Developmental systems science refers to the application of systems science methodologies (such as network analysis, agent-based modeling, and system dynamics) to developmental science questions, particularly those derived from a developmental systems theoretical perspective. The phrase "developmental systems science" deliberately combines "developmental science" with "systems science" and is meant to reflect the joining together of these two fields. Developmental science is an approach to the study of human development that emphasizes multidisciplinary and systemic thinking and includes the spectrum from basic to applied forms of inquiry (Lerner, 2006). Systems science refers to a family of methodologies that enable the study of complex problems and typically involve modeling and simulation.

All of the projects in REDDS are encapsulated under the umbrella of systems science including both theoretical approaches and methodologies. The projects are organized into three inter-related strands: (1) Systems Evaluation Research: The development and testing of a systems science approach to program evaluation and planning to enhance internal evaluation capacity; (2) Advancing Developmental Systems Science: Exposing developmental scientists to the potential benefits of utilizing systems science methodologies and applying systems science methodologies to developmental science questions (particularly those questions derived from a developmental systems theoretical perspective); and (3) Building the Evidence-Base in Developmental Science: Studying the effects of individual (e.g., self-regulation) and contextual factors (i.e., family, school, peers, neighborhood) on adolescent development with a focus on positive youth development.