Vol. 10 No. 8 (2026): Modelling the acquisition of labile verbs in Middle English

Jordan Kodner, Achim Stein & Carola Trips. This paper applies current mathematical models of learnability (Yang 2005, 2016, Irani 2019, Li 2024) to historical data to gain a precise understanding of how children in the past learned formal aspects of language. We take the learnability of the causative-anticausative alternation as an example (Irani 2019) and address the question of how children learned the class of labile verbs in Middle English. We investigate the contact hypothesis, which argues that the well-known influx of Old French verbs of change-of-state coming into Middle English (Ingham 2020) had an effect on learning the alternation as a productive rule. Drawing on work on learnability in diachrony (Kodner 2019a, 2020, 2023b, Trips & Rainsford 2022), we present a study which applies the Tolerance and Sufficiency Principle(s) (TSP; Yang 2016) to the lexicons of Present-Day English first-language learners and to the lexicon of Middle English change-of-state and motion verbs. We evaluate the conditions under which learners would posit that all of these verbs are potentially labile using frequency-weighted sampling. Significantly, we show that both morphological change (loss of distinct causative morphology) and contact (copying of French verbs) contribute to the rise in lability. Overall, we present a new methodological pathway for historical linguistics: the combination of historical corpus linguistics with cognitively motivated computational modeling to reveal how the historical child learned grammatical rules.