This Professional Development Fellowship will allow a research who has worked on philosophical and theoretical issues in the cognitive and brain sciences to visit, study, and participate in the laboratory activities of two major, interrelated neuroscience laboratories at the National Institutes of Health. In the course of the fellowship the PI will pursue two specific philosophical studies of neuroscience research. The first study concerns interlevel constraints in interdisciplinary cognitive science, examining how different disciplines studying the brain tend to inform, shape, and constrain each other. Among the constraints considered will be logical, mathematical and other technical constraints on theories and models, as well as informal ways that research perspectives, techniques, methods, results and models at one level of inquiry tend to suggest limitations or openings at another. The second study examines how multiple, related, ongoing projects of a laboratory tend to reinforce each other and their results, both through replication in the narrowest sense and through replication and extrapolation more broadly understood. Beyond these specific projects, the fellowship year will allow the PI to improve his understanding of the substance and practice of neuroscience, thus better informing his philosophical work, and, in exchange, to lend the ideas and perspectives of philosophy to the scientific investigations of the laboratories.