Information structure, variation and the Referential Hierarchy

Silverstein (1976)’s hierarchy of features and ergativity (Referential Hierarchy) was proposed to capture apparent systematic variation with respect to word-class (pronouns versus nouns) in the expression of the grammatical functions Subject and Object and the semantic roles Agent and Undergoer linked to these functions. An assumption of the original hierarchy was obligatoriness of marking, rather than optionality (i.e. choice of marker or its absence). Optionality is often associated with a semantic/pragmatic force additional to straight expression of grammatical function. This additional meaning may determine reanalysis and subsequent change in the morphosyntactic expression of Subject/Object/Agent/Undergoer. Along the way, apparent counter-examples to the Referential Hierarchy may be created. To understand the counter-examples, and test the descriptive adequacy of the Referential Hierarchy, better language documentation is needed.