The acquisition of pronouns has received limited attention in the literature, and there are few studies which deal with this topic in detail. From the data available, clear and sometimes surprising patterns of uniformity and variability emerge. Previous attempts to account for these patterns have all faced similar problems, specifically in explaining the heterogeneous initial set of pronouns (first person singular, and third person singular inanimate), and in accounting for the variation that is found. In this paper I find that these previously problematic areas are readily accounted for using the hierarchy of morphological features proposed by Ritter and Harley (1998).
Hanson, R. (2000). Pronoun acquisition and the morphological feature geometry. Calgary Working Papers in Linguistics, 22(Winter), 1-14.