Referential density in discourse and syntactic typology

Narrative production experiments reveal systematic crosslinguistic differences in the preferred ratio of overt to possible argumental NPs (called here the REFERENTIAL DENSITY value) between three pro-drop languages of the Himalayas (Belhare, Maithili, Nepali). These differences can be accounted for by the degree to which morphosyntactic features of NPs, especially case features, are relevant for syntactic processing. This degree is the higher the more there are pivots or controllers of syntactic rules (e.g. verb agreement) that are defined not only on the basis of a thematic role hierarchy but also by a case feature (as when, e.g., verb agreement is blocked by quirky case on the thematically highest argument).