Examining the systematic complexification assumption for expository texts in German STEM schoolbooks

An appropriate level of linguistic complexity in schoolbook texts that matches students’ reading skills play in important role in STEM-learning. According to the systematic complexification assumption the linguistic complexity should increase across Grade levels. However, only few studies examined this assumption for German STEM expository texts used in school. In the present study we investigated the systematic complexification assumption. For this, we analyzed N = 914 expository texts stemming from biology, geography, and mathematics secondary school schoolbooks regarding 13 (quantitative and qualitative) indicators of linguistic complexity. To test the systematic complexification assumption, multivariate analyses of variance with post-hoc tests were conducted. The results showed that the systematic complexification assumption can mostly be corroborated for all examined STEM subjects, when quantitative linguistic features are considered. However, when looking into qualitative features, the results become less clear. STEM schoolbook authors seem to be aware of surface-level complexity, but greater awareness is needed when it comes to qualitative features. Future studies should corroborate the present findings by examining larger text corpora and extend them to further STEM subjects.