Mother left, Father right

Abstract Studies of diachronic change in sign languages are only available for a small number of sign languages, in part due to the scarcity of historical resources for sign languages. This article presents the first study of diachronic change in Nederlandse Gebarentaal ‘Dutch Sign Language’ (NGT) and Vlaamse Gebarentaal ‘Flemish Sign Language’ (VGT). It looks at the impact of an artificial sign system on the lexicons of the Gestel variant of NGT and the Limburg variant of VGT. The recovery of two 19th century manuscripts describing 3,000 signs and 7,000 signs of this system respectively enables us to compare this artificial system with published data for NGT and VGT from the 1950s and the present. We focus on the resilience of an artificial distinction that is not considered distinctive in other natural sign languages, i.e., an absolute left/right distinction for gender marking in kinship terms. The results show that the NGT and VGT variants have partially changed or replaced all the artificial signs, except UNCLE/AUNT, NEPHEW/NIECE in NGT and PARENTS in VGT. The partial changes shed light on the mechanisms through which artificial elements are nativized to fit the phonological system of these sign languages. The changes observed in the left/right paradigm have implications for our understanding of the distribution of laterality in sign language phonology in general. Finally, the impact of the highly restricted access to language models that were part of the strict oralist approaches in these school, and the consequent impoverished language input on diachronic change and lexical innovation are discussed.