Abstract An infrequently attested pattern of isomorphism between markers of valence-affecting constructions involves overlap between causatives and applicatives, with a transitivizing function, and middles, which are detransitivizing. Such synchronic overlap must be due to some feature of the development of the constructions; however, so far there has been little detailed argumentation for directionality in such cases. We consider an instance of this pattern in the South Central Tibeto-Burman languages. The representation of multiple stages of the phenomena allows us to posit directionality and motivations for the evolutionary pathways involved. Here, the source morphology developed into a comitative applicative; in some languages causative meanings emerged, and in others, the construction developed an array of middle meanings via a portative applicative bridging context. The study provides new evidence for how patterns may arise in which the same morphology marks both causative or applicative constructions, on the one hand, and middles, on the other.
Peterson et al. (Tue,) studied this question.