Interpreting null pronouns (pro) in isolated sentences

This study - one of the first "field psycholinguistics" studies conducted in an indigenous language of North America - examined how native speakers of Odawa (Ottawa) interpret pro in isolated sentences. The results suggest that Odawa speakers assume that the identities of actors in transitive sentences with two third-person participants will conform to the general expectation that more topical argument will be more likely to be dropped, will be more animate, and also will be marked with proximate morphology, which is used along with verbal morphology in Odawa to establish thematic roles. These features are captured in a number of feature hierarchies, which are generally aligned in unmarked situations. Speakers assume that when this canonical alignment of feature hierarchies is violated, the argument that does not conform to it will be less likely to be replaced by pro. Misinterpretation rates were observed in Odawa to be higher when pro replaced arguments that did not conform to canonical alignment, and also when overt arguments were used when the features did align canonically. The authors propose that isolated sentences containing pro are assumed by native speakers to conform to hierarchy-based expectations about the identities of dropped arguments.