This dissertation investigates clitic doubling of both dative and accusative objects in adult and child language. It reports on three experimental studies designed to discover the specific distributional properties of this phenomenon, with particular attention to the effect of "rheme" and "kontrast," two distinct concepts often collapsed as "focus." Study I investigates the patterns of clitic doubling through grammaticality judgment data from adults. Findings show that clitic doubling of dative objects is obligatory, while clitic doubling of accusative objects is governed by pragmatic factors. If the object is topical, clitic doubling is obligatory. If the object is rhematic and/or kontrastive, clitic doubling is prohibited. In addition, results suggest that clitic doubling of accusative objects is not differentially affected by rheme and kontrast. Study II answers the same research questions as Study I in elicited production data and serves as a baseline for Study III. Results from Study II confirm those of Study I. Study III investigates clitic doubling of both objects with children 2;0-4;0 years in elicited production data. Generalized Estimating Equation models show that children produce clitic doubling of dative objects at adult-like rates from age 2;0. However, they do not reach adult-like performance with accusative objects even by age 4;0. Children double topical accusative objects as adults do, but they insert a clitic about 20% of the time with rhematic/kontrastive accusative objects, which adults never do. This reveals either an underdeveloped pragmatic system in children or an underdeveloped syntax-pragmatics interface: either children take more referents to be given/old than adults do or the interface between syntax and pragmatics fails to accurately read the signals from the pragmatic system. The results presented here expand the literature of clitic doubling with data from dative clitics and offer support for the modular nature of language with syntax present from age 2;0 and pragmatics or the interface between pragmatics and syntax not fully matured until after age 4;0. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]