Chen, X. B. (2015).

Assessment of text readability is important for assigning texts of appropriate levels for readers of different proficiencies. The present research approached readability assessment from the lexical perspective of word frequencies. Three studies were conducted to test whether and how the word-level feature of word frequency can be aggregated to characterise the text-level feature of readability. Results showed that it is effective to use word frequency for text readability assessment, given that the frequency norm contains measures that accurately reflects the cognitive load involved in vocabulary perception and retrieval. This study merits itself not only in providing a better understanding of the relationship between word frequency and text readability, but also in pointing to new methods on how to better utilise textual features for readability assessment.