Review of the readability checker DeLite

Continuing a series of reviews on readability assessment, I would like to describe a tool which is close to what I intend to do. It is named DeLite and is named a ‘readability checker’. It has been developed at the IICS research center of the FernUniversität Hagen.

From my point of view, its main feature is that it has not been made publicly available, it is based on software one has to buy and I did not manage to find even a demo version, although they claim to have been publicly (i.e. EU-)funded. Thus, my description is based on what its designers mention in the articles quoted below.


The article by Glöckner et al. (2006) offers a description of the fundamentals of the software, as well as an interesting summary of research on readability. They depict the ‘classical’ pattern used to come to a readability formula :

  • select elements in a text that are related to readability’,
  • then ‘correlate element occurrences with text readability (measured by established comprehension tests)’,
  • and finally ‘combine the variables into a regression equation’ (p. 32).

This is the approach that led to a preponderance of criteria like word and sentence length, because they ...

more ...

On global vs. local visualization of readability

It is not only a matter of scale : the perspective one chooses is crucial when it comes to visualize how difficult a text is. Two main options can be taken into consideration :

  • An overview in form of a summary which enables to compare a series of phenomena for the whole text.
  • A visualization which takes the course of the text into account, as well as the possible evolution of parameters.

I already dealt with the first type of visualization on this blog when I evoked Amazon’s text stats. To sum up, their simplicity is also their main problem, they are easy to read and provide users with a first glimpse of a book, but the kind of information they deliver is not always reliable.

Sooner or later, one has to deal with multidimensional representations as the number of monitored phenomena keeps increasing. That is where a real reflexion on finding a visualization that is faithful and clear at the same time. I would like to introduce two examples of recent research that I find to be relevant to this issue.

An approach inspired by computer science

The first one is taken from an article by Oelke et al. (2010 ...

more ...

Gerolinguistics” and text comprehension

The field of “gerolinguistics” is becoming more and more important. The word was first coined by G. Cohen in 1979 and it has been regularly used ever since.

How do older people read ? How do they perform when trying to understand difficult sentences ? It was the idea I was following when I recently decided to read a few papers about linguistic abilities and aging. As I work on different reader profiles I thought it would be an interesting starting point.

The fact is that I did not find what I was looking for, but was not disappointed since the assumption I had made on this matter were proved wrong by recent research. Here is what I learned.

Interindividual variability increases with age

First of all, it is difficult to build a specific profile that would address ‘older people’, as this is a vast category which is merely a subclass of the ‘readers’, and which (as them) contains lots of variable individual evolutions. Very old people (and not necesarily old people) do have more difficulties to read, but this can be caused by very different factors. Most of all, age is not a useful predictor :

Many aspects of language comprehension remain ...

more ...

Microsoft to analyze social networks to determine comprehension level

I recently read that Microsoft was planning to analyze several social networks in order to know more about users, so that the search engine could deliver more appropriate results. See this article on : Microsoft idea: Analyze social networks posts to deduce mood, interests, education.

Among the variables that are considered, the ‘sophistication and education level’ of the posts is mentionned. This is highly interesting, because it assumes a double readability assessment, on the reader’s side and on the side of the search engine. More precisely, this could refer to a classification task.

Here is an extract of a patent describing how this is supposed to work.

[0117] In addition to skewing the search results to the user’s inferred interests, the user-following engine 112 may further tailor the search results to a user’s comprehension level. For example, an intelligent processing module 156 may be directed to discerning the sophistication and education level of the posts of a user 102. Based on that inference, the customization engine may vary the sophistication level of the customized search result 510. The user-following engine 112 is able to make determinations about comprehension level several ways, including from a user’s ...

more ...

Amazon’s readability statistics by example

I already mentioned Amazon’s text stats in a post where I tried to explain why they were far from being useful in every situation : A note on Amazon’s text readability stats, published last December.

I found an example which shows particularly well why you cannot rely on these statistics when it comes to get a precise picture of a text’s readability. Here are the screenshots of text statistics describing two different books (click on them to display a larger view) :

Comparison of two books on Amazon

The two books look quite similar, except for the length of the second one, which seems to contain significantly more words and sentences.

The first book (on the left) is Pippi Longstocking, by Astrid Lindgren, whereas the second is The Sound and The Fury, by William Faulkner… The writing style could not be more different, however, the text statistics make them appear quite close to each other.

The criteria used by Amazon are too simplistic, even if they usually perform acceptably on all kind of texts. The readability formulas that output the first series of results only take the length of words and sentences into account and their scale is designed for the US school system. In ...

more ...

Interview with children’s books author Sabine Ludwig

Last week I had the chance to talk about complexity and readability with an experienced children’s books author, Sabine Ludwig (see also the page on the German Wikipedia). She has published around 30 books so far, as well as a dozen books which were translated from English to German. Some of them were awarded. The most successful one, Die schrecklichsten Mütter der Welt, had sold about 65.000 copies by the end of 2011 (although a few booksellers first thought it was unadapted to children). I was able to record the interview so that I could take extensive notes afterward, which I am going to summarize.

Sabine Ludwig writes in an intuitive way, which means that she does not pay attention to the complexity of the sentences she creates. She tries to see the world through a child’s eyes, and she pretends that the (inevitable) adaptation of both content and style takes place this way. She does not shorten sentences, neither does she avoid particular words. In fact, she does not want to be perfectly clear and readable for children. She does not find it to be a reasonable goal, because children can progressively learn words from a ...

more ...

Tendencies in research on readability

In a recent article about a readability checker prototype for italian, Felice Dell’Orletta, Simonetta Montemagni, and Giulia Venturi provide a good overview of current research on readability. Starting from the end of the article, I must say the bibliography is quite up-to-date and the authors offer an extensive review of criteria used by other researchers.

Tendencies in research

First of all, there is a growing tendency towards statistical language models. In fact, language models are used by Thomas François (2009) for example, who considers they are a more efficient replacement for the vocabulary lists used in readability formulas.

Secondly, readability assessment at a lexical or syntactic level has been explored, but factors at a higher level still need to be taken into account. It is acknowledged since the 80s that the structure of texts and the development of discourse play a major role in making a text more complex. Still, it is harder to focus on discourse features than on syntactic ones.

« Over the last ten years, work on readability deployed sophisticated NLP techniques, such as syntactic parsing and statistical language modeling, to capture more complex linguistic features and used statistical machine learning to build readability assessment tools. […] Yet ...

more ...

A note on Amazon’s text readability stats

Recently, Jean-Philippe Magué advised me of the newly introduced text stats on Amazon. A good summary by Gabe Habash on the news blog of Publishers Weekly describes the perspectives and the potential interest of this new software : Book Lies: Readability is Impossible to Measure. The stats seem to have been available since last summer. I decided to contribute to the discussion on Amazon’s text readability statistics : to what extent are they reliable and useful ?


Gabe Habash compares several well-known books and concludes that the sentence length is determining in the readability measures used by Amazon. In fact, the readability formulas (Fog Index, Flesch Index and Flesch-Kincaid Index, for an explanation see Amazon’s text readability help) are centered on word length and sentence length, which is convenient but by far not always adapted.

There is another metric named ‘word complexity’, which Amazon defines as follows : ‘A word is considered “complex” if it has three or more syllables’ (source : complexity help). I wonder what happens in the case of proper nouns like (again…) Schwarzenegger. There are cases where the syllable recognition is not that easy for an algorithm that was programmed and tested to perform well on English words ...

more ...

About Google Reading Level

Jean-Philippe Magué told me there was a Google advanced search filter that checked the result pages to give a readability estimate. In fact, it was introduced about seven months ago and works to my knowledge only for the English language (that’s also why I didn’t notice it).


For more information, you can read the official help page. I also found two convincing blog posts showing how it works, one by the Unofficial Google System Blog and the other by Daniel M. Russell.

The most interesting bits of information I was able to find consist in a brief explanation by a product manager at Google who created the following topic on the help forum : New Feature: Filter your results by reading level.
Note that this does not seem to have ever been a hot topic !

Apparently, it was designed as an “annotation” based on a statistical model developed using real word data (i.e. pages that were “manually” classified by teachers). The engine works by performing a word comparison, using the model as well as articles found by Google Scholar.

In the original text :

The feature is based primarily on statistical models we built with the help of ...

more ...

Lord Kelvin, Bachelard and Dilbert on Measurement

Lord Kelvin

Here is what William Thompson, better known as Lord Kelvin, once said about measure :

« I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science, whatever the matter may be. »
William Thompson, Lecture on “Electrical Units of Measurement” (3 May 1883)


I found this quote in an early essay of the French philosopher Gaston Bachelard on what he calls “approached knowledge” (Essai sur la connaissance approchée, 1927). For him, measures cannot be considered for themselves, and he does not agree with Thompson on this point. According to him, the fact that a measure is precise enough gives us the illusion that something exists or just became real.

I quote in French, as I could find a English edition nearby, the page numbers refer to the book published by Vrin.

« Et pourtant, que ce soit dans la mesure ou dans une comparaison qualitative, il ...

more ...