Productivity and beyond: mastering the Polish genitive inflection.

This study charts the development of the genitive masculine inflection, one of the most irregular parts of the Polish case-marking system. 72 Polish children aged from 2;3 to 10;8 participated in a nonce word production experiment testing their ability to supply the genitive form and their sensitivity to the semantic factors determining the choice of ending. Results indicate that productivity, or the ability to supply the inflected form of some nonce words, emerges early: 78% of the two-year-olds were able to inflect at least one test item. However, mastery, or the ability to consistently supply the correct ending, takes considerably longer to develop, and adultlike levels of provision are not reached until about age 10;0.