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About Readability

The term 'readability' is used primarily within the scope of research on reading and writing proficiencies. It refers to the ease with which text is understood by readers. Readability formulas have been in use since the 1930s to measure text difficulty in quantitative terms. Readability scores give information on how many years of education are required to read a given text.

Readability formulas

In English, two well-known formulas for measuring readability are the Flesch Reading Ease (FRE) formula [1] and the Flesch-Kincaid Grade Level (FK) formula [2].

  • The FRE is an index of 0-100 that maps to a range of reading difficulty. In general, higher scores mean that more people will be able to read the text.
  • The FK, a later modification of the FRE, directly derives grade level scores. The FK is commonly used as a tool for educators, and is widely documented in academic research, e.g. studies on public accessibility of health information.

The FRE has also been adapted into different languages, such as Dutch, Spanish, and French (cf. [3-5] respectively), but it is not the only type of formula available for measuring readability. Other formulas, e.g. Forcast for English [6], Readability Formula for Japanese [7, 8], and LIX for a variety of European languages [9, 10], assess readability using different variables from those used by the FRE.

Factors assessed

Many factors can potentially affect readability, including writing style, font size, or the layout of text [11-13]. Most readability formulas only account for a few of the factors, specifically sentence- and/or word-length, because these factors are most indicative of reading ease [1, 14]. However, the formulas differ in how they identify measures of sentence- and/or word-length. For example, FRE uses average number of syllables per word as an indicator of word length. Forcast only focuses on the count of one-syllable words and LIX focuses on words with six or more letters.

Readability and web content

With increased availability of information on the Web, the need to assess readability of Web content becomes more important. Given that Web content is continually changing in terms of linguistic and presentation styles, the original factors considered in the development of the formulas may not be sufficient for assessing Web content readability. Pending further research, other factors may need to be used for the measurement of readability of Web content.

The concept of readability also is becoming an important aspect to consider in Web accessibility for individuals with disabilities. The Web Content Accessibility Guidelines 2.0 (WCAG 2.0, draft version) provides a minimum requirement for making Web content understandable and accessible. The guidelines also recommend possible ways of improving readability.

References

  1. Flesch, R., A new readability yardstick. Journal of Applied Psychology, 1948. 32: p. 221-233.
  2. Kincaid, J.P., et al., Derivation of new readability formulas (Automated Readability Index, Fog Count and Flesch Reading Ease Formula) for Navy enlisted personnel. CNTECHTRA Research Branch Report, 1975: p. 8-75.
  3. Douma, W.H., De Leesbaarheid van Landbowbladen: een Onderzoek naar en een Toepassing van Leesbaarheidsformules. Sociologie en Sociographie. Vol. Bulletin No. 17. 1960, Netherlands: Landbouwhogeschool te Wageningen.
  4. Fernández Huerta, J., Medidas sencillas de lecturabilidad. Consigna, 1959. 214: p. 29-32.
  5. Kandel, L. and A. Moles, Application de l'Indice de Flesch à la langue français. Cahiers d'Etudes de Radio-Television, 1958. 19: p. 253-274.
  6. Caylor, J.S., et al., Methodologies for determining reading requirements of military occupational specialties. Technical Report No. 3, 1973: p. 73-75.
  7. Hayashi, Y., A three-level revision model for improving Japanese bad-styled expressions. Proceedings of the 14th Conference on Computational Linguistics, 1992. 2: p. 665-671.
  8. Tateisi, Y., Y. Ono, and H. Yamada, A computer readability formula of Japanese texts for machine scoring. Proceedings of the 12th Conference on Computational Linguistics, 1988. 2: p. 649-654.
  9. Bjornsson, C.H., Läsbarhet. 1968a, Stockholm, Sweden: Bokforlaget Liber.
  10. Bjornsson, C.H., Readability of newspapers in 11 languages. Reading Research Quarterly, 1983. 18: p. 480-497.
  11. Muckenhaupt, M., Text und Bild, in Grundfragen der Beschreibung von Text-BildKommunikation aus sprachwissenschaftlicher Sicht. 1986, Narr: Tübingen.
  12. Meutsch, D., Text- und Bildoptimierung, in Textoptimierung, G. Antos and G. Augst, Editors. 1989, Peter Lang: Frankfurt/Main u.a. p. 8-37.
  13. Bamberger, R. and E. Vanecek, Lesen-Verstehen-Lernen-Schreiben. Die Schwierigkeiten von Texten in der deutschen Sprache. 1984, Wien/Frankfurt/M. /Aarau: Jugend und Volk / Diesterweg / Sauerländer.
  14. Zakaluk, B.L. and S.J. Samuels, Readability: Its past, present, and future. 1988, Newark: International Reading Association.