Basic clause negator in Sadat Tawaher Sign Language

Sign languages (SLs) generally have several manual signs to negate sentences, usually with one sign serving as the basic clause negator and with its function being only to reverse the polarity of a clause without adding any additional semantic content. We identify the basic clause negator in Sadat Tawaher Sign Language (STSL), a SL that emerged in a single household in a small Iranian village around sixty years ago. While STSL has several manual negators, all of which may serve as sentential negators, we argue that one negator, NEGbasic, is the basic clause negator. The data includes both isolated sentence productions and story-telling elicited from native STSL signers. The evidence for NEGbasic comes from distributional frequency, semantic function, negative concord, and negative responses.