Beyond Vocabulary: Capturing Readability from Children’s Difficulty (2023)

Abstract: Readability formulae targeting children have been developed, but their appropriateness can still be improved, for example by taking into account suffixation. Literacy research has identified the suffixation phenomenon makes children’s reading difficult, so we analyze the effectiveness of suffixation within the context of readability. Our analysis finds that suffixation is potentially effective for readability assessment. Moreover, we find that existing readability formulae fail to discern lower grade levels for texts from different existing corpora.

## introduction readability is employed as a tool for various audiences, including children and second-language users, as well as diverse tasks such as web search, recommendation, selecting textbook materials, calibrating books, text summarization, machine translation, automatic text simplification, and more @xcite @xcite @xcite . importantly, the use of readability for such tasks becomes critical when the target users are children @xcite . unlike adults, they do not (yet) have all the necessary reading skills, so children require more appropriate text according to their grade level @xcite . however, @xcite highlighted that the performance of traditional readability formulae greatly varies across different grade levels while estimating the readability of children's resources. also, they proposed a lexicon-based formula named spache-allen, which could capture readability better than other traditional formulae. generally, lexicon-based readability formulae consider sentence length and static vocabulary to determine text readability @xcite . over the years, researchers augmented here, derivational suffixes increase the complexity of the word 'availabilities', changing both its syntactic category and meaning. these static vocabularies (from 1064 to 65,669 words) to increase lexicon-based formula's performance @xcite @xcite . while looking up a word within the vocabulary, such formulae do not consider words' complex properties, such as inflectional endings and derivational suffixes. more recently, @xcite included the age-of-acquisition dataset @xcite to the original spache (1968) vocabulary in their spache-allen formula, because they considered children are taught these words over the years. importantly, children learn these words in a staircased fashion from lower to more complex words across grade levels. even though vocabulary augmentation has increased their formula's performance, it does not capture the children's staircased word learning process. researchers on literacy identified suffixation as an influential factor that affects children's reading experience @xcite . in figure 1 , we show how suffixation makes a word more complex. to the best of our knowledge, no readability research has taken into account the factor of suffixation carefully, which makes children's reading difficult. instead of increasing the size of static vocabulary to push the formulas' performance digits, we should carefully understand children's vocabulary acquisition process from literacy research for the readability assessment task. in this paper, we investigate how suffixes indicate the readability level of english text with the research question rq: how effective are ranked suffixes from literacy research for readability assessment? to answer this research question, we take advantage of prior work of @xcite , where they identified 43 derivational suffixes and ranked them in 25 discrete levels based on frequency. we posit that these ranks will help us capture the staircased word complexity that children learn over the grade levels. furthermore, we have made our suffixation approach implementation publicly available on github. foot_0 2 background and related work ## conclusion our investigation shows that findings from literacy research can help us develop the appropriate readability formula for children. we also show the current state-of-the-art readability formula for children fails to discern words with complex morphological properties. moreover, our work shows that we should consider the findings from other disciplines (e.g., education, literacy) to better capture readability to suggest appropriate text for children, a rapidly increasing user group accessing digital platforms. our word-level complexity scoring can directly support lexical simplification tasks and textlevel complexity scoring can enhance text accessibility for diverse user groups (e.g.,second-language learners or marginalized populations). besides, our novel suffixation approach can serve as a versatile feature for feature-based models across various natural language processing tasks, encompassing various domains such as information retrieval or human-computer interaction.