New research in psychology, neuroscience, cognitive science, and other fields is published every day, but the gap between what is known and the capacity to act on that knowledge has never been larger. Scholars and nonscholars alike face the problem of how to organize knowledge and to integrate new observations with what is already known. Ontologies - formal, explicit specifications of the meaning of the concepts and entities that scientists study - provide a way to address these and other challenges, and thus to accelerate progress in behavioral research and its application. Ontologies help researchers precisely define behavioral phenomena and how they relate to each other and reliably classify them. They help researchers identify the inconsistent use of definitions, labels, and measures and provide the basis for sharing knowledge across diverse approaches and methodologies. Although ontologies are an ancient idea, modern researchers rely on them to codify research terms and findings in computer-readable formats and work with large datasets and computer-based analytic techniques. Ontologies in the Behavioral Sciences: Accelerating Research and the Spread of Knowledge describes how ontologies support science and its application to real-world problems. This report details how ontologies function, how they can be engineered to better support the behavioral sciences, and the resources needed to sustain their development and use to help ensure the maximum benefit from investment in behavioral science research.