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., group, pocket) and pronominal signs, functioning as an independent clitic for existence and possession. These findings problematize the rigid theoretical distinction between mouthings and mouth gestures, demonstrating that spoken lexical items can be scavenged, eroded, and nativized into the visual grammar of a sign language, effectively expanding current models of grammaticalization.