The purpose of this study was to examine the effects of varying the semantic content of active and passive sentences along a dimension of "personalness" on the comprehension of those sentences by preschool age children. The study focuses on a current linguistic controversy dealing with the relative adequacy of syntax-based and semantics-based theories of linguistic competence, evolving an hypothesis of "adaptive egocentrism" based on Piaget's theories of language development and preoperational thought. The subjects--homogeneous with regard to economic status, heterogeneous in race with non-white subjects distributed across age and sex groups--consisted of 120 children selected from five nursery school day-care centers in Ypsilanti and Ann Arbor, Michigan. Two experiments are reported in this study. Both lend support to the "adaptive egocentrism" hypothesis proposed by Piaget. (RB)