Hilary Barth is a psychological scientist working in the broad area of human cognition and development. Research in Dr. Barth’s lab investigates mathematical cognition; thinking and learning about number, space, time, and probability; social cognition; and decision making. Dr. Barth’s research program draws upon work in many disciplines, with connections to perceptual psychophysics, social psychology, comparative psychology, neuroscience, behavioral economics, philosophy, and education. Most projects in her lab involve behavioral studies of preschool children, school-aged children, and adults. Undergraduate research assistants play key roles in nearly all lab projects. Currently, the lab is supported by funding from the National Science Foundation.