Contact-Induced Grammaticalization in Turkish Sign Language: From Mouthings to Grammatical Markers

This study investigates the contact-induced grammaticalization of the Turkish existential mouthing /var/ (“there is”) in Turkish Sign Language, proposing a novel Cross-Modal Contact Route for grammaticalization. Based on 1,024 attested existential/possessive constructions identified within a corpus of 101,908 tokens from 58 signers, we analyze the distribution of variants along a unidirectional reduction cline (/ var / > / va / > biting lips, bl). Generalized estimating equations and multinomial logistic regression analyses reveal a robust apparent time effect: while older signers retain the full spoken mouthing, younger signers predominantly use the biting lips—a visual remnant of the initial labiodental fricative [v]—indicating a change from below. Significantly, the structural autonomy of the emergent gesture is supported by 118 tokens—produced exclusively by signers aged 45 or younger (16–45)—where the bl marker attaches to non-existential hosts (e.g.,