gunning worked extensively with newspapers and the wire services in improving readability mainly through their efforts in a few years the readability of us newspapers went from the 16th to the 11thgrade level where it remains today the two publications with the largest circulations tv guide 13 million and readers digest 12 million are written at the 9thgrade level the george klare studies george klare and his colleagues looked at the effects of greater reading ease on air force recruits they found that more readable texts resulted in greater and more complete learning they also increased the amount read in a given time and made for easier acceptance other studies by klare showed how the readers skills affect reading ease measuring coherence and organization for centuries teachers and educators have seen the importance of organization coherence and emphasis in good writing beginning in the 1970s cognitive theorists began teaching that reading is really an act of thinking and organization the reader constructs meaning by mixing new knowledge into existing knowledge because of the limits of the reading ease formulas some research looked at ways to measure the content organization and coherence of text although this did not improve the reliability of the formulas their efforts showed the importance of these variables in reading ease studies by walter kintch and others showed the central role of coherence in reading ease mainly for people learning to read bonnie meyer and others tried to use organization as a measure of reading ease while this did not result in a formula they showed that people read faster and retain more when the text is organized in topics she found that a visible plan for presenting content greatly helps readers to assess a text a hierarchical plan shows how the parts of the text are related it also aids the reader in blending new information into existing knowledge structures bonnie armbruster found that the most important feature for learning and comprehension is textual coherence which comes in two types global coherence which integrates highlevel ideas as themes in an entire section chapter or book local coherence which joins ideas within and between sentences armbruster confirmed kintschs finding that coherence and structure are more help for younger readers many other studies looked at the effects on reading ease of other text variables including image words abstraction direct and indirect statements types of narration and sentences phrases and clauses difficult concepts idea density human interest nominalization active and passive voice embeddedness structural cues the use of images diagrams and line graphs highlighting fonts and layout document age advanced readability formulas the john bormuth formulas john bormuth of the university of chicago looked at reading ease using the new cloze deletion test developed by wilson taylor his work supported earlier research including the degree of reading ease for each kind of reading the best level for classroom assisted reading is a slightly difficult text that causes a set to learn and for which readers can correctly answer 50 percent of the questions of a multiplechoice test the best level for unassisted reading is one for which readers can correctly answer 80 percent of the questions these cutoff scores were later confirmed by vygotsky among other things bormuth confirmed that vocabulary and sentence length are the best indicators of reading ease he showed that the measures of reading ease worked as well for adults as for children the same things that children find hard are the same for adults of the same reading levels he also developed several new measures of cutoff scores one of the most well known was the mean cloze formula which was used in 1981 to produce the degree of reading power system used by the college entrance examination board the lexile framework in 1988 jack stenner and his associates at metametrics inc published a new system the lexile framework for assessing readability and matching students with appropriate texts the lexile framework uses average sentence length and average word frequency in the american heritage intermediate corpus to predict a score on a 02000 scale the ahi corpus includes five million words from 1045 published works often read by students in grades three to nine the lexile book database has more than 100000 titles from more than 450 publishers by knowing a students lexile score a teacher can find books that match his or her reading level atos readability formula for books in 2000 researchers of the school renaissance institute and touchstone applied science associates published their advantagetasa open standard atos reading ease formula for books they worked on a formula that was easy to use and that could be used with any texts the project was one of the widest reading ease projects ever the developers of the formula used 650 normed reading texts 474 million words from all the text in 28000 books read by students the project also used the reading records of more than 30000 who read and were tested on 950000 books they found that three variables give the most reliable measure of text reading ease words per sentence average grade level of words characters per word they also found that to help learning the teacher should match book reading ease with reading skill reading often helps with reading gains for reading alone below the 4th grade the best learning gain requires at least 85 comprehension advanced readers need 92 comprehension for independent reading book length can be a good measure of reading ease feedback and interaction with the teacher are the most important factors in reading cohmetrix psycholinguistics measurements cohmetrix can be used in many different ways to investigate the cohesion of the explicit text and the coherence of the mental representation of the text our definition of cohesion consists of characteristics of the explicit text that play some role in helping the reader mentally connect ideas in the text using the readability formulas while experts agree that the formulas are highly accurate for grading the readability of existing texts they are not so useful for creating or modifying them the two variables used in most formulas a sentence and a vocabulary are the ones most directly related to reading difficulty but they are not the only ones writing experts have warned that an attempt to simplify the text only by changing the length of the words and sentences may result in text that is more difficult to read all the variables are tightly related if one is changed the others must also be adjusted including approach voice person tone typography design and organization writing for a class of readers other than ones own is very difficult it takes training method and practice among those who are good at this are writers of novels and childrens books the writing experts all advise that besides using a formula observe all the norms of good writing which are essential for writing readable texts writers should study the texts used by their audience and their reading habits this means that for a 5thgrade audience the writer should study and learn good quality 5thgrade materials wikiversity has learning resources about wikiversityreadability look up readability in wiktionary the free dictionary asemic writing plain language verbosity accessible publishing list of plain english words and phrases george r klare william s gray miles tinker bourbaki dangerous bend symbol vtereadability tests for englishtests and formulas that measure the readability of a text automated readability index 1967 atos colemanliau index 1975 dalechall readability formula 1948 fleschkincaid readability tests flesch reading ease fleschkincaid grade level forcast 1973 fry readability formula 1968 gunning fog index 1952 lexile 1989 linsear write raygor readability estimate 1977 smog 1969 spache readability formula 1952 