Title: Emergence, evolution, and constraints on the lexicon of a young sign language
Abstract:
Sign languages are notable not only for being produced and perceived in a different language modality, but also because they are remarkably young compared to spoken languages. This presents an opportunity to discover how linguistic structures emerge and evolve from the earliest stages of language emergence. At the same time, the first signers of these languages do not start from a blank slate. Deaf people are embedded within sociocultural, semiotic, and visual environments that presumably provide initial input. In this talk, I present studies of an indigenous sign language in East Africa, Kenyan Sign Language (KSL) to address two overall questions. First, how have signs emerged and changed within the short lifespan of KSL—around 60 years? Second, what are the constraints on sub-lexical form within this span? Drawing from a video corpus of KSL from fieldwork in Kenya (24 deaf KSL signers; 30+ hours), and a subsequent lexical database (~2,800 signs), I present two main studies and other supporting research to address these questions.
For the first question, I compare a dataset of conventionalized gestures used by Luo speakers in western Kenya with a lexicon of KSL, finding a high proportion of gestures that have form-meaning counterparts in signs. Some of these gestural-origin signs—as well as a small set of lexical intensifiers—reveal further lexicalization and grammaticalization, demonstrating the rapid evolution of the lexicon. For the second question, I use quantitative data of minimal pairs in KSL to illustrate that perceptual biases against confusability in form (phonology) occur in the KSL lexicon. From a dataset of 461 minimal pairs, I show that signers appear to be sensitive to perceptual prominence between (i) overall phonological parameters (location, handshape, movement), as well as between (ii) phonemes and (iii) features within those parameters. This research provides evidence from another language modality in support of the perspective that language is a system of information transfer (Hume 2015), in which linguistic structures reflect trade-offs between communicative quality and efficiency (Hall et al. 2016; Wedel 2014).