Hierarchy is one of the most important concepts in the scientific study of language. This dissertation aims to understand why we observe hierarchical structures in speech by investigating the cognitive processes from which they emerge. To that end, the dissertation explores how articulatory, rhythmic, and prosodic patterns of speech interact. Experimental and corpus work herein focuses on correlated variability in rhythmic and articulatory timing, and spatiotemporal interactions between contemporaneously planned articulations. The experimental observations are modeled in a dynamical systems framework in which planning processes are described by interacting waves in multidimensional fields. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]