Morphological case on nouns often expresses the syntactic and semantic relationships between clausal constituents. In this study, we investigated to what extent a unique case marker was used in the past (or perfective) for the subject argument of a transitive clause (A), vis-à-vis the subject of an intransitive clause (S), the direct object of a transitive clause (P), and a recipient (R). This is the case in Purik, as seen in ‎(1), in which the ergative case suffix ‑s is used with the subject of transitive clauses, whereas the subject of an intransitive clause is zero marked and the direct object is either zero marked or takes a dative case marker.

(1) Purik [prx] (Sino-Tibetan)

Unique case-marking of the A argument is present in a majority of the sample languages. The languages lacking this property are primarily found in the region's northwest.