In an ergative system of case marking, A, the more agent-like NP argument of a two-place transitive predicate, is encoded differently from S, the core argument of a one-place intransitive predicate. Any occurrence (whether consistently or in a sub-domain of a language) of such (A≠S contrastive) marking of full noun phrases has been taken as positive evidence of this feature. In Western Kati, the A argument carries an oblique case suffix --a in the past tense, while the S argument remains zero marked for case.

(1) Western Kati [bsh(w)] (Nuristani)

A majority of our sample languages display evidence of ergative alignment for nouns. The distribution is clearly subareal, with ergative alignment in the south and in the central parts of the Hindu Kush region, and the lack thereof primarily in the north.