Bribri media tantum verbs and the rise of labile syntax

Abstract In this article, we first show that the Bribri (Chibchan) middle voice suffix - r derives passive from active transitive and agentive intransitive verbs, as well anticausative verbs nominal adjectival roots. Second, focus on five media tantum i.e., forms synchronically carry have no counterpart without . Unlike most other these are labile, they can occur in syntactically constructions with (supra-)segmental change. After describing valence patterns which labile (MTL) occur, investigate whether: (i) their non-absolutive arguments behave like ergative phrases; whether (ii) MTL verb two-argument stems. Third, outline a hitherto unnoticed diachronic path for rise of lability small subgroup verbs.