Epistemic modal verbs and negation in Japanese Sign Language

Epistemic modality conveys the speaker's commitment of how likely the content of the proposition will be true. Sign languages show variation in how they express epistemicity: manually, non-manually, or a combination of both. Japanese Sign Language (JSL) uses manual modal verbs to indicate epistemic modality. In the current study, using Cinque's (1999) model of cartographic syntax as a basis, we reclassified nine modal verbs which were previously identified as exclusively epistemic into three categories (possibility, epistemic, evidential). This reclassification is done based on the syntactic (word-order) restrictions and speaker judgements about the quality of commitment entailed by each modal category. Two different JSL expressions of negation, which take different scopes, also provided a clue for identifying the different categories of modal verbs. The modal verbs discussed in this paper are used also as lexical signs, which indicates that they might have acquired modal usage as JSL developed into an established language of the deaf community over 140 years. The issue of ordering between the evidential and the epistemic modal verbs are addressed in the discussion.