Quantifying word informativeness and its impact on eye-movement reading behavior: Cross-linguistic variability and individual differences.

The importance or centrality of a linguistic unit to a larger unit's meaning is known to affect reading behavior. However, there is an ongoing debate on how to quantify a unit's degree of importance or centrality, with previous quantifications using either subjective ratings or computational solutions with limited interpretability. Here we introduce a novel measure, which we term "informativeness", to assess the significance of a word to the meaning of the sentence in which it appears. Our measure is based on the comparison of vectorial representations of the full sentence with a revised sentence without the target word, resulting in an easily interpretable and objective quantification. We show that our new measure correlates in expected ways with other psycholinguistic variables (e.g., frequency, length, predictability), and, importantly, uniquely predicts eye-movement reading behavior in large-scale datasets of first (L1) and second language (L2) readers (from the Multilingual Eye-tracking Corpus, MECO). We also show that the effects of informativeness generalize to diverse writing systems, and are stronger for poorer than better readers. Together, our work provides new avenues for investigating informativeness effects, towards a deeper understanding of the way it impacts reading behavior.